650/X-2 half moon key ?

[calvinjperez650sx]

i just bought a kawasaki 650sx off craigs list this is my first stand up jetski and after 3 hours of riding and probably 10 starts i sheared the half moon key between the flywheel and tapered shaft so i pulled the motor out cracked it open found what the issue was replaced the halfmoon key that was in 4 pieces and went back to the lake...on the second start it sheared again.... any suggestions???

 

[davy87nj]

This was happening to a friend of mine. His issue was he couldnt actually tighten the flywheel down enough, useing hand tools since it starts to spin the engine. He used the nylon rope trick down the cylinder to stop it from spinning, which I dont feel is a great idea but it worked for him. I personally use a small impact gun on my 550's, but Ive never done a 650, looks like the 650 has a bolt instead of a nut like the 550's.

 

[Seanc]

Your crank and flywheel are toast you have damaged the mating surfaces so unfortunately you need to replace the crank. It will continue to break.

 

[ChrisFiore15]

I have a good complete bottom end here if your want..crank feels good, no play etc.. .225$, with stator, flywheel, bendix, cases, and crankshaft.

 

[calvinjperez650sx]

it looks like the previous owner at some point welded the flywheel to the crankshaft but it was only spot welds that also broke along with the half moon key.... could i put a new half moon key in weld the flywheel to the crankshaft and put thread lock on the bolt that holds it all together? or is there a reason that half moon key is supposed to shear off if there is a bigger issue?

 

[WFO Speedracer]

Take the flywheel back off, go to the parts house and get some valve lapping compound, put it on the crankshaft taper and on the inside taper of the flywheel, then install the flywheel back on the crank by hand. Now take the flywheel and turn it back and forth, this is going to take a bit of work because obviously its way out of whack.

Keep doing this removing the flywheel wiping it off and checking progress till you have full contact between the flywheel and crankshaft. You can look at the surface of the crank and inside of the flywheel for clues how much more needs to be done. When you are done bot the crankshaft and the inside of the flywheel should have a nice dull machined looking finish to them.

Make sure to get both surfaces spotlessly clean , I recommend brake cleaner for this, then reinstall the flywheel with a new key and torque it to spec, that should solve your issues.