A few tuning questions...
Posted: Wed Aug 04, 2021 2:17 pm
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. 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
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 . 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.
Thanks, everyone, for all your help!
-Jon
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. 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
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 . 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.
Thanks, everyone, for all your help!
-Jon