Maintenance & Technical > KX500 Original

bad engine vibration ?

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n2682:
so i got my bike out this year and took it for a ride to find that all the sudden it has a bad vibration makes your feet go numb almost i checked every engine mount to make sure it was tight checked the flywheel to make sure it didnt come apart checked the clutch side out to. i even checked the crank the best u can while still in the motor to see if there was  bad bearing ive even took the head off to see how much piston slop there was and to check if the wrist pin or rod bearing could be gettin loose all seemed to be ok ive only had the motor together for a short time on new motor the vibration came after prob 2 hours of ride time on brand new crank rod piston all new bearings threw out i rode the bike before i did the rebuild long enough to discover that it used more trans fluid than gas in a 10 min ride so i took the motor apart and found a busted case side on the bottom of the crank. well i figured might as well rebuild entire motor i put it all back together using essembly lube that i use to build are race car motors with so i dont think i had a dry bearin on start up does the kx 5 shake like this normally or do i have a major issue anyone have any idea's on what i should do im not above taken it all back apart i want a good sound running bike but i dont wanna jump the gun and blow money that i can use to make the bike look nicer thanks for any help nick from michigan!

KXcam22:
N,
  That is a concerning problem.  If i understand correctly, you replaced the rod.  I was going to suggest a broken head stay but it you checked the top end then you have already had that off and would have noticed.  The only thing I can suggest is that the crank halves may have twisted a bit on the rod pin (new rod?) putting the crank halves way out of balance.  I can't think of anything else. My K5 hardly vibrates at all.  I would wait for a few more ideas from stewart and the other engine guys before you disassemble.  You might be able to verify this with a dial indicator on the crank with just the top end off to see if each side is the same.  Hope this helps. Cam.

hughes:
Who did the rebuild on the crank? Myself I have no issue pressing out the pin and replacing the rod, but I left the turing of the crank to my bud that has the correct stand for the crank for checking run out. My 500 vibs less after my crank rebuild. Suspect crank halves

n2682:
thanks guys i had a local machine shop press the crank back together and i had the entire rotating esembly balanced i didnt have it welded because ive heard that kawi's in general go threw rods ive always been a honda guy untell i got my hands on this monster now everything in the barn is green  :-D i had them balance it because it seemed to make sence to me i dont spare any money on are race car motors so why do it to my dirt bike ill wait for a few others to respond then i guess ill pull the crank maybe the guy didnt do something right?

stewart:
what brand of piston there not all the same wieght..did some one check the striaght ness and sqaure ness of crank halves and ,,off assmbly..if so how close is it on runout and so forth

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