low RPM vibration

[ski_guy]

Okay, now that I've got the engine and carbs all set Im moving on to a vibration problem. There is no vibration at idle or anything past 1/3 throttle. When I hold the throttle at around 1/3 open though, it vibrates pretty noticeably. I understand that I have 3 cylinders under my seat and some vibration is normal, but it seems like a bit much to me. I've read a lot about the aligment and motor mounts causing this and both of those are good. Mounts are tight and I had alignment checked at the dealer, ok. The driveshaft was also in great shape/straight, and the splines looked fine as well. My next guess would be impellar and wear ring. The impellar is stock and is in ok shape, a few nicks and scrapes but nothing missing. How much does it take to cause vibration? I plan on pulling the pump housing tonight to get a better look at the wear ring as well. Would too much clearance make this happen? How much clearance should there be?

Can carbs cause vibration at low RPM? I remeber the problem even with the old motor before I rebuilt the carbs so I doubt that is the cause, but just wanted another opinion. Am I on the right track with the impellar?

Thanks

[douglee25]

Re: low RPM vibration

Okay, now that I've got the engine and carbs all set Im moving on to a vibration problem. There is no vibration at idle or anything past 1/3 throttle. When I hold the throttle at around 1/3 open though, it vibrates pretty noticeably. I understand that I have 3 cylinders under my seat and some vibration is normal, but it seems like a bit much to me. I've read a lot about the aligment and motor mounts causing this and both of those are good. Mounts are tight and I had alignment checked at the dealer, ok. The driveshaft was also in great shape/straight, and the splines looked fine as well. My next guess would be impellar and wear ring. The impellar is stock and is in ok shape, a few nicks and scrapes but nothing missing. How much does it take to cause vibration? I plan on pulling the pump housing tonight to get a better look at the wear ring as well. Would too much clearance make this happen? How much clearance should there be?

Can carbs cause vibration at low RPM? I remeber the problem even with the old motor before I rebuilt the carbs so I doubt that is the cause, but just wanted another opinion. Am I on the right track with the impellar?

Thanks

Yes, carbs can cause a vibration, especially at low rpm's. You may want to sync them first before addressing drive line issues.

Doug

[ski_guy]

Re: low RPM vibration

Impellar to wear ring clearance is less than .0024(in.), measured in several spots. That seems to be within spec according to my shop manual. My next step I guess is to tear apart the pump housing and check out the stub shaft/bearings and seals. Any advice?

Carbs were sync'd before they were put back on. Can an incorrect mixture cause a vibration? Plugs are all looking nice and brownish and it doesnt load up or hesitate much on accell. Thanks for the reply Doug.

Rob

[Rayman]

Re: low RPM vibration

Impellar to wear ring clearance is less than .0024(in.), measured in several spots. That seems to be within spec according to my shop manual. My next step I guess is to tear apart the pump housing and check out the stub shaft/bearings and seals. Any advice?

Carbs were sync'd before they were put back on. Can an incorrect mixture cause a vibration? Plugs are all looking nice and brownish and it doesnt load up or hesitate much on accell. Thanks for the reply Doug.

Rob

CHECK ON DRIVESHAFT UP DATE KIT