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A few tuning questions...

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Bikesmith01
Posts: 46
Joined: Sun Jul 12, 2020 4:55 pm

A few tuning questions...

Post by Bikesmith01 »

Hey everybody,
So I was here asking a bunch of questions last summer as I dove into the rebuilding of a nasty, rusty 1959 R60. Well, after plugging away all winter and spring, she's finally together and ridable.
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So, now I'm working on the tuning and perfecting and there are just a few things I'm wondering about:

1) Timing. Oh, man is timing a pain in the butt. It's so finicky. Such tiny movements make significant changes. The best thing I figured out was replacing the slot-head screws holding the points plate with hex head screws, so that I could fine-tune the timing without removing the advance unit. That way I didn't have to re-tappa-tappa the timing differential every time I did an adjustment. Game changer. The other big thing was discovering my advance unit had the wrong springs. The springs in there were too long and too firm, so timing was advanced at idle and then retarded above idle. Getting the correct ones in there made a huge difference. So, here's what I'm wondering about: I currently have the timing set so that the S-mark is exactly centered in the viewing hole at idle. But the mark scribed in the side of the viewing hole is a few millimeters higher. Maybe 3mm. Should I leave the S-mark in the center of the hole? Move it to match the scribed mark? Should I stop being such a damn perfectionist? The bike is running quite well, but not perfect. I don't know if it's because the timing is not perfect, or because of other things being wrong. It idles nicely, runs beautifully at half to full throttle, but has a little bit of roughness coming off idle and misses the occasional ignition below half throttle.

2) Carb adjustment. I actually think this might be more likely to be the source of my (really very slight) issues. I've been following Vech's technique for carb adjustment:
Run the bike on one carb at a time and adjust idle mix screw for best running. No problem. I have a timing light that tells me exact RPM, so I can very precisely adjust to max rpm. I feel like I have these really well set.
Adjust the idle stop screws to match RPM between cylinders. Again, I feel like I have this one pretty good, though I'm not as sure about it. When it's idling on both cylinders a TINY little adjustment of one idle stop seems to make a huge difference in the smoothness of the idle. So I don't know that I have it PERFECT, but it's pretty darn good. The bike idles really nicely. My service manual says to set the idle between 500 and 750. I find right around 675-700 sounds about right to me. 500 sounds like the bike is just about to die. I don't trust it at red lights :lol:
Throttle cable balance. Here's where I'm having trouble. Vech says leave the right cable alone and set the left for maximum smoothness as it comes off idle. Simple, but I can't seem to dial it in. I think the problem is that I'm having trouble identifying progress toward smoothness. I check how the bike comes off idle and it hesitates and rocks for less than a second, then gets completely smooth and lovely. I try turning the cable adjuster a quarter turn out. It seems exactly the same. I turn it a quarter turn in. Same. A full turn out. Same. A full turn in. Same. If I turn it several turns I can find a spot where the bike is noticeably rougher coming off idle, but within a 2-3 turn range I just can't notice a difference. It's almost perfect, but not totally perfect. I would suspect differential timing, but I have that down to almost nothing. Differential is not more than a couple millimeters along the circumference of the flywheel. So I think it's just throttle cable balance. But I just feel like I can't quite get there. Any tips?

3) Valves. I feel like I've got these pretty dialed. I had to readjust them every ride for a few rides as everything settled into position, but then they started holding their adjustment. I did a bit of playing with "do I want the gap firmly holding the .15mm feeler, or loosely holding it?" But I think now I have them nicely set. My question is are they supposed to be so loud? I can't hear them over about 20mph, or when the engine is getting a little shouty during acceleration. But when I'm coasting down to a stop I can definitely hear some ticka-ticka from them. My initial thought was that they weren't getting oil, but every time I remove the valve covers they have a puddle of oil in them. I tried running the bike without the valve covers. Oil didn't come shooting out, but it was certainly oozing around everywhere. I'd wipe oil away from the rockers and it would come oozing back out a second later. So it seems like I have oil there. I did see in another thread that someone used the phrase "Tappy valves are happy valves." Is this just how they are? A little tappy?

4) The transmission vents a little oil. The bolt that locks the speedo cable into place is drilled through and I get maybe a quarter-teaspoon running out of it per ride. I tried replacing the bolt with a solid one and then the same amount of oil just came out from under the speedo cable boot instead, which was messier so I put the drilled bolt back. Seems like maybe this is just how the transmission is vented and a dribble of oil is just going to come out of there? Or am I missing something here? I made a vented filler plug for the final drive that's working perfectly. Maybe I'll think about doing the same for the transmission.

Other than that are just the usual niggling things. I realize now I should have turned the brake drums while I had the wheels disassembled. The rear is great, but the front pulses a little. Not enough to make me want to do something about it :D . The front brake lever reach is a little long. I might fabricate a reach adjustment for it. Anyone have any great ideas they want to share for lever reach adjustment?
The springs mounts on the center stand seem to be at the wrong spot. When I take the bike off the stand it just rests against the ground and stays there because the springs are exactly aligned with the pivot bolts at that position. If the spring mounts were just a few millimeters higher they would pull the stand home just fine. No big deal, but slightly annoying. I might move the spring mounts at some point.

I think that's it. Other than that the bike is, amazingly, perfect. And really, really fun to ride. :D
Thanks, everyone, for all your help!
-Jon
******************************************************************
Jon the Bikesmith
1959 BMW R60
1940 Royal Enfield WD-C/O
1942 Chevy 3/4-ton special Flatbed
1985 BMW K100RS
******************************************************************

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schrader7032
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Re: A few tuning questions...

Post by schrader7032 »

Quick thoughts:

1) I wouldn't worry that much about static timing...that is used to get the bike started. Where does the full advance mark end up when you rev the engine to higher RPM? You want that to come into the middle of the window and then not move with any more RPM.

2) Not sure what "coming off idle is". I turn the throttle up a bit so there is tension on the cables. At that point, you want each cylinder running the same RPM. If one of them is higher, then slow that one down...don't speed the slower cylinder up.

3) Valve noise...sounds like too much noise. You're setting intake to 0.15mm and exhaust to 0.20mm? How much up-down movement do you have with the rocker arms? Maybe your rocker arms are moving around too much. They should be adjustable or at least the pillow blocks on the ends...loosen the head bolts, squeeze the blocks together, then retighten the nuts.

4) Transmission shouldn't be venting oil.

As I recall, the stand on my R69S doesn't come up on its own. I have to be sure and use my foot to bring it home.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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Bikesmith01
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Re: A few tuning questions...

Post by Bikesmith01 »

Kurt,
Thanks for the quick reply!

1) I don't want to rev the bike up too high since I have only 140 miles on it since boring the cylinders. I want to let it break in a little more first. However, I think at higher revs the timing seems perfect. The S starts to move up at exactly the 1200RPM where it supposed to and the F centers at 3000ish. While riding, at anything above 1500RPM or so the bike is behaving beautifully, really smooth and lovely. It's only the idle-1500 that I'm trying to dial in. Sounds like my suspicion was right that it's a matter of getting the carbs right.

2) Thank you! This is exactly the piece of the puzzle I was looking for! Even though I've been adjusting carbs at idle by RPM, for some reason I had a mental block making me think I had to adjust them on the throttle cables by some kind of mystical, zen process (Vech talks about resting his chin on the tank to feel the vibration). But of course I can still do it by RPM! I can do that! Why do I need to slow down the faster cylinder? Seems to me that as long as they ended up at the same RPM per throttle position, faster versus slower wouldn't matter. Is it to avoid having one of the cylinders end up always on throttle?

3) I'll take a look at up and down movement. I didn't think of that. Thanks!

4) Hmmm. Well, then, what's different about my transmission versus a non-leaking one? I just took a look at the photo (on MAX BMW) of the bolt that holds the speedo cable in place and they show it as vented. So if that's supposed to vent pressure from the transmission, what keeps oil from coming out of there? Actually, here's a potentially related question: How much oil is supposed to be in the transmission? My manual says 1.7 pints, but I can't actually put quite that much in. At 1.5 pints, the oil level is at the filler hole. Another .2 pints would just pour out. I figured "fill it to the filler hole" was therefore the way to go. But do I maybe have too much oil in there?

-Jon
******************************************************************
Jon the Bikesmith
1959 BMW R60
1940 Royal Enfield WD-C/O
1942 Chevy 3/4-ton special Flatbed
1985 BMW K100RS
******************************************************************

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schrader7032
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Re: A few tuning questions...

Post by schrader7032 »

The reason you want to slow the fast one down is the following...you start with each throttle cable with a small amount of slack, say 1-1.5mm. When you roll on the throttle for synching, you will loose the slack and the cable will be under tension. If you were to speed up the slow cylinder, there is the potential that you will get rid of the slack, so that when you come back to idle, that cylinder will be held high on throttle. By slowing the fast cylinder down, you're only "adding" more slack so it won't have any affect back at idle or no throttle.

As for transmission fluid, certainly only put enough in the fill hole...I believe the fill hole is angled up to you so I'd say fill to the bottom of the threads. On my /7, the fill hole is horizontal, so eventually the excess flows out. It's kind of messy, but that's the way that bike is done.

Not sure why you're building up pressure in the transmission. The vent bolt is indeed clear...it's not plugged is it? What kind of gear oil are you running in the transmission?
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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Bikesmith01
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Re: A few tuning questions...

Post by Bikesmith01 »

Kurt,
Yep, that's what I thought about why to adjust down the faster cylinder. Thanks!

On the transmission, yes I filled just to the bottom of the threads of the filler hole. I'm using 75-90 gear oil. The vent hole is clear. That's where the oil is coming out. Pressure needs to be relieved out of the transmission just because of it heating up. I'm just not sure how you'd let air escape without there being any oil in it

-Jon
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Jon the Bikesmith
1959 BMW R60
1940 Royal Enfield WD-C/O
1942 Chevy 3/4-ton special Flatbed
1985 BMW K100RS
******************************************************************

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schrader7032
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Re: A few tuning questions...

Post by schrader7032 »

Jon -

You're right that the bolt lets the transmission vent. But it is unusual for it to do what you're seeing. It suggests too much fluid or too little air, or the wrong gear oil both of which don't seem to be the case. There is a faction of people who think that running a GL4 gear oil...not GL5, you didn't say which you were using...is best for the /2 transmissions. Vech etal are concerned about the excess sulphur which might attack yellow metals. If you're running a GL5, maybe for grins, trying using a GL4...Vech certainly sells it.

The only other thing that would cause the transmission to vent I'm thinking is that the transmission oil is getting too hot. But how that would happen, I don't have a clue.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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Bikesmith01
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Re: A few tuning questions...

Post by Bikesmith01 »

I've tried both Castrol Syntrax 75-90 GL-5 and now Royal Purple MaxGear, which doesn't say if it's GL-4 or 5, but does specifically say that it's non-corrosive to yellow metals. I had the the same drip with each of them. I used the same amount with each oil, right up to the bottom of the threads of the filler hole.

My transmission is definitely heating up during riding, but not to a point I'd think of as excessive. After 30 miles, I can put my hand on the transmission case. It's hot, but not hot enough to hurt.

The only thing I can thing of is that my speedo cable bolt is clearly non-standard. It's a vented M6, but doesn't have the smaller diameter part at the tip like this bolt (https://vintagebeemerparts.com/vintage- ... 30-174-ss/). I don't know how that would make a difference, but maybe it does. Maybe I'll try the correct bolt. It's only $10. Worth a try.
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Jon the Bikesmith
1959 BMW R60
1940 Royal Enfield WD-C/O
1942 Chevy 3/4-ton special Flatbed
1985 BMW K100RS
******************************************************************

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Re: A few tuning questions...

Post by schrader7032 »

Duane discusses the /2 transmission vent here near the bottom of the page:

https://w6rec.com/bmw-2-motorcycle-tran ... nd-repair/

Just wanted to make sure you have the proper setup.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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jwonder
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Re: A few tuning questions...

Post by jwonder »

Jon,

See comments below:

1) You need to check the full advance before you ride it any more. You will NOT hurt the motor by revving it. In fact you can search the forums for break-in procedures and see my previous post on babying it too much is likely not good. You need to know if the full advance is correct before you hurt the motor. That is very important.

2) The carb adjustment is most likely your problem. Search the forum as this was just discussed at length. The bobble off idle is usually fixed by making sure both sides are idling at the same rate and the throttle cables are pulling equally at the same time. If those two things don’t fix it, turn both air screws in 1/8 turn. First do everything as outlined in my previous post that goes into the proper way to adjust the carbs.

3) Noisy valves are ok. Set the valves a bit tight and it will make it less. I have stiffer valve springs on my R69S and they make a ton of noise.

4) The link Kurt sent to Duanes site explains this. Most of my /2’s don’t have the upgraded Speedo drive and they don’t leak so don’t spend the money on that. So I would look at the seal. It’s not easy to check though and I can believe someone would install it backward by accident.

I hope this helps.
James Wonder
Vice President, Vintage BMW Motorcycle Owners
2022 BMW Friend Of the Marque
Long Island, New York

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Bikesmith01
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Re: A few tuning questions...

Post by Bikesmith01 »

The output shaft seal could absolutely be the key. It's entirely possible I put that in backwards. Guess I need to pull the transmission and check. Good thing I love tinkering on this bike :D
******************************************************************
Jon the Bikesmith
1959 BMW R60
1940 Royal Enfield WD-C/O
1942 Chevy 3/4-ton special Flatbed
1985 BMW K100RS
******************************************************************

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