hi speed vibration at the seat !!!

[LITTLEWOLF]

HI guys I've been reading all over the forum and don't see any info that might address this issue.
when I ride at higher speeds I feel a high frequency vibration. not so much at the handle bars but more at my seat.
here are the stats. 1987 k100. 80k on the clock
1. valves adjusted
2. throttle bodies balanced
3. timing adjusted and perfect
4. bike idles and revs beautifully
5. injectors serviced at (Mr. injector)
6. 93 octane (only)
7. new dual sport tires. (balanced)


I can't produce the vibration when revving on the center stand . only while riding!


Six months ago I replaced the rear main seal , and I suspect the clutch might not be perfectly aligned ?
I'm wondering if the clutch would produce these vibrations ? it only happens above 55 miles per hour.


if it was the clutch wouldn't it affect the bike at all speeds / rpms?


Second issue:
I think the timing chain tensioner  isn't producing enough pressure to tension at higher RPMs.
1. I replaces all the plastic parts in the assembly. it doesn't rattle at any RPM when on the center stand . ONLY under load.
when I'm riding , it starts to get noisy above 3000 rpm and when engine braking.  I would imagine it would be noise consistently.
but only when riding and after the bike warms up. has anyone else encountered this issue ? next step replace the metal curved tensioner as I don't see how the hydraulic spring loaded tensioner can fail . ( unless you guys know otherwise)
Please advice! its getting nice out and I want to ride !!!


Thanks in advance for any of your help / expertise !


-Wolf

[The Mighty Gryphon]

Balance your rear tire.

Have you disassembled the tensioner to see if it is clean and working smoothly?  Tension is a function of oil pressure.  Is the oil passage plugged?

[timewolf]

Balance your rear tire.


1. You think that will do it? I hope its as simple as that. Ill get i balanced again right away.

Have you disassembled the tensioner to see if it is clean and working smoothly?  Tension is a function of oil pressure.  Is the oil passage plugged?

2. Yes when i disassembled it i cleaned it up. there was no blockages, and movement seemed right. But i have no point of reference since this is my first k100.
On another threat i read about the plastic square area under the arched tensioner where the hydraulic tensioner pushes against, wears away from the oil hole pressure over years of oil flowing through. Mine was damaged and a small chunk was missing as was described in the thread. So to see if that was the issue i put some jbweld putty and filled and sanded it smooth as a patch. Then used a plastic resin apoxy to coat the area to protect and give a similar surface to the original. i think it worked for a day. It ran like a sewing machine. Then the next day it went back to noisy. opened it back up. The repair i made didnt fail. Maybe the repair i made is not smooth enough and not creating a good backstop for the oil to create pressure sufficient to create tension at high rpms. Its weird that when not in gear, there is no noise! its perfect. only under load. i think replacing the part is the next step.

[johnny]

greetings...

31 years old and only at 80k... it just wants to be ridden fast and far... id getts some no corn ethyl and lotts of techron in there and give it what it wants...

j o

[timewolf]

greetings...

31 years old and only at 80k... it just wants to be ridden fast and far... id getts some no corn ethyl and lotts of techron in there and give it what it wants...

j o

Johnny!


I totally agree and would love to ride" fast and far"! But the vibration and noisy timing chain are not exactly comforting ;)
Any thoughts of wisdom to add ?
Thanks in advance !

[The Mighty Gryphon]

greetings...

31 years old and only at 80k... it just wants to be ridden fast and far... id getts some no corn ethyl and lotts of techron in there and give it what it wants...

j o

Looks like a frappe brick, so the far part probably won't happen.

[Laitch]

Any thoughts of wisdom to add?

Try all this. Although the bike being discussed in that response is an '85, the author concludes that his bike has less vibration than later K100 models. If the timing chain is noisy and bothers you, you should inspect the rail and tensioner assembly.

[timewolf]

Looks like a frappe brick, so the far part probably won't happen.

HAHA! no sir , i would never call it a frappe racer. she is naked, but set up for comfort . saddle bags and all!
upright riding position for 2 ;)

[Scott_]

What does your drive shaft look like.
Spline conditions(both final drive input shaft and drive shaft), is the drive shaft u-joint smooth when flexing.
How is the final drive fluid, any side/side play in the rear wheel.

Just thinking of a couple of things not mentioned yet.

[alexis291]

Are you happy the wheel balance is correct, particularly the rear? I have had vibration problems where wheels were not balanced properly when new tires were fitted.

[johnny]

f that... needs to be sprayed down with pb blaster...  get 5 gallons of the liquid stuff and put it in a bug sprayer... spray everything except seat and grips... then back to back to back 500+ mile days with two 20oz bottles of techron in each tank of no corn ethyl... 

[caveman]

I'm going to suck up to jo on this one (: .


I have had a low mileage (18,000) 1988 k100lt for a couple of years and just could not warm up to it because it just wanted to buzz (bad at 4 to 5 k rpm). Took it on a trip last week, a little over 5,000 mile in 9 days with some good hard running, and it is not my imagination the bike has smoothed out a good bit.