ILLYamaRider
New member
I just did the top end on my dad's 98 VMAX XTC 500 and now there is a terrible vibration. I lost the far side piston and jug to a lack of carb cleaning. Replaced the piston with a new Wiseco one and a replacement used jug. Put new Wiseco rings on the other piston and honed both jugs. The engine seems to run great, but there is a terrible vibration only on my left foot at speeds above 20mph. The engine seems to run fine with more power and snap than it has had for years. Any concern that the Wiseco piston would have different weight than the stock Yamaha one and cause engine vibration?
While replacing the top end I did see that the bearing on the jack shaft near the secondary didn't have the set screws tight. Upon further investigation it appeared that my dad had an issue there that wore into the jack shaft some, but he only replaced the bearing. The area on the shaft near the set screws appeared to be in good shape, but there was still some gap between the bearing ID and the OD of the shaft. I tightened down the set screws, which would have put the shaft out of round on the ID of the bearing. I am thinking this is where my vibration is coming from because it doesn't vibrate badly at lower ground speeds. I just wanted to see if anyone thought the different Yamaha and Wiseco pistons would be an issue. I didn't think of it until after I had it back together.
While replacing the top end I did see that the bearing on the jack shaft near the secondary didn't have the set screws tight. Upon further investigation it appeared that my dad had an issue there that wore into the jack shaft some, but he only replaced the bearing. The area on the shaft near the set screws appeared to be in good shape, but there was still some gap between the bearing ID and the OD of the shaft. I tightened down the set screws, which would have put the shaft out of round on the ID of the bearing. I am thinking this is where my vibration is coming from because it doesn't vibrate badly at lower ground speeds. I just wanted to see if anyone thought the different Yamaha and Wiseco pistons would be an issue. I didn't think of it until after I had it back together.
i would put both the same make pistons in to start with unless they both weigh the same on a scale.
yamahamark
Member
Check to make sure clutches are tight and check drive shaft bearing and drivers to make sure they are good.
Can you move the jackshaft up and down or side to side if so that might just as well be your problem.
Can you move the jackshaft up and down or side to side if so that might just as well be your problem.
yamahamark
Member
Also running a OEM piston and a weisco piston will cause problems as one side will run hotter than the other and the weisco expands more which can cause it to cold seize. When running weiscos on trail allocations you need to bore the cylinders slightly to make up for the expansion of the wesico pistons.
super1c
Super Moderator
Not sure on if that piston will make a difference but left foot well vibration means drive bearing problem to me.