engine vibration

[wvspeedfreak]

I need some help trying to figure out an engine vibration on Austin's drx90.If you hold the rpms to the point just before the clutch engages it vibrates badly.Just under that it is smooth and past that it is smooth.Any help is appreciated.

Also it has the highest stall springs in the clutch(red ones) just to give you an idea of the rpm range I am talking about on the vibration.Thanks.

[quad1rider]

Hey I had read a post about this before and the answer ended up being a belt issue...he changed the variator and reused the same belt and it had a different pitch and was slightly stretched

[wvspeedfreak]

Thanks for the reply.It still has the original variator in it as well as the belt.It has always had this vibration I just didn't pay much attention to it until I put his other drr together and noticed how much less it vibrates.
I changed the rear clutch with another one I had and it made no difference.I pulled the flywheel and saw no problems.I pulled the variator off and did notice it had mixed roller weights in it (3) 4.8 gram and (3) 5.4 gram.Would this cause a vibration?

[Logan #34's Dad]

I don't notice any vibration with the weights being different providing there are three of each being the same and the other three the same placed in the variator every other one.

[wvspeedfreak]

Rocky,that is how they were in there and I didn't really think that would do it but I wanted to make sure.

[Logan #34's Dad]

Got a different variator to try? Sounds like the clutch stuff to me and the only thing it sounds like you have not changed is the front variator. If thats not it then I don't know.

[wvspeedfreak]

Yeah,I would have switched it out to try that but I don't have an extra one lying around.I'll find one and see what that does.Thanks.

[mxdad423]

Hey Jason, if you don't have a spare variator laying around let me know, I have a couple of spares in the trailer I could send you one, I owe you one for the pics at High point.....Not saying they are bad but did you make sure your crank bearings don't have any play in them? Let me know.....

Kevin

[wvspeedfreak]

Hey thanks Kevin.Yes,I checked the crank bearings while I was in there as well.No play in them.I will see what I can come up with tomorrow.I may take you up on borrowing a variator........thanks again man.

[mxdad423]

No problem Jason, just let me know. I will be in Indy all weekend but if you need one I can get it shipped out to you first thing Monday.....

Kevin Smitley

[dericsdad]

Did you check the rear clutch bell? Wasn't sure if you swapped it out or not. Our rear clutch bell is about shot, and does the same thing. It has hot/hard spots in it on the surface where the clutch shoes grab, and feels just like what you are describing as it starts to enguage. I have to keep sanding it between races to smooth out the hard spots. Remember, the belt and front variator are always spinning when the engine is running on these things, not like on a snowmobile. By the way, Thanks again for the rear Elka shock Jason, It is working great on Deric's Predator! Dan.

[wvspeedfreak]

Dan,I replaced the entire rear cluch assembly,bell included.It ended up being the variator.I wanted to try one the other night when I was checking everything else but I didn't have one here to try.You are certainly welcome on the shock.Glad it worked out for you.Thanks everyone for the help.