KDXRIDER.NET

I recently had my motor rebuild and when I got the engine back the liscensed mechanic told me that the crank is stiff but once I break it in it should be good. I want to play it safe and figure out why is it so stiff. It's almost impossible to turn to hand. Today I took the clutch side cover off and took a look at it. (This is also all with the top end off) and everything looks good. I managed to spin the crank to rotate with a ratchet and discovered when the bottom end bearing gets to its deepest point in the engine it spins mostly freely with still some friction but when the bearing gets closer to the top nearing where the top end will be it gets really stiff and almost impossible to turn. I dont have a case splitter or to much experience with bottom end. What should I do? Thanks! (Btw the bike is a KDx200 96).

Something is wrong but I can't tell you for sure what it is. The crank should spin at the same resistance all through its rotation. It could be that the crank to rod clearance isn't correct. Check the clearance at top dead center and bottom dead center.

Sounds like time for a trip back to the mechanic that did the work. What did he rebuild? Just the top, the bottom, the whole thing? Did he have the crank out? Something is binding where it shouldn't.

Im going to give him a call tomorrow. He rebuilt the bottom end only. I was thinnking maybe the bearings didnt seat properly? Idk, I will check the clearance and get back to yous.

You might try just giving each end of the crankshaft a pretty firm tap with a plastic hammer. When I used to work as a motorcycle mechanic a lifetime ago, that was standard practice once the crank was installed and the cases bolted together. It just helps all the bearings seat. It sounds like the mechanic got the cases lined up, then used the bolts to pull them together. That tends to bind the crank up. The plastic hammer treatment will often help.

If that doesn't fix it, the mechanic needs to make it right. The crank should spin easily by hand.

chkdx, great asnwer.

I second his remarks.

I just replaced my crank bearings and seals using the frozen crank method.
Everything went together fine, but I had to center the crank using a block of wood and a hammer on the clutch side before it turned smoothly. I put the crank pin at the bottom and used a wedge between the crank halves before whacking it so I didn't screw up the crank alignment. It only took a couple of whacks to do the job.
Good Luck!