another issue with my rebuild!

4 replies to this topic
  • amamx19

Posted July 23, 2014 - 03:15 AM


I have the case split and cannot get the left case side off of my crankshaft. For some reason the cam chain gear on the crank won't let the main bearing slide over it, their is a little wear on the gear but not sure what to do now? How much wear on that gear is to much and should be replaced?

  • grayracer513

Posted July 23, 2014 - 06:51 AM


Try to identify the tooth or teeth that is/are too tall and buzz the burr or whatever off it with a file.  If the gear is worn that badly, you're probably going to need at least that half of the crank. 

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • amamx19

Posted July 23, 2014 - 11:32 AM


that's what I was guessing to do but figured I better ask. To tell if the gear is bad will their be slop when you put the cam chain around it?

I've also been planning on taking the case halves to work and put them in a solvent tank with mineral spirits. That won't hurt anything will it? Still got bearings in just figured I'd assembly lube them up when it goes back together.

  • grayracer513

Posted July 23, 2014 - 02:29 PM


Cleaning them in a solvent tank is fine, but be sure you thoroughly wash through the oil passages with clean solvent.  Also verify that the bearings are washed clean so the rotate freely and don't have a gritty feel when dry.  Best practice is to replace the whole set while you're there, but that adds up.  Careful inspection and your best guess is called for.  Be critical and selective.  New mains, new balancer shaft bearings, and the left side main shaft bearing (yes, the one in the blind hole) are on the top of the "don't reuse unless they're near perfect" list.

  • amamx19

Posted July 23, 2014 - 04:18 PM


alright thanks! My uncle tried to rebuild the motor for me last winter so I already replace a bunch of bearings and have less the 2 hrs since then. I tore it back down because he didn't fix the transmission issue I was having ( drops out of 5th ). The bearings feel smooth, but don't really wanna tear the motor down again for awhile.

Related Content


Should I buy this bike? help....... by Numsa Hul

Dirt Bike   General Dirt Bike Forums   What bike should I buy?
  • * * * * *
  • 10 replies

Chubby dad, looking at bikes , First trip to the orange/black forum ! by Slow_ride

Dirt Bike   Make / Model Specific   KTM   250-530 EXC/MXC/SXC/XC-W/XCR-W (4-Strokes)
  • Hot  28 replies

Wilson the Blue Privateer by jetfuel

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  50 replies

05 yz450f not fast enough by RedeyeYZ

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  38 replies

Yamaha YZ450F 2017 by Chris.GVS

Yamaha YZ450F 2017
  • * * * * *
  • 1 review
  • Last review by Tommyk_55
  • On January 15, 2017

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.