2 questions motor rebuild

11 replies to this topic
  • 02YZ426

Posted September 03, 2009 - 03:48 PM


Doing the bottom end on my 07 450. It was making quite a racket all of a sudden and I found there to be .003 endplay in the crank, doesnt seem like much but it cant be any good. Is that enough to cause a bad rattling noise? I also need to know if the piston pin is supposed to be a slide fit or tight fit? Thanks

ps also wondering if its easier to put the top end on after I bolt the bottom end in the frame... or can I just build the whole thing and it fits back in ok?

  • grayracer513

Posted September 03, 2009 - 04:05 PM


Crank end play will rarely make any noise at all. The end play is entirely controlled by the right main bearing. .003" is not unusual.

The wrist pin fits with from .0005" to .001" clearance in both bores, so it should slide, snugly. What can happen is that the retainer clips can roll up a slight burr at the outer edge of their grooves and make it difficult to move the pin past it.

It's definitely easier to assemble the top on the bench, but it's hard to hold the engine while torquing the head. Neither choice is without its down side. If you have a good way to anchor the engine, I'd do it on the bench.

  • 02YZ426

Posted September 03, 2009 - 04:16 PM


So maybe the rod bearing is still good. hmmmm. well already ordered a new crank assembly. When the motor was together if I put it at TDC and rocked it back and forth I could hear the clunk clunk. Now that the cylinder is off I dont hear it anymore. Just noticed the endplay. Guess I will keep tearing into it... hope I find my noise lol.

  • grayracer513

Posted September 03, 2009 - 04:33 PM


The rod bearing is completely unrelated to crankshaft end play. Where/how did you see play in which parts?

  • 02YZ426

Posted September 03, 2009 - 05:09 PM


The rod has play up and down .003 on the needle bearing. Its the only play I can find so far

  • grayracer513

Posted September 03, 2009 - 06:38 PM


That is not crankshaft end play.

There is very little accurate way of measuring rod bearing clearance, which is what you're talking about. The manual calls for rocking the small end of the rod from side to side while preventing the big end from sliding on the crank. If the rod eye moves side to side in excess of 1mm (.039"), it's too loose.

End play on any shaft is the amount of free travel along the shaft axis, left to right on your crankshaft. The amount the rod moves sideways on the crank pin is rod side clearance. Learn the terminology before you ask about it, and you'll get better answers.

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  • 02YZ426

Posted September 03, 2009 - 06:52 PM


I will measure it tomorrow then and see what it is... Pretty sure it has to be out of spec. Can't see any amount of play in a rod bearing being good. It will oviously always have some side play but up and down can't be normal I wouldn't think

  • 02YZ426

Posted September 06, 2009 - 05:22 AM


I have a mystery washer in this bottom end :busted: This washer only seems to fit the shaft behind the crankshaft drive gear but the manual doesnt show one there, nor the parts book. If I dont have the washer behind the gear the wear marks dont line up on both gears so I put it there anyway.

This washer definitely came from the clutch side case because when I turned the motor over to take the crank case bolts out it fell on the bench. What has me baffled is that the crank gear lines up better without the washer there, but definitely had to be there because of the wear marks on the gears. I bought this bike new so nobody has messed with this before. Is it possible it was a mistake from the factory?

  • grayracer513

Posted September 06, 2009 - 08:08 AM


If you are speaking of the oil pump idler gear that drives the oil pump, that gear goes directly against the case, then a washer goes over it, then a snap ring. The kick start idler gear is the same way.

  • 02YZ426

Posted September 06, 2009 - 08:37 AM


Its the gear that bolts directly to the crankshaft. The washer spaces between the bearing and gear, thus aligning the wear marks on the gear to match

  • grayracer513

Posted September 06, 2009 - 08:51 AM


Sounds as if it was added. Normally, there is not a washer/spacer there, and normally, the drive gear doesn't align perfectly with the driven gear.

  • 02YZ426

Posted September 06, 2009 - 10:42 AM


without the washer the 2 gears align perfectly with each other but the wear marks do not. So Im going to leave the washer there but dont like the fact its not supposed to be there. Thanks for your help.:busted:

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