bad, bad, bad.....bad vibraaaations !!!!

[bitsurfer001]

Ok, its time to call on the collective for this one. This is a motor vibration, unmistakably. The motor cycles through a steadily increasing, peaking then decreasing vibration. I would say it cycles every 5 seconds or so. The bike will ride down the road, completely normal. Then, I start to feel the vibration as the turn signals begin to shake, the amplitude of the vibration increases until the whole bike is "a-buzz" and it feels like the cylinder tube and head are going to fly off the bike. The vibration will then subside as the same rate it came on. It will run perfect for the next 5 seconds then the cycle starts again. Pulling in the clutch does not effect the vibration. {don't try this next part at home} This happened 50 miles after I had the head off the bike and put it back together. My cam chain timing was off about 3 teeth when I initially installed the cams. Before I noticed I did turn the motor over by hand past the point of no return, which is when I realized the cam timing was off. I thought the resistance was due to the cams pushing on the valves, but no, it must have been the valves hitting the piston. So, lets say I have bent valves. The bike did run great for 50 miles, so I am wondering if it is something else. Would bent valves be the cause of the cyclical vibration ? Also, what if the motor was not quite at TDC when I timed the cams the second time ??? I made sure the head bolts were tight. Pete 88 KLR 90 Tengai

[RM]

On Tue, 22 Jan 2002, bitsurfer001 wrote:

>The motor cycles through a steadily increasing, peaking then decreasing >vibration. I would say it cycles every 5 seconds or so. The bike will >ride down the road, completely normal. Then, I start to feel the >vibration as the turn signals begin to shake, the amplitude of the >vibration increases until the whole bike is "a-buzz" and it feels like >the cylinder tube and head are going to fly off the bike. The vibration >will then subside as the same rate it came on. It will run perfect for >the next 5 seconds then the cycle starts again.

This suggests that you have two sources of vibaration that are not perfectly in sync with each other. The vibration effects are additive when in-phase and five seconds later they cancel each other when out of phase. Did you disassemble anything at all having to do with the counterbalancer system? Remove the chain?

[Ted Palmer]

bitsurfer001 wrote: [...]

> So, lets say I have bent valves. The bike did run great for 50 miles, > so I am wondering if it is something else. Would bent valves be the > cause of the cyclical vibration ?

I doubt it.

> Also, what if the motor was not > quite at TDC when I timed the cams the second time ???

Then it probably would not run great at all. Like RM suggests, I suspect the counterbalancer system is out of sync. Mister_T Melbourne Australia

[Bogdan Swider]

> the amplitude > of the vibration increases until the whole bike is "a-buzz" and it > feels like the cylinder tube and head are going to fly off the bike. >

Having had the experience of ridding 1000 + miles with my balancer system out of sync it seems to me you have a version of the same malady. You did the same with the valves so it seems you're at least consistent. You'll have to remove the magneto and take a look. The instructions in the manual are fairly clear. Also I can forward you some info that will further help you set the timing. Bogdan

[Ryan Newman]

> This is a motor vibration, unmistakably. > The motor cycles through a steadily increasing, peaking then > decreasing vibration. I would say it cycles every 5 seconds or so. > The bike will ride down the road, completely normal. Then, I start to > feel the vibration as the turn signals begin to shake, the amplitude > of the vibration increases until the whole bike is "a-buzz" and it > feels like the cylinder tube and head are going to fly off the bike. > The vibration will then subside as the same rate it came on. It will > run perfect for the next 5 seconds then the cycle starts again. > Pulling in the clutch does not effect the vibration.

Ok, so if you pull in the clutch at speed, and the engine goes down to idle, there is NO difference? If that's indeed the case, then I would suspect that the problem isn't with the engine at all. If you had bent valves, the bike wouldn't hardly even run, so that's not your problem. Ryan Phoenix

[Mark]

At 9:40 AM -0700 1/22/02, Ryan Newman wrote:

> > This is a motor vibration, unmistakably. > > The motor cycles through a steadily increasing, peaking then > > decreasing vibration. I would say it cycles every 5 seconds or so. > > The bike will ride down the road, completely normal. Then, I start to > > feel the vibration as the turn signals begin to shake, the amplitude > > of the vibration increases until the whole bike is "a-buzz" and it > > feels like the cylinder tube and head are going to fly off the bike. > > The vibration will then subside as the same rate it came on. It will > > run perfect for the next 5 seconds then the cycle starts again. > > Pulling in the clutch does not effect the vibration. > >Ok, so if you pull in the clutch at speed, and the engine goes down to idle, >there is NO difference? If that's indeed the case, then I would suspect that >the problem isn't with the engine at all.

Ya, if that's the case, I would lean towards a severe wheel balance problem. Does it only happen when you're rolling? Have you tested this with the engine at 4000RPM with the bike stationary? Mark B2 A2 A3

[ephilride@aol.com]

At 9:40 AM -0700 1/22/02, Ryan Newman wrote:

> > This is a motor vibration, unmistakably. > > The motor cycles through a steadily increasing, peaking then > > decreasing vibration. I would say it cycles every 5 seconds or so. > > The bike will ride down the road, completely normal. Then, I start to > > feel the vibration as the turn signals begin to shake, the amplitude > > of the vibration increases until the whole bike is "a-buzz" and it > > feels like the cylinder tube and head are going to fly off the bike. > > The vibration will then subside as the same rate it came on. It will > > run perfect for the next 5 seconds then the cycle starts again. > > Pulling in the clutch does not effect the vibration. > >Ok, so if you pull in the clutch at speed, and the engine goes down to idle, >there is NO difference? If that's indeed the case, then I would suspect that >the problem isn't with the engine at all.

Do the basics first. Tighten all bolts, starting with the engine mounts. -- knot