Bonneville America Forums Forums Technical Forums General Tech Cyclic vibration II.....now i'm getting desperate

I posted this a couple hours ago, then the forum went down. When it came back the thread was gone and i dunno if it had to do with the forum crashing or if it was deleted for some reason. Anyways heres the post as i originaly posted.....

Well, it wasn't the chain after all. I didn't change the rear sprocket but i'm sure it's not that because the teeth are barely worn at all......very hard to see anything. I DID buy one, but MAW decided to give me the wrong part # so i now have a sprocket for some other bike.

In any case, the chain is now new and it still does it. I'm unsure at this point if it does it with the engine disengaged via the clutch. At first i thought it didn't, then did, now i'm m just not sure. But if it does it's so slight it could be placebo. but for those who don't know the details via the first thread, i had new tires mounted and when i put the wheels back on and went for a ride this cyclic vibration that feels like a stretched chain happens. It's only detectable at about 20-25 MPH and most obvious while deceleratig, tho i can feel it while cruising at a steady 20-25 too, tho not quite as bad. It's not the chain adjustment or alignment because i've tried various adjustments ad nausium and it never happened before.I also check the wheel/tire by spinning it on the jack and it seems straight.

My latest thought is the cush drive rubber. Even tho it looks new (only at 9k) i noticed a good deal of play just now as i was putting the chain on. At least a 1/4" if not a half. Could be even more but i didn't really take too much notice. Can this cause the symptoms i decribed? If so i suppose i can stick some pieces of rubber in there to reduce the play, but i really don't want to go to all that trouble after all i've been thru unless someone can tell me it's fairly likely. Then again maybe i should anyway because i do get a lot of chain snatch when hitting the throttle in lower gears. by the way, anyone have thoughts on shimming the rubbers? i was thinking of using rubber car mats or inner tubes or such. And i figure if i shim the side that is NOT the side that takes the pressue when you give it throttle, the material wouldn't need to be anything special since it's only purpose would be to keep the slack out of it so the side that takes the hit is always right up against the dividers. Thoughts?
Any thoughts you all have would be appriciated because i'm at the end of my rope with this. Thanks.

My first thought was to use liquid silicon, but that might be messy to reverse if this is not your problem. How about getting old cush drive rubber from a junkyard and slicing it up? At least then it would be the right type of rubber and easily removed if that's not the problem. Best of Luck.

Can you be sure whether the vibration is from the front or the back? My boss has a Goldwing and had the same thing happen after a dual tire change. Turns out he had a problem with the front alignment slightly off and the head bearing under torque. Same vibrations as you describe and worst @ 20-25 mph range in a slowing turn. Just some thoughts. Good luck.

Erwin

I suppose it could be, but i would think it's unlikely because it's easily felt when under power and with the clutch pulled it may not do it, or at least so little if it does i have a hard time telling. I will check the front tho since you mentioned it because you never know. Something very obvious might show so it's worth a check anyways.

i decided to do the cush drive anyways tho because i really hate that slop in the drive So while i'm doing that i will re-check everything and see what i can find. If i'm lucky the cush drive will be bthe culprit of the vibration, but i doubt it.

nothig wrong with wishing.

Just to verify you said cyclic vibration which would indicate an occilation. positive its not a vertical(up/down)or lateral vibration(L/R)?

I can't say. All i can describe it as is a vibration i can feel mainly in the footpegs i would say. Same kind of viobration i think that you would feel if the chain is stretched and is too tight in the tight spots. But as i said it got a new chain. And i cannot feel it at all except at speeds under 20-25 and it's much more obvious while decelerating, a bit obvious if at a steady 20-25 mph or under, and hardly at all or maybe even not at all when accellerating. I'm going out now to check everything i can and shim the cush drive. One thing i keep wondering about is whether theres wsome spacer or something missing from the rear when i took the wheel off. But i don't thinks so. On the sprocket side theres only a spacer thats pushed into the hub and on the brake side that one that looks like a top hat. Then of course the one inside the hube that falls out when you remove the sprocket hub.

Ok, now i have some more info and thoughts. First, the cush drive is fine. It doesn't have the play i thought it did. Dunno if i spaced or what, but it's probably less than 1/8". I put it all back together after cleaning and greasing everything. Balanced the carbs and replace rubber manifold cap. Went for a ride and heres what i noticed. The vibration seems only to happen in 2nd gear. I cannot seem to make it happen in any other gears at any speed during decel or anything. My tranny should be fine tho because i've never been hard on it and it never has problems going into gear or any of that, and i change my oil religously with good oil. Second, the rear brake....it gets hotter than the front even tho i use the front more. I felt the disc and the caliper abd both were probably 3 times as hot as the fronts. Then again, the rear is a single while the front has two discs so maybe thats why.......they share the load. Plus why would a warped rotopr, which is the suspect thing there, not cause it in other gears even at the same speeds or with the clutch in? Any thoughts? I'm really out of ideas besides those, but the most suspicious thing is the fact it only does it in second gear. If it is the tranny this bike is as good as gone cuz i'm not about to spend the money to have the engine torn down. That would probably be 2 grand.

Is your cush rubber still in one piece or did you have to put all the individual pieces back in? If one of the rubber pieces is in crooked or twisted, or maybe fell out during re-assembly, sprocket would either be crooked or some sections would be cushioned more or maybe none at all as wheel rotates. I guess you double checked caliper bracket and its properly seated in that square notch. Whatever it is, if it worked before, its probably something simple.

Caliper is in the notch, rubbers are all in right and not damaged at all. I'm really at a loss when considering the fact it only does it in second. Kinda scary when i think about it because i don't see what it could be other than internal. Unless maybe in second it just sets up just the right resonace for whatever is causing it. Thats my only hope, but i've eliminated everything i can think of to the best of my abilities. I keep coming back in to check the thread, but i've been out there trying various things all morning.

I'm starting to think this is a low speed fuel problem and that the reason for it happening only in 2nd in a 10 mph range between about 15 and 20 mph has something to do with the pilots and the resonance at that speed/gear. I checked the plugs and it's running rich. I tried playing with the screws to no avail, so i'm thinking maybe a pilot is loose. Then again that would only make one cylinder rich, but i guess i'll check the pilots anyways. I changed them to 45's a few weeks ago then back to stock when the 45's were too rich. I think i tightened them fine and it ran fine after that. But if one came loose that might cause it. Or if one is partially clogged, tho that wouldn't cause richness. But that may be a seperate issue. Funny, it's been running fine since my last rejet months ago according to the plugs till now.

One more observation. I notice the vibration is almost exclusivly felt thru the footpegs. If i take my feet of the pegs its almost hard to tell if it's doing it.

Hello, I just had a vibration that I couldn't put my finger on, I took my bike in for inspection and needed a front tire. On replacing the tire my vibration seems to be gone. Have you check your front tire thread? Scott

Yes, and it did seem to be somewhat out of round but i can't be sure. I suppose i should try a better method than i did. But if you felt the vibration i'm talking about i think you might feel the same as i do, which is that i doubt it could be the tire.Just the fact it only happens in 2nd gear between 15 and 25 MPH makes no sense since the front is not coupled to the engine in any way. I'm thinking it's the rear sprocket which i'll be changing as soon as i return the worng one i just received with the chain. If that doesn't work i'll look closer at the tire.

did you replace the front sproket too?

No, but it's pretty new because i changed to a 17 not long ago.

Ive been following this thread. I hope you figure your sh_t out soon. The suspence is killing me. Not as much as your wanting to fix the issue Im sure.

I should know if it's the sprocket this weekend, assuming one of the dealers near me has one in stock. If that doesn't do it i already talked to the online store about returning the front tire for replacement if i find it's out of round and they said no problem. I intend to rig something to the fender this week sometine to hold a pointer that i can use to detect high and low spots when i spin the tire. I think it is off, but i didn't use an accurate method so this will tell me for sure. Hoping the sprocket takes care of it tho, and i will post back when i find the problem whatever it is.

I checked my front tire today. very bad news. The tire is good, the wheel is bent. I believe the shop must have bent it when they swapped tires but they of course won't admit to it. Said it had to be a pothole. They did say they can be straigtened and i got them to agree to have it done w/o cost on thier end, but they guy they send it to will charge $80 and i'll have to pay that. I asked if he can DEFINATLY do a good job and give me back a wheel thats dead on and they said yes. I hope they're right because a new wheel is $600+, and if it doesn't work the new wheel with tax and the cost of an unsuccessful straightening will run me over $700. Nice. I just spent $250 on tires and $110 on a un-needed chain, so theres over a grand right there. Not happy. Not happy at all. And to top it off for all i know that may not even fix the vibration problem.

$600! The whole speedy wheelkit is $790.00 for front and rear! 1 spoked wheel is $600! Thats outrageous.

Anyhow, hope this fixes the problem Daz

Wow DAZ, that really sucks "rooster"!

Whats the name of the bike shop to avoid?

Long story, but i've pretty much eliminated that as being the source of the problem and the shop's responsibility. I believe it happened months ago when i hit a huge pothole. It's very slight anyways and i banged it out even more with a rubber sledge.