My 2001 400EX just started vibrating very badly and getting much hotter than normal. One shop said without tear down, I need a new top end. I didn't belive them so I tore the top end apart and looked at the cam, valves, piston, rings, etc... I see no damage from sand at all. The connecting rod to the piston is not loose. I do have oil on the side of the motor where the flywheel is. I don't think that is normal is it? If not, then possibly that crank bearing and seal on that side are bad allowing oil into that side of the motor, which would explain the vibration. I want to get all your ideas to look at before I get myself into trouble tearing apart the whole bottom end.

ANy ideas what could cause a very bad vibration at idle and gets worse at high revs? Is there anything in the top end that could cause a motor to veibrate that bad? There was some noise in the very top end that sounded like there was no oil in it. But the oil was full..

Please help!!!!! PLEASE... I am so lost with out my bike. It is near new. Only ridden about 8 times only in the sand!!


Thank you!!

 

ghawkman,

It sounds like the crankshaft seal and the crankshaft bearings are bad. This would cause the excess vibration you are experiencing. Time to tear down the bottom end.

 

Thanks....

Any ideas as to what could cause the bearings to go bad?? If there are bad, shouldn't I be able to pull on the connecting rod and wiggle the crank a little?

 

I don't have an answer,but you can get alot more responses at exriders.com.

 

Sand is bad, very bad if it's internal.

The right bearing (clutch side) on the crank always goes bad first. There's a slight flaw in the Honda crank and this bearing will actually spin on the crank. Bad bearing will cause your vibration.

I have also had a crank bent slightly (unnoticable to the eye) but at idle and higher rev's vibrate and cause a dry like ticking noise in the motor (like no oil) and sound like top end but was actually the flywheel spinning and hitting the pick up.

If you have add more than 20% more power to a stock EX you have to upgrade the clutch to a Hinson or other billit inner and outer hub's cause the springs and clutch plates will wear grooves in the stock ones putting alot of unwanted metal through your entire motor.

I ran my stock clutch for a year without upgrading it. But the stock clutch took out the rod bearings just slightly enough that every 10-12 revolutions it would bind alittle, luckly I noticed it was turning over alittle hard all of a sudden to start and would quit for no reason (like in about 35seconds), so I tore it down. I saved the the top end, but I couldn't get a rod kit quick enough (back order) so I ordered a complete crank plus I had to replace every gasket and bearing because of the amount of metal. $$$

You wouldn't believe how much metal I found. Replace the clutch before you add a lot of goodies
otherwise it will cost you 3 times as much.

I change my oil now every 6 hours and cut open the filter and look for metal along with checking the used oil. So far excellent.

 

Thanks for the info... I have a lot to chew on now...

Thanks again!!