11 replies [Last post]
bstratton
bstratton's picture
 Offline
Joined: 08/10/2015
Posts: 120

I have my motor on the bench and the heads and barrels off. I have the motor off because I am repainting the bike. I bought the bike a year ago and rode it for a season. When extremely hot outside (90+) my left cylinder would smoke at idle so I thought I should deal with that now. Barrels look good. Pistons, Rings and cylinders look good. Plan is to replace rings on both cylinders once I determine if these are stock size or not.

Here are my questions:

1) I want to do a top end overhaul on the left head. I really just need valve guides. My compression is fine but my understanding is that new valve guides mean re-cutting the valve seats and valves - so valve job. Should I do both heads?

2) Should I just break down and do this job all the way with new pistons, rings, barrel machining and valve jobs? I don't like to mess with things that are running great.

3) Does anyone know of a machine shop in the Boston area that has experience with BMWs? I am familiar with Max BMW and have dealt with Rusty a few times - He is a great resource, but I think they farm out their machine work. I would rather go direct if possible.

__________________

Bstratton
1971 R60/5
1965 R50/2 (project)
MA

schrader7032
schrader7032's picture
 Offline
VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6427
First question...how many

First question...how many miles on the bike/engine? Second, are you doing slingers?

1) I wouldn't think that valve guides require any work on the seats. The seats are rings that are set into the head. The guide is central to the valve opening in the head. Likely the guide will need to be reamed to match the valve stem.

2) I would measure all the clearances/tolerances of the bore, pistons in the bore, ring end gaps, ring lands. Based upon that information, you would then be able to determine where you need to go.

3) And Max doesn't want to tell you where they send the stuff to I suppose. Have a look at this list:

http://micapeak.com/bmw/Airhead-Shops.html

It's primarily for Airheads, but look out to the right at the models they support. This list hasn't been updated for 3-4 years.

Then there's this list:

http://www.ibmwr.org/dealers-independent.shtml

I don't know how current this list is.

But sending heads off, even across the country is really not that big of a deal. Vech sends his stuff to Memphis Motor Werks. If cylinders need boring, consider Bore-Tech...they apply a carbide coating which effectively never wears...in the future you should only have to replace rings.

__________________

Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

bstratton
bstratton's picture
 Offline
Joined: 08/10/2015
Posts: 120
PO said odometer was not

PO said odometer was not working for a while. 70k on the odometer. Entire bike is pretty original. He thinks maybe more like 90k. He owned it for a long time.

What are slingers?

I'm going to take a ride to their shop and talk to the manager. They can get all the parts and possibly the machinist and machines for this stuff. They seem to do a lot of it. Even if they farm it out if they are confident with the machine shop it may be worth the simplicity. I have a lot of other stuff I need to do to get this thing ready for the road.

Thanks for the links, man

__________________

Bstratton
1971 R60/5
1965 R50/2 (project)
MA

schrader7032
schrader7032's picture
 Offline
VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6427
Quote: What are

Quote:

What are slingers?

Sorry, I forgot which category of bike you were talking about! By the way, what bike are we talking about?

I did a top end on my /7 at 100K miles...I was second owner since about 13K miles. When I measured the bores, they were out of spec. It was recommended to not attempt a 1st over bore on the 1000cc cylinders, and since all new BMW parts were very expensive, I went with a Siebenrock kit. I sent the heads to Ted Porter in California.

I would recommend that a shop that knows BMW heads do the work. While "it's just heads", there are tricky parts that a machinist who's done BMW heads before would know about.

__________________

Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

bstratton
bstratton's picture
 Offline
Joined: 08/10/2015
Posts: 120
Thanks - good stuff My bike

Thanks - good stuff

My bike is a 1971 R60/5

Its a short wheelbase bike and not real strong but goes pretty good. I am trying not to do much to the motor. I inspected the clutch and rear end. No sign of oil so I am going to leave it alone. just want to stop the left cylinder from smoking when it is hot.

All stock and 95% original is my understanding but I don't know enough to verify that.

I have the bike COMPLETELY torn down for paint. I will be replacing some things like spokes and chrome brackets here and there just to get it looking good but going to stay close to stock. Maybe a solo seat if the budget can handle it and some free flow mufflers. I have a new header set as the old one was beyond rusty. I got a set of hard bags with the bike and will probably install them. I like the look and it would be good to be able to carry a few things.

__________________

Bstratton
1971 R60/5
1965 R50/2 (project)
MA

bstratton
bstratton's picture
 Offline
Joined: 08/10/2015
Posts: 120
motor is back in the bike. I

motor is back in the bike. I ended up having new valves and guides installed in the heads (and the associated machine work on the seats)

Bores were in spec and clean so I honed the glaze off, cleaned the carbon off the top of the pistons, replaced rings and put it all back together. can't wait to fire it up!

The bike is all back together except headlight bucket and wiring. That should be fun. I am hoping my notes and pictures will be sufficient. One little problem I am having is figuring out the correct routing of all the cables and wiring from the headlight bucket and handlebar controls. We have a shop fairly close by that has lots of vintage bikes so I think I'll just head in there and take some better pics.

__________________

Bstratton
1971 R60/5
1965 R50/2 (project)
MA

bstratton
bstratton's picture
 Offline
Joined: 08/10/2015
Posts: 120
Just fired it up first time since re-build

Finally! I got to hear it run! Had to adjust the new points I installed while the motor was on the bench. Like most of these engines, my timing is retarded about as far as possible to deal with pinging. I didn't touch that. I did, however close the point gap just a bit to further retard the timing (in effect) because I noticed a little ping while under a heavy load in 4th gear. That seemed to work. The only work I did to the motor was to have a valve job done on the left head, honed both barrels just enough to get the glaze off, cleaned the carbon off the top of the pistons and replaced the rings. Of course base gaskets (extra thick) and head gaskets are new.

Everything looks good. Put about 30 miles on it. Ran perfectly after I adjusted the carbs. Also adjusted valves after the first ride. My right intake loosened up and started making noise so I went through all the valve clearances one more time. Runs a little rough at very low RPMs (like from a standing start) and noticed that there is a lot more "push" in the exhaust on the right than left. What I mean by that is what you feel when you put your hands behind each muffler. Lots of "pop" on the right and not much on the left. Not sure why or if that is normal so I performed a compression check after I double checked the valve clearances. Both cylinders are equally low. (about 90 psi). I am going to re-do that under correct conditions (motor warmed up - both plugs out and fully charged battery) to see if it changes at all.

Based on the Haynes book I should want a low of 123 psi and ideally up nearer 145 psi. 90 is way out of spec.

As I said, I'll re-do the compression check under the right conditions but no matter what the readings I will also wait to give the new rings a chance to settle in and do it again after a few more miles. Also planning on picking up carb rebuild kits for both carbs. Just in case I have a fuel delivery issue on the left side. I'll also check the torque on my head and cylinder bolts.

Any idea about how many miles it should take to have the new rings seal as much as they are going to?

BTW this is a 1971 R60/5 with 73500 on the odometer.

  • 20170130_091425.jpg
__________________

Bstratton
1971 R60/5
1965 R50/2 (project)
MA

schrader7032
schrader7032's picture
 Offline
VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6427
I feel that if you did the

I feel that if you did the proper break-in during the first start and ride, the rings are going to be say 80-90% already seated. Most of the abrasiveness will be overcome with oil glazing on the cylinder walls fairly quickly, so once the glazing is there, not much more seating will be taking place.

__________________

Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

bstratton
bstratton's picture
 Offline
Joined: 08/10/2015
Posts: 120
Thanks, Kurt I just did a

Thanks, Kurt

I just did a proper compression test and low and behold things look better. I ran the bike another 20 miles or so to get it all up to operating temp, then performed the check. Results are 130 psi left and 140 psi right. much better than before but wish they were closer to each other. I think I'll leave it alone for now. I'll check again after an oil change and some more miles in the warmer weather.

__________________

Bstratton
1971 R60/5
1965 R50/2 (project)
MA

mark_weiss
mark_weiss's picture
 Offline
Arizona
Joined: 11/17/2013
Posts: 171
The difference in the exhaust

The difference in the exhaust pulse pressures that you feel is likely from carburetor imbalance. Carb balance will also account for rough feel when pulling away from a stop, but will tend to even out at speed.

Mark

__________________

Mark
qualitycycleservice.com

bstratton
bstratton's picture
 Offline
Joined: 08/10/2015
Posts: 120
Thanks, Mark That makes

Thanks, Mark

That makes sense. I will go through the process of balancing the carbs. I also have two rebuild kits coming. Lord only knows when they were last refreshed.

__________________

Bstratton
1971 R60/5
1965 R50/2 (project)
MA

bstratton
bstratton's picture
 Offline
Joined: 08/10/2015
Posts: 120
So I got my parts in and

So I got my parts in and rebuilt the carbs. Not completely but what was recommended by the old timers I know. Floats and float needles. Float pivot pins. idle mixture jets. Needles, needle jets and pre-atomizers. One new throttle cable and new throttle gears (cam - chain - twist grip and gear) I was having trouble getting a smooth operation of the throttle. Plus a new left grip to math the new right grip. About $250.00 Yikes!

But what a difference! took about an hour to replace all the parts, clean everything (again) and get the basic adjustments done. After a good long ride, I went through the balancing process (shorting each cylinder - not using vacuum gauges) Took a few attempts to get the hang of it. but I must say - it runs smoother then it ever did. Especially coming gently off the line without using much throttle.

Can't wait for good weather so I can really ride it. Or maybe show it off a little!

I have to say I learned a lot during this project. My next one will be far far better from the knowledge gained over the past year. This forum was instrumental in the successes I achieved. I also found some great local sources. I owe everyone who chimed in on my few posts a great deal of thanks. I now feel like I have something to offer so I will continue to peruse this forum and offer what I can.

Thanks!

__________________

Bstratton
1971 R60/5
1965 R50/2 (project)
MA

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.