Ieat4strokes Posted July 7, 2009 Report Share Posted July 7, 2009 I just made the jump to a 4 mill FAST motor, Is it normal for a 4 mill to have more vibration? At just off idle in neutral mine vibrates through the footpegs waaaay more than before..... yes all motor mounts are tight. Just wondering if any of you noticed.....or is somethin inside jacked up? Thanks Brad Quote Link to comment Share on other sites More sharing options...
Wildcardracing Posted July 7, 2009 Report Share Posted July 7, 2009 a slight amount more vibration can usually be expected. But, I highly recommend you take the flywheel back off and lap it to the crankshaft taper before you have an issue with it walking off. I would hate to see you ruin a new crank and your good flywheel. Quote Link to comment Share on other sites More sharing options...
jbooker82 Posted July 7, 2009 Report Share Posted July 7, 2009 a slight amount more vibration can usually be expected. But, I highly recommend you take the flywheel back off and lap it to the crankshaft taper before you have an issue with it walking off. I would hate to see you ruin a new crank and your good flywheel. Yea laping the flywheel makes a huge difference. I usually do a quick lap job everytime I take the flywheel off. It sure makes it harder to pull off next time though. :biggrin: Quote Link to comment Share on other sites More sharing options...
Ieat4strokes Posted July 7, 2009 Author Report Share Posted July 7, 2009 a slight amount more vibration can usually be expected. But, I highly recommend you take the flywheel back off and lap it to the crankshaft taper before you have an issue with it walking off. I would hate to see you ruin a new crank and your good flywheel. Yea laping the flywheel makes a huge difference. I usually do a quick lap job everytime I take the flywheel off. It sure makes it harder to pull off next time though. :biggrin: What exactly is a lap job and how do you do it? I have a mental picture of what yall are saying but i want to be sure.... Thanks fellas Quote Link to comment Share on other sites More sharing options...
jbooker82 Posted July 7, 2009 Report Share Posted July 7, 2009 Get some valve grinding compound. Put some on the arbor of the crank and some in the flywheel. Then put the flywheel on the crank and start spining it back and fourth. It makes sure that the flywheel and crank have an exact fit. I like to do mine with the stator plate off. That way i can clean the crank arbor good, and not get any in the seal. It would tear it up if you did. I got my valve grinding compound from napa. They have 2 different kinds. A water based, and a greased base. I would get the water based, it is easier to clean up. It also works good for getting striped scews and allend head bolts out. The screwdriver or allen wrench bites in to socket with that stuff. It feels like your going to twist the scew off before the head will strip. Quote Link to comment Share on other sites More sharing options...
VegasJeff Posted July 7, 2009 Report Share Posted July 7, 2009 I just made the jump to a 4 mill FAST motor, Is it normal for a 4 mill to have more vibration? At just off idle in neutral mine vibrates through the footpegs waaaay more than before..... yes all motor mounts are tight. Just wondering if any of you noticed.....or is somethin inside jacked up? Thanks Brad Is this the same bike that you posted in the knocking video?If so, might be something bigger going on in there. Quote Link to comment Share on other sites More sharing options...
Ieat4strokes Posted July 7, 2009 Author Report Share Posted July 7, 2009 Is this the same bike that you posted in the knocking video?If so, might be something bigger going on in there. yea it's the same bike. That's why I was asking was it normal Quote Link to comment Share on other sites More sharing options...
Ieat4strokes Posted July 7, 2009 Author Report Share Posted July 7, 2009 well I guess ima tear the motor back down and see what I can see, im about ready to ship it off.... Quote Link to comment Share on other sites More sharing options...
uwenr Posted July 7, 2009 Report Share Posted July 7, 2009 well I guess ima tear the motor back down and see what I can see, im about ready to ship it off.... Did you pick up the crank new or used, if i remember right you got it used. Degree tdc of both pistons to make sure the crank is not out of phase. Quote Link to comment Share on other sites More sharing options...
uwenr Posted July 7, 2009 Report Share Posted July 7, 2009 Just read your other post, i say you have a crank problem, lower rod bearing or main bearing or it is out of phase. Quote Link to comment Share on other sites More sharing options...
Ieat4strokes Posted July 8, 2009 Author Report Share Posted July 8, 2009 since its been welded rebuilding it i guess is out of the question, I dont have a degree wheel, Is there anyone who can check it for me?? This is, well im be quiet for now but if dude sold me a bum crank, someone gonna have to foot the bill to get it fixed or something. Can any of the major builders check em? Or can i just get it trued? Quote Link to comment Share on other sites More sharing options...
Wildcardracing Posted July 8, 2009 Report Share Posted July 8, 2009 It can still be rebuilt and/or trued again, the welding just complicates it a little because the weld has to be machined out. You can get a degree wheel for about $20 through motion pro that will work. You just need to find true tdc of both pistons and make sure they are exactly 180* of each other. Also a good idea to put a dial indicator on the flywheel side of the crank and make sure it is turning true. Any builder would be able to do this for you. The flywheel makes a pretty good knock if it comes loose from the taper, I'd check it just to be sure since you said that the bearings/rods all felt very tight and smooth. Quote Link to comment Share on other sites More sharing options...
Darthwall Posted July 9, 2009 Report Share Posted July 9, 2009 X2 on that Quote Link to comment Share on other sites More sharing options...
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