Got a custom with a 80 inch EVO with a 96 inch stroker kit. Runs pretty smooth to about 65MPH and then it turns bad. After 65MPH the bike vibrates something awfull. When I pull in the clutch the vibration stops. Pulled the motor to have it balanced. Unfortunately there is nothing wrong with the motor, everything is to specs. Ay idea as to what could be bad? Tranny? Clutch?
Thanks for any input.

 

I got bad news. I had a 90 Heritage and truly loved the bike. I dealt with the vibration as long as I could. My advice--- if you want to keep the EVO softail---never, never, ever demo an Ultra with your wife!

still wish I had the Heritage

 

Just a guess, but I think a 96 inch stroker is going to vibrate worse than an 80. My stock 80" 99 runs pretty smooth all the way to 90. My sons S&S 113 shakes pretty good. I think some are just better than others for some reason. May be just ganged tolerances. Having said all of that, make sure your motor mounts are tight, and the compensator is tight also.

 

mine is most lumpy at 60mph then she smooths out upto 85 or so.

 

First a few questions, Does the vibration go away at higher speeds??? You stated the engine was checked out and was within "specs", what specs???? The vibration went away when you pulled the clutch in, so that limits the source to the engine, primary, and part of the tranny. What shape is your primary chain and sprockets in?? How much run-out in the crank and tranny shaft, what type of primary tensioner are you using. Lastly check all engine and tranny bolts to ensure they are torqued propely and everything is aligned properly, and nothing is touching the frame like an exhaust pipe,etc.
By checking out these things and answering the questions we can probably work through this. One last question does it only do it at 65 MPH or does it do it at slower speeds in a lower gear??

 

I've got 2 of those 96ci motors in rigid mounts They are vibrators makes my rigid frame knuck feel somewhat smooth (after 4 beers )

 

If pulling in the clutch at 65 mph reduces the vibration when it allows the motor to return to an idle then it still could be in the motor.

If pulling in the clutch means the clutch and transmission are no longer under load and the vibration ceases then I'd look into the trans.

Here's the test. Pull the clutch in and rev the motor, even holding it revved up and see if while standing still the vibration is created in a certain RPM range. If the vibration shows up while standing still then I'd look further into the motor, or the clutch as possibly the problem.

With it neutral and the clutch out, try revving the motor up slowly until you hit the vibration. Some where along the way you should get a better sense of what is causing it to vibrate with out being on the bike and traveling down the road while trying to detect the vibration.

If you don't have the vibration after those tests next is the drive train and that would require it to be safely on a stand and accelerated in gear turning the rear wheel. It could be a number of issues from there.

I'm not certain if the upgrade on the motor is just simply causing more vibration than you're use to?



I'm going to guess it's the input shaft bearing on the transmission.

Be sure to read my disclaimer below ... lol