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saintclair2703
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Can't find my factory manual and I have a little bet going-
I seem to remember the manual says to re-torque the head bolts at every tune-up prior to every valve adjustment.
Yes or No? Thanks

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EuroIron
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Valve adjustment as per factory manual

ummmm St,

I think somebody said the procedure was that every bolt was backed off and retorqued before every valve adjustment

maybe that was you?

is that the same as re-torque?

don't think so

EuroIron
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Valve adjustment as per factory manual

Every 4000 miles (6000 km) with the engine cold and before adjusting valves clearances, the cylinder flange fixing nuts and the cylinder head bolts must be checked for tightness to a torque of 24 ft/lb (3.5 mkp). This work should be left to the (hahahhhaa) BMW service workshop.

Note........... nowhere does it specify backing off, removing, or loosening any of the fasteners .........

btw.......... that is from a factory manual

saintclair2703
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Valve adjustment as per factory manual

Backed of about a half turn before re-torquing- yes. Isn't that the best way to get a proper reading?

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EuroIron
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Valve adjustment as per factory manual

you'll have to prove that to me...........

I've read, understood, and performed many similar torquing and retorquing procedures while working for more than one factory dealer and nowhere in the BMW manual does it say backing off at all

much less about a half a turn

however, I can give you very valid and logical arguments why loosening a head bolt on a BMW prior to retorquing?, isn't a good idea

schrader7032
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Valve adjustment as per factory manual

"EuroIron" wrote:

however, I can give you very valid and logical arguments why loosening a head bolt on a BMW prior to retorquing?, isn't a good idea

EI -

I'd sure like to hear some... I've heard completely the opposite. You won't get the right torque reading unless the nut/threads are actively sliding...otherwise you're trying to overcome static friction which won't be the correct value. When applying the torque, don't you watch the torque value as the nut is continually tightened (OK, it's usually done in stages, but it's an example)? Once you reach the appropriate value, don't you stop? The book doesn't say to reach the torque value, stop, and then confirm the torque by trying to continue tightening. You get the right torque by measuring the value while things are in motion, not while stopped. The only way to simulate the same thing is to slightly loosen and then retighten. I've heard to only loosen maybe 1/4 of a turn.

Also, I wouldn't do this process EVERY valve adjustment. Once the valves are bedded in, I might only check the torque maybe every 10K miles...possibly longer...

Kurt in S.A.

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EuroIron
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Valve adjustment as per factory manual

Argument 1) such a procedure is not specified in the service manual

in fact, I'm digging right now to see if I can find any factory's specified "checking for tightness" procedure that calls for backing off the bolts about any fraction or whole number of a turn........... for head bolts or nuts/studs

so far.......... zilch but there are many manuals of which I do not own and plenty of engines of which I know nothing

Argument 2) show me a such a specified procedure from any valid source

Argument 3) your method specified and reasons therefore are only valid if the fastener was over-tightened to begin with

I could type here for days telling you all the things I've heard but they may not all be valid or factual

schrader7032
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Valve adjustment as per factory manual

I think we should focus on the basic process of torquing a nut....let's not worry about the "checking for tightness" at first. I contend that the process of torquing a nut from a state of zero torque is to do so while the nut is sliding on the threads. My guess is that BMW won't have specificed it this way. In fact, if you look at their manuals, they're written for mechanics who already had a required level of skill as a mechanic and the manual is written more as a reminder of specific steps or processes.

Once we've agreed on this process of torquing a nut, then we can define another process which best simulates this and might be used to "check for tightness" in a manner consistent with proper application of torque.

Kurt in S.A.

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EuroIron
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Valve adjustment as per factory manual

well even without coming to the fact that loosening the head fasteners........... about some unspecified amount......... how much seems to be anyone's guess........ does indeed bring about the highly undesirable possibility of the microscopic seal surfaces of the head gasket being broken or shifted slightly.......

in fact, everything you specify is not what is written in the factory book......... even your interval is greater by 150% and it clearly demonstrates you do not grasp why the factory specifies checking for proper tightness PRIOR to checking and adjusting clearances........ it has NOTHING to do with how well the valve has "bedded in" on it's seat

we have reached the wall

I certainly disagree that BMW specific instructions are less than concise and I also maintain they are indeed written for anyone with eyes to read......... not certified black magic wrenches possessing great mystical wrenching prowess never to be known by mere purchasers of motorcycles........ btw......... what I posted was taken directly out of an "INSTRUCTION MANUAL" that was sold with the bike and in the hand of the bike's owner

it is however amusing that in the same paragraph it specifies valve adjustment should only be performed by a BMW service center

and I can certainly show you BMW, even Porsche procedures that are extremely concise and clear, even when they are seemingly questionable or convoluted........ and nowhere in any BMW or Porsche repair or service procedures have I ever read the words "about, a cunt hair, just get it tight enough, back off some.... yada yada" or even "do this if some old blue hair says he fixed one this way and they all should be done this way"

for proper torquing procedures and why the very foundation of your recommended backing off procedure is invalid

check out the Society of Automotive Engineers

or go bend the ear of your local VoTech Mechanics shop class teacher and ask........ and then specify next you would like to discuss head fasteners in specific

if you really want to know

otherwise, feel free to continue to interpret what are actually, very concise and direct instructions handed by the factory, to all owners of these machines

schrader7032
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Valve adjustment as per factory manual

"EuroIron" wrote:

in fact, everything you specify is not what is written in the factory book......... even your interval is greater by 150% and it clearly demonstrates you do not grasp why the factory specifies checking for proper tightness PRIOR to checking and adjusting clearances........ it has NOTHING to do with how well the valve has "bedded in" on it's seat

Wow, you sure can read a lot between the lines...

OK, let's get ot the basics since you say it's very clearly written and/or well known. What is the exact procedure "for checking for proper tightness"?

Kurt in S.A.

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saintclair2703
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Valve adjustment as per factory manual

Hey UE!
If the manufacturer says to retorque the headbolts at a given interval, DO IT!! Who would know better than the those that engineer and produce them?
Early Mazdas(pre-'88 626 for example) required headbolt retorque every valve adjustment. Was a normal part of my job.
The headbolt was backed off 1/4 turn--to eliminate false torque readings from the underside of the bolt head sticking), then retorqued to spec.
This weekend I did a major service to my '81 CB750, and I did retorque the headbolts--to lessen the headgasket oil seep that was common on that series engine. I marked the socket to a fixed point, backed off the bolt, and retorqued. I noted that the final socket position was 10--20 degrees beyond the intial setting, so SOMETHING changed.
It also depends on the headbolt design--torque-to-yield or stretch bolts do not require retorqueing and should not be disturbed. Torque to yield bolts must be replaced after each use, and stretch bolts must be measured and if beyond specified length, replaced.
Terry"

Got this from a mechanicalesque friend who has little experience with BMW. Makes sense to me.

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EuroIron
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Valve adjustment as per factory manual

look guys......... show me backing off any about or specified amount as proper procedure for these engines........ I'll accept it from Porsche or VW too

from a valid source

I can sure show any of you factory manuals for certain engines that clearly state if you back off any head bolts.......... replace head gasket....... and some specify head bolts too.

I don't consider Terry a valid source, read plenty of his posts.

niall4473
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Valve adjustment as per factory manual

Hi all,
Been watching this post a couple of days and poor old EuroIron seems a bit beleagered, so can I say that in my humble opinion, he is exactly right.
People have stated, on this thread, the necessity of getting the "torque" exactly right on a head in service as if that is an end in itself.
Well, its not.
The purpose of the torque spanner is to apply a measured turning moment (torque) to the fastener, so that, taking into account the lead of the screw thread and the modulus of elasticity of the bolt, a given loading is put on it to clamp the two components (in this case the barrel and head) together. Given that many other variables can affect it (temperature, the surface characteristics of the thread, lubrication or lack of etc), that would only be achieved accurately under toolroom conditions with all new parts.
Don't get me wrong, the torque spanner is an invaluable tool which should be used wherever possible, but no one should build an altar on the workbench and worship it.
In general engineering bolt stretch is measured wherever possible, in fact British manufacturers used to publish the figures for big-end bolts etc.
Where the torque spanner really wins out is in getting the clamping pressure across joint surfaces EVEN, especially if you don't have any recommended torque figures. (Incidentally, as an apprentice I had to spend quite a while learning to tighten bolts evenly, and in sequence, until they were bang on when checked). But you can manage without it, if you have to. For instance, take a look at the Norton Dominator/Atlas head fixings, no way to use a torque spanner on some of them, and yet the head hasn't been off mine for 20+k miles. Boxer BMWs probably have the easiest heads to work on of any bike.
Back to the question above, don't fix what isn't broken. With a new head gasket, torque them down to the 25ft/lbs (for an R60 if memory serves) then, as the gasket settles down, do it again, possibly twice, at 250/500 miles then once it has stabilised leave them alone. Check tightness when you have the rocker boxes off, by applying that same torque as before, but really, if they move then there's something wrong.
By backing off the headbolts then re-torquing, if there's any corrosion in the open thread under the bolt then they might not actually be as tight as they were before you touched them. Also bear in mind that all bolts have a service life, not just the sacrificial "stretch bolts" used in cars (which are used to avoid having to re-torque like above), and by continually slackening and re-stressing them you reduce this considerably, bolts like everything else in life from advertising to sex suffer from the law of diminishing returns, and checking with a thread gauge will only tell you if they are on the point of total failure.
I was once told about a test to check bolts used in high stress applications and with an unknown history:- throw them in a bucket of water, if they sink, scrap and replace them.
Got to go to work now.

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schrader7032
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Valve adjustment as per factory manual

Niall (I think that's your name) has certainly defined the proper way to measure the torque...it's a measurement that must be done with the nut and bolt moving relative to each other. I might be reading too much into he said. He said "turning moment (torque)" of the fastener. To me that means that the torque can only be measured while the fastener is in motion. This is the only way to do it, and no manual is going to specify this process. It will simply state to torque the head bolts...it's implied that everyone knows how to apply the torque and measure the value.

I also agree with his approach for torquing the head bolts after use of a fresh head gasket. Once the gasket seats, there should be little reason for a retorque of the heads. There's still some confusion about what should be done at each valve adjustment, despite what the manual might say. Once they're stable, the head bolts tend to need little attention.

I guess a question still remains in my mind and was essentially what started this thread. It is the process of checking for tightness of the head bolts. If the proper way to measure the torque value is to read the value while the nut is moving against the threads, how then, is it possible to "check the tightness" of the existing nut/bolt union WITHOUT loosening the nut and repeating the process for torque application? If one uses the torque wrench, set for 25 ft-lbs, pulls the wrench around so that 25-ft-lbs is measured (beam wrench, clicker, whatever), you have only determined that the static friction (or torque) of the nut on the threads is at least 25 ft-lbs. It takes more torque to overcome this static condition in order to get the nut moving on the threads. Then you can measure the torque.

I certainly don't advocate completely loosening all 4 or 6 head bolts and repeating the process of retorquing the heads. This will only serve to hasten failure at some point by application of extra load cycles on the threads and associated attachments. Once tightened, the attachments see load cycles much smaller in variation, due to heating and cooling of the parts. But to loosen a single nut 1/8-1/4 of a turn, dropping the torque to maybe 75% of maximum value and then retorquing seems like the only way to know for certain what the actual torque is. And I can't see where this small reduction in torque will have any significant or measureable effect on the status or health of the head gasket. Nothing will be disturbed with 1 of 6 bolts being slightly loosened at a time. If something is affected, the cumulative affect will take so long to be noticeable that by that time, the heads will have come off for a completely different reason and the whole torquing process is started from scratch.

My understanding is that torque is a measurement done as a running or sliding movement of the nut on the threads. The only way to check for tightness is to recreate the sliding process which requires that each nut, one by one, is loosened slightly and then retorqued.

Now, I will occasionally put the torque wrench on a nut and check the tightness without loosening...if the nut moves at all, there's a big problem. If it doesn't move, I'm satisfied that probably everything is OK and I'll wait for another time to properly check the torque. I still don't know what the torque is, but it isn't loose and that's a good thing.

Kurt in S.A.

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EuroIron
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Valve adjustment as per factory manual

again, your 'sliding washers and moving on the threads' premise is incorrect

and if BMW wanted you to do this......... the procedure with it's proper sequence would be clearly laid out for you in there service manuals

why do you think BMW recommends to check the torque value of these cylinder flange nuts and head fasteners prior to doing the valve adjustment procedure?

do you think you can measure a difference in valve clearance if the bolts are at 25% of their recommended torque spec instead of spot on? short of using some NASA owned optical comparator?

now if their methods are to be questioned.......... it would be to question why they fail to recommend measuring installed stem height every 4K along with their other specified procedures........ as well as making the head so that it readily lends itself to checking this critical measurement with ease

heck....... you vintage bmw guys want to invent something useful not found in the manuals....... go invent rocker geometry stuff from the VW manuals......... try checking it sometime on your BMW...... you'll be surprised how many of yours are off by a long shot

perhaps I can even open up my offer for you to show me factory published procedures, which support your notion of how head bolts should be checked for proper torque, to include any and all air cooled engines for aircraft.........

can you pony up something if the field is made that wide open?

how about include any and all air cooled engine manufacturers?

I am waiting

Allan.Atherton
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Valve adjustment as per factory manual

I check valve adjustment and headbolt torque about every 2000 miles, and I cannot remember ever feeling "stiction" with my beam-type torque wrench. What I have frequently felt over the years, more often after rebuilds, as the pointer gets to 20 lbs, is that one or two of the bolts begin to move smoothly, so I take it to 25 lbs.

EuroIron
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Valve adjustment as per factory manual

does anyone care to speculate what it would mean if one consistently found any cylinder flange or head fasteners under-torqued at the specified intervals? assuming they were checked for tightness and corrected per the factory specifications?

I'll give you a clue, automatically assuming you should loosen these fasteners prior to retorquing totally undermines and erases the intended beneficial benchmark of this exercise and also will absolutely, to some extent anyhow, lead to premature fastener fatigue or yield.

then comes the million dollar question.......

at what point of looseness can a bolt be properly retorqued?

from 10 pounds to 25?

from 15 pounds to 25?

from 22 pounds to 25?

from 24.5 pounds to 25?

all of the above?

sure, if not BMW and every other manufacturer would have, again, given you very clear procedural instructions

saintclair2703
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Valve adjustment as per factory manual

Please, what ARE those instructions? I don't remember the manual going into that much detail. (I'm still looking for my manual, however...)

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EuroIron
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Valve adjustment as per factory manual

Every 4000 miles (6000 km) with the engine cold and before adjusting valves clearances, the cylinder flange fixing nuts and the cylinder head bolts must be checked for tightness to a torque of 24 ft/lb (3.5 mkp). This work should be left to the BMW service workshop.

you want me to put the neato stuff about feeler gauges, metric cap nuts, and things in too?

saintclair2703
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Valve adjustment as per factory manual

Hahahahaha...
That's what I thought.

I don't think people would be so patient with you if you weren't so good looking.

Now, how about a quote from the ASE folks, too. A sprinkle of MIT wouldn't hurt either. Maybe some Dr Goddard is you have him, too.

Here's one of my favorite quotes;
"Ol' doc Einstein abolished time, but they haven't got the word at Sing Sing yet."
-Archy

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EuroIron
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Valve adjustment as per factory manual

ditto kiddo

tell the long legged lady I said hullo

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Valve adjustment as per factory manual

"EuroIron" wrote:

Kurt......... the head fasteners couldn't be in any better environment and if you toy with some fasteners..... you will see it is possible to torque from 49 to 50

and even 49.5 to 50

I can show you published procedures which do actually specify backing off head bolts prior to retorquing which leaves it reasonable to assume the manufacturers are capable of specifying exact and concise procedure

bmw sure is and they don't on the airheads

E.I. -

You posted this on a different thread...not sure what 49 to 50 is?? Thought I'd bring it over here...

I talked to a BMW trained mechanic who's been working on Airheads since the '60s, /2 and later as well as the newer models. He doesn't know of a specific reference to backing off the nut, but he said this is what they were taught in school. Back it off a couple of foot-pounds, one nut at a time, and recheck the torque. It doesn't affect the head gasket...unless you were to loosen all fasteners at the same time.

Having said that, he mentioned a couple of things, which I believe makes sense. First, if this is your bike and you were the last one to set the torque, then it's reasonable to just put the wrench on the nut and show that the torque is at least the specified value. If the nut was loose, then it will get tightened to the correct value. If the nut is already at the correct torque, there's little reason to think that it got tighter. In that case, leave things alone.

Second, if this is an unknown bike and you don't know who torqued the heads previously, then it makes sense to establish the baseline torque. And the only way to do that is to individually release a few ft-lbs of torque and reset the value. After that, revert to the first point.

That seems like a reasonable approach to me. BMW didn't necessarily get things right in all situations, either on the design of the bike or in their manuals. There are service bulletins which indicate there were errors in their manuals, specifically in terms conversion from SAE to metric units. I think we need to do what makes sense to each of us...if we got it wrong, the bike will let us know, hopefully not at some inopportune moment!

Kurt in S.A.

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EuroIron
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Valve adjustment as per factory manual

back off a couple foot pounds............... is that exactly 2?

now how do you propose to do that if you don't believe a head nut can be torqued from 49 ft/lbs to 50 ft/lbs

schrader7032
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Valve adjustment as per factory manual

Come on, Euro Iron, you know I didn't mean EXACTLY 2 ft-lbs. One of the definitions in Webster's for "a couple" is an indefinite small number. It's already been stated that backing off to the tune or 1/8 or 1/4 of a turn is all that's necessary.

You said "...if you don't believe a head nut can be torqued from 49 ft/lbs to 50 ft/lbs". I didn't say anything like that. I don't know what you're talking about. And what is ft/lbs? Is that feet per pounds? What unit of measurement is that? See, I can read things too literal, too. Gotcha!! Big Grin

I don't know what engine uses 49 to 50 ft-lbs (assuming that's what you meant) on head bolts, certainly not a /2, /5, etc. Still, the idea is to lessen the torque to whatever feels comfortable, a small percentage of the required torque, so it can be retorqued with a running motion.

That's it...I think a lot of information has been provided to the original poster, if he's even still reading. You can read the manuals word-for-word, you can read things on the web, you can talk to people who have been doing this work for years. Each person should then take away what works for them. Then they go riding. Hopefully that's the case here.

Later...Kurt in S.A.

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EuroIron
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Valve adjustment as per factory manual

so if a head nut is actually torqued to 24 ft lbs

can it be directly torqued to 25 ft lbs without having to loosen it.......... a couple ft lbs or even a 1/4 turn?

based on the incorrect notions of many, any nut or bolt would have to be backed off AT LEAST 6.24 ft lbs, in order to torque if to 25 ft lbs with mathematical certainty

these guys are telling you 25% stiction

why 6.24 and not 6.25?

if 6.25 that would mean the fastener was at spec and not needing any further attention

my only point is that BMW's procedure is very specific and it does not specify backing off the head fasteners to "retorque" or check them for tightness

have you thought any more about your theory on valves bedding in/seating as opposed to why the head nuts and cylinder flange nuts are actually part of a valve adjustment?

once you understand that, then it makes it easier to understand why loosening is invalid and counterproductive......... detrimental even

so humor me and kick that about.......let's not worry so much about to back off or not to back off the fasteners for now

schrader7032
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Valve adjustment as per factory manual

"EuroIron" wrote:

so if a head nut is actually torqued to 24 ft lbs

can it be directly torqued to 25 ft lbs without having to loosen it.......... a couple ft lbs or even a 1/4 turn?

based on the incorrect notions of many, any nut or bolt would have to be backed off AT LEAST 6.24 ft lbs, in order to torque if to 25 ft lbs with mathematical certainty

these guys are telling you 25% stiction

why 6.24 and not 6.25?

if 6.25 that would mean the fastener was at spec and not needing any further attention

I think you're getting way, way too numerical here...we don't have that much information to go on. There is too much error and variables in our torquing process to be that numerical. One of my points is that the nut must be moving in order to get a true torque reading. If you can do that by backing off to 24 ft-lbs and then go to 25 ft-lbs, fine. Most likely the increase in 1 ft-lb would happen so quickly that you wouldn't have time to focus on the torque wrench before you end up at or beyond the ending value.

"EuroIron" wrote:

my only point is that BMW's procedure is very specific and it does not specify backing off the head fasteners to "retorque" or check them for tightness

To me, BMW's statement to "check for tightness to 25 ft-lbs" is NOT very specific. That's why I asked someone who was trained by BMW where they do cover the specifics on each mechanical task.

"EuroIron" wrote:

have you thought any more about your theory on valves bedding in/seating as opposed to why the head nuts and cylinder flange nuts are actually part of a valve adjustment?

once you understand that, then it makes it easier to understand why loosening is invalid and counterproductive......... detrimental even

so humor me and kick that about.......let's not worry so much about to back off or not to back off the fasteners for now

I don't recall stating a theory...I might have mixed up some words regarding things bedding in. I understand that as part of a fresh engine build, things like the head gasket are going to compress over time. Things wear in to some degree. Thus, it's necessary to reestablish the proper tension in the head bolts in order that the mating surfaces remain firmly in contact. That has to be done in order to be able to set the valves properly. The dimensional relationship between the head, cylinder, and engine must be the same otherwise setting the valves won't be accurate.

From my vantage point, the loosening approach is not invalid, counterproductive, or detrimental. OK, the loosening does create a tension load cycle in the bolt that wouldn't normally be there. But the bolt is steel, it doesn't happen that much in the life of the bolt, and the delta tension (loosened vs torqued) is so small that the fatigue of the bolt is virtually unaffected. We're operating in the elastic region of the bolt's material properties. If we were near the plasticity region, then that would be a different story. I don't know the specific grade of steel, but I'm sure basic fatigue properties of the bolt, for the small stress cycle being introduced would suggest that this process could be repeated thousands and thousands of times before failure would occur. I should live that long!!

Kurt in S.A.

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Valve adjustment as per factory manual

"Haynes BMW 2-valve Twins '70 to '96, page 1.17, under Cylinder head nut tightness and valve clearance" wrote:

4. Working in the reverse of the tightening sequence, slacken the cylinder head retaining nuts by 1/4 turn each; do not slacken them further or the rocker arms may require realighning. Working in the order of the tightening sequence, tighten the nuts to the appropriate torque setting.

While it is true that the BMW manuals -- shop and owners -- do not specify a procedure for applying torque, it's not beyond the realm of possibility that the shop manuals assume that the mechanic already knows how to perform the operation and merely calls it out to refresh his memory; and that the owners manual is not written to encourage the owner to do the work, but to understand what his local dealer is doing for the money.

If you check http://www.boltscience.com/pages/tighten.htm, you'll see that the actual torque distributed to clamping force (thread extension) can be as little as 12% of the total applied torque; the rest goes into overcoming friction on the threads and the nut face.

Since static friction has a different, and generally larger value than sliding friction, one could be excused for coming to the conclusion that applying a certain torque to a fixed nut may not guarantee that the designed clamping force is actually being applied.

The latest model BMWs don't rely on a fixed torque spec, but rather ask for continuing to turn the nut through a particular angle after reaching a specified torque. This is supposed to be much more accurate than what is possible with a simple torque spec alone. Such a specification avoids a lot of the problems related to friction.

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EuroIron
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Valve adjustment as per factory manual

I am BMW factory trained

GM and Chrysler too

Certified Master Tech

anyhow, you still have not figured out why this checking for tightness, which is quite concise, is called for every 4K

but you are getting close......... so very close in fact I'll ask you to consider what the studs thread into

however, despite how this may appear to you........ this is strictly academic and nothing personal against anyone

Darryl.Richman
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Valve adjustment as per factory manual

"EuroIron" wrote:

I am BMW factory trained

GM and Chrysler too

Certified Master Tech

anyhow, you still have not figured out why this checking for tightness, which is quite concise, is called for every 4K

but you are getting close......... so very close in fact I'll ask you to consider what the studs thread into

Well, depending on the model, we are either talking about screws that thread into cast iron cylinders, or through-studs that are mounted to the cast aluminum crankcase.

In the former situation, I can't see how multiple cycles of loosening and tightening will have much effect.

The "airhead" bikes do have a certain reputation for losing the threads in the crankcase; this has been a tidy little business for TimeCert and Helicoil.

(A dealer's mechanic pulled a stud out of my R1100RS once, as well.)

Quote:

however, despite how this may appear to you........ this is strictly academic and nothing personal against anyone

I can readily appreciate the Socratic approach to learning.

But let me ask you a question: is the torque spec in the manual to be used when initially installing a head? If it is, doesn't simple physics say that applying the torque to a loose nut possibly result in higher clamping force than would be the case if the nut were already stopped and fixed?

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EuroIron
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Valve adjustment as per factory manual

does it matter?

if the fastener has been torqued according to the specs, with a good torque wrench, and you apply the correct torque to it every 4000 miles, and it doesn't move...... all is well

if you carte blanche back off prior

you don't know all is well, or even that the fastener was correctly torqued, even if after loosening it...... the fastener has to be rotated past it's previous resting position to obtain the correct torque

why? because the fasteners nor the threaded items are made of diamond

if you replaced the BMW studs and nuts with ARP fasteners, would you follow their procedures?

they will tell you not to back off......... just hit them with the torque wrench

EuroIron
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Valve adjustment as per factory manual

Here is the bottom line

if the procedure was to loosen prior to checking for tightness

BWM, and others, are quite capable of telling you so and would do so in a very clear and concise manner

their procedures do not take into account that somebody unqualified has attempted to service the machine prior

what would BMW tell you if you said, "well I don't know if it was originally and /or subsequently correctly torqued to the published spec" ???

have your torque wrench calibrated then install and new head and/or base gasket(s) and follow their procedures

that is the BMW factory I worked for and if a technician put in writing or verbally admitted to not following specific procedure, adding to procedure, etc........ and there was a problem........ that same technician would eat it

overkill or even absolutely necessary?

probably not but academically and technically correct

unverified but allegedly Suzuki does actually specify backing off head bolts, one at a time, prior to torquing during valve checking procedures......... on one of their early 80's air cooled 550 or maybe 600 cc inlines

yet Suzuki do not specify this procedure for all their engines

look at the 650 Savage.......... specifies removing ALL cylinder head nuts in a criss cross pattern, apply oil, then reinstall and torque to spec in a criss cross pattern

this is specified to be performed prior to valve clearance check every 4000 miles, and keep in mind some of these engine/frame combos require the removal of the engine to removed the cam cover as necessary to access these nuts.......

wonder how many of them have been correctly service even by dealerships

I'll think about posting some more specs

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Valve adjustment as per factory manual

I think Darryl made a good point...the BMW manual assumes you already have factory training and the procedures are more reminders than anything. I also found the same entry in the Haynes aftermarket manual which mentioned the reverse torque on each nut. But no one is going to hold an aftermarket manual up as the gospel truth. The bike's owner manual says to check for tightness but ultimately says to have the dealer do it.

If you suggest that BMW has been very specific in their instructions, where is the precise information for how to check for tightness? They don't say either to back the nut off or to just go ahead and use the torque wrench on the nut as is. It seems to suggest that you should already know what to do, as provided in details instructions in school.

So, I think we're in a gray area. Most general purpose manuals don't really cover the subject or they suggest that you let your dealer take care of it and the official manual doesn't even touch the subject.

Finding specs for other manufacturers, engines, etc., is not going to shed any more light. Someone can always point out that it is for a different engine, materials, construction, etc., and their concepts don't necessarily apply to how BMW designed their engines to be wrenched on.

If we're looking for the final answer, we need Max Fritz to come back to us. Or have some go over to Germany and sit in the Mobile Tradition office until they can find someone who has the necessary background to tell us what BMW intended.

Kurt in S.A.

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EuroIron
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Valve adjustment as per factory manual

finding procedures specified for other engines, including BMW's own......

does indeed support that premise that the procedures are quite specific and leave no guess work as to how a tech was or was not trained

the procedure for checking for tightness is very clear to me

if you loosen it, you aren't checking it for tightness

schrader7032
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Valve adjustment as per factory manual

Well, then I guess we have a semantic thing. It might say check for tightness and if that's all it said, then I'd probably agree with you. But it says check tightness to 25 ft-lbs (or whatever the number is). That means more to me in the way I understand things. To me, that means confirm the torque is at 25 ft-lbs. I know of no other way to check it other than to loosen and retighten to 25 ft-lbs. Sure, you can put the wrench on it and it might take 25 ft-lbs but you haven't overcome the static friction so the reading means little, other than the nut is not loose, ie, tight. Once you break the static friction, then you can read the torque. If it reads 25 ft-lbs, you can stop. If it reads more, then you have to loosen and start over.

You have your way, you have your training...I understand my way, and I have no training. I'm an engineer by profession, and while this is not necessarily my speciality, the information provide through these discussions just hasn't provide enough clarity and scientific basis to alter what I do know and have studied about bolted joints. I also know that technical writing, of which writing manuals is a related field, is a difficult thing to do. It's easy to leave nuances out or assume that the reader knows as much as the writer. IMHO, I don't think any of the BMW manuals being referenced has described this process in the appropriate amount of detail for the shadetree mechanic, which I are one!

I've been taking what I've read, added my own experiences and understanding, and doing what I think is best. I guess that's the road I'm on...

Later...Kurt in S.A.

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Valve adjustment as per factory manual

In my line of work,I build some high performance turbocharged engines with over 250hp/liter,and when installing high performance connecting rods,we use the "ARP" lube that looks moly based,and this is supplied with their hardware.They stress that actual tq. is not accurate since some is loss to frictioin,so this supplied lubricant is specified to be used on the threads as well as the face of the bolt/nut so you can get a ACTUAL tq. reading of the bolt/nut.
Is this over thinking/mixing new tech with old tech,regarding this issue?
I want to accurately tq. the heads,but with the reputation of "butter heads" would the lube make too much stress on the threads??

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Valve adjustment as per factory manual

"808Airhead" wrote:

... I want to accurately tq. the heads,but with the reputation of "butter heads" would the lube make too much stress on the threads??

The butterhead deformation occurs after decades and tens of thousands of miles of containing the firing pulses at operating temperature. I have never heard it connected to the torque used on the headbolts. If you overtorque the headbolts, they will just likely pull out of the head.

schrader7032
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Valve adjustment as per factory manual

"Allan.Atherton" wrote:

If you overtorque the headbolts, they will just likely pull out of the head.

Actually, since the head bolts go into the cylinder, it would be a problem for the cylinder. Plus the cylinder is steel which is even less likely to be a problem. The head-cylinder combo is bolted to the engine case with separate bolts and studs.

Kurt in S.A.

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Valve adjustment as per factory manual

"schrader7032" wrote:

... the head bolts go into the cylinder...

A mental glitch here. There is some consequence of over-tight head bolts mentioned in a forum - maybe is was stretching or breaking of the bolts. I think it was Duane, saying it was better the bolts are under-torqued than over-torqued.

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Valve adjustment as per factory manual

"Allan.Atherton" wrote:

I think it was Duane, saying it was better the bolts are under-torqued than over-torqued.

Agreed. There's no real reason to crank on these bolts. Probably anything over 20 ft-lbs up to the nomial 25 ft-lbs will be just fine. And also long as they stay tight, that's the goal.

Kurt in S.A.

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