handlebar (& other) vibration

[Stuart Mumford]

You are the MAN! Tell the truth, was it the test ride on the 6 second nitro burning pavement ripping dirt throwing Renthal modified Big Gun sporting Kenda shod Moose skidplated Happytrail highway pegged Progressive sprung Fastline equipped "CA Stu Special" (tm) that made you do it? I just put the new brakepads on this weekend, now it is EBC-stopped, too... Congrats on the new scoot, can I ride it off a cliff? CA Stu From: scottobme@... Subject: Re: Vibration I have owned both a 98 DR 650 and now a 2001 KLR 650 and the difference in

[Tom Bowman]

All: Lotsa traffic about vibration. Some thoughts from an ex-factory service rep: - Every part on a motorcycle has a natural harmonic frequency at which it will pick up and amplify vibration coming from elsewhere, be it engine, tires, or road surface. The KLR's mirrors are particulary prone to this as they're on a fairly small diameter, long stalk that's tailor-made to induce fuzziness. Solution: shorter mirror stalks with more robust material, or rubber dampers a'la XR650L (though the rubber must be "tuned" so as to move the vibes out of the KLR's natural vibration range, which may or may not be the case). I'm very pleased with the Bikemaster "GP" mirrors installed earlier this year and would recommend them as a good, cheap, *partial* solution to the problem. - Increasing the weight at the *end* of a handlebar will - to some extent - damp the harmonic vibration in the handlebar. This can be done with bar-end weights, but the accessory kinds I've seen look to be too light to have much effect. I tried some solid steel bar stock inside mine but my design was faulty and it didn't work. Seems like it should, if you're willing to cement them in place (and if you can find round stock the proper size or are willing to turn-down some) - Loose motor mount bolts are a common cause of excess vibration. I found mine loose at the 600mile service. If allowed to run loose there can be damage to the engine cases and if bolts are over-torqued in a good-faith attempt to keep them tight, they can stretch to the point that the nuts are "bottomed", making you think they're tight when the motor is just floating around in the frame. Pay special attention to the upper engine mount. - Add-on skid plates or exhaust systems can be responsible for vibes by improper location that allows interference between the motor and other bits, transferring vibration upwards to the rider that should be absorbed in the frame. Look for interference points and correct them. - I have seen mis-manufactured frames. What happens is that the inside dimension between the frame bosses and engine cases is too large; this results in the engine bolts reaching their normal torque spec *before* the engine case is clamped properly. If you've looked everywhere else to no avail, try loosening the engine bolts up completely and examining the gaps between the frame bosses and cases: if there is more than about 0.5mm (0.020"), clearance with the bolt loosened, there may be a problem. This is fairly common on mass-produced mild steel frames due to all the welding-induced heating/shrinkage. IMHO it is extremely unlikely that an imbalance problem would be present from an improperly-indexed balancer or out-of-tolerance engine parts. Having said that, though, I'd be suspicious of vibration that appeared on a high-mileage motor, as tolerances can increase and lead to vibration in clutches, etc., even though the motor is running fine. I have never ridden a single of any brand that was vibration-free and doubt I ever will - balancers or none. My A14 seems buzzy only after I get off the R1100RT I own, yet my sense of that disappears after a few minutes "adjustment". From some of the owner descriptions in this thread, though, I suspect somebody's bike has a problem that isn't imaginary. Hope this is helpful to someone. Tom Bowman A14 "Stella"