extreme vibrations

[peterkik]

Hi

Within two weeks my Tenere vibrations increased to a level that i think something is very wrong. First it only showed when going faster (didnt matter what gear) but now it starts to show at ever lower speeds. Especially when reving up but also (but different) when closing the trottle shifting gears.
I changed the chain and sprockets and checked the rearwheel bearings but they were ok. There is a little space in the lever-system (is this correct english??) of the suspension, but i dont think that can be the source of the vibrations.
So probably the engine itself has a problem. (bearings?) Anybody has suggestions or experiences with the same problem?

Thanks

Peter

[RichLees]

Ouch! Have you noticed any loss of power or just engine vibration? I agree that it won't be the swingarm links. Did you check the bearing in the middle of the sprocket carrier on the rear wheel? Are there any oil leaks around the gearbox output shaft? Does the shaft turn freely when the bike is out of gear? Does it turn smoothly when the bike is in gear, but with the clutch in? Have you checked the oil to confirm that there is no metal in the oil?
Good luck.
Richard

[POB/London]

You can isolate it as engine (big end etc) by revving stationary out of gear. If you then pull the clutch and let the reves drop (or even cut the engine) while traveling at speed you can also isolate the rolling chassis (wheel bearings, cush drive, swingarm bushes, wheel balancing etc). Try placing a long screwdriver on the engine cases at a variety of places and listening for knocking (by pressing the other end of the screwdriver agains your skull). Are there any strange tapping noises? And how quickly did this progress? What mileage has the bike done? Is the oil clean when you change it? Do you ever have a problem with your gearshift? From what you say I would guess main bearing on it's way out, or gone. Beware, as riding like this for too long can damage bearing seats = new cases required...

Good luck.

[KlausXT600]

check correct tightness of nut on right hand crankshaft side IMMEDIATLY!
check also woodruff key there.
if this is o.k., check bearings.

klaus

[peterkik]

Hi,

Checked the nut and (un?)fortunatly nothing wrong there. I don't know what a woodruff key is.... :-(
Looks like I will have to take the whole engine apart. Well, it has done over 80.000 km in 3 years (with no real problems) so I was expecting an overhaul quite soon anyway.

Thank all of you for you advices
(and please tell me what a woodruff key is :-)

Peter

[RichLees]

a woodruff key is peg that is used to align a component at the right angle on a shaft: the shaft and component each have a slot in line with the axis of the shaft. the slot is on the outside of the shaft and the inside of the component and the woodruff key goes in the hole that is created when the two slots are aligned. the nut is there to lock the component in place so if the nut is tight, the key will (almost) certainly still be there.
keep us posted!
Richard

[KlausXT600]

thanks richard,
won't be able to explain it better than you.
peter, you can refer also here:
http://216.37.204.202/Yamaha_OEM/Yam...pe=13&A=20&B=4
(microfiche/crankshaft assy., no. 6 and 25)
so, if everything is o.k. with the right hand crankshaft side, you should check the main bearings and the bearing of the connecting rod (wich means total dismounting of engine :-( ).
with this milage it's very likley that the bearings are gone.

klaus

[peterkik]

Thanks Richard and Klaus,

The woodruff key (funny name. in dutch it's called: spie (which is funny too), whats it in German?) is indeed still there. Im going to check the rest on the righthandside, but whatever I find now i'll have to take the whole engine apart.
In a way im looking forward to it because its the first time to overhaul a 600 engine (done a couple of XT500's and a XR500 already).
And timing could be worse: its still summer, just finished building my garage and i can use my girlfriends bike for going to my job.
I'll keep you posted on what I find.

Thanks again

Peter

[david lambeth]

Severe vibration from xt6s is often caused by a loose swing arm spindle nut and lower engine mount (allows engine to rattle against frame)
I have seen this problem on many high mileage bikes - if the problem is left too long the swing arm bearings will need re shimming to avoid the arm going tight on re-tightening.