2007 Cases split and I got some questions

6 replies to this topic
  • yamaman1

Posted August 01, 2011 - 09:35 PM


I finally got around to splitting my cases after finding broken teeth on my primary drive gear and chunks of my transmission in my bottom end. 5th gear wheel had broken off 2 of the 4 tabs on 1 side of it and my shift forks are grooved, everything else looks undamaged but Im not sure about my crankshaft. I have very very small nicks in the machined surface on the cranks, probably from the broken wheel tabs. As far as clearances go, the side clearance between the connecting rod and the crank halves should be checked with feeler gauges? Not sure how to check the small end free play either. My 2007 has 70hrs on it. Should I be replacing the bottom end bearings and crankshaft? The bike has been running great except for not being able to shift into 3rd last ride before I opened her up. Thanks

  • grayracer513

Posted August 02, 2011 - 08:11 AM


Rod side clearance can be checked with feelers or a dial. Clearance within the rod bearing is checked by rocking the rod sideways on the crank pin without allowing the rod to slide on the pin while the measurement is taken. A dial is used for this, and there is a drawing and the spec. for it in the manual on 2-7.

Small end wear will normally be visible if significant. Specs on the pin and piston bore are on 2-6, but the rod eye bore size isn't listed. The clearance as built is .001-.0015", with a service limit of .0029", and the only way to measure is snap gauges and a mike, unless you have some more sophisticated small bore measuring tools.

If the crank nicks are big enough (judgment call), you may want to have the crank alignment checked. It's always advisable to change the mains, but the trouble is that even if the bearing looks good, there's no way to really know how long they will last. When you replace them, you never know if you dodged a bullet, or threw away two years worth of service.

DO replace the trans bearings.

  • eazrider

Posted August 02, 2011 - 10:59 AM


[quote name='DO replace the trans bearings.[/QUOTE'] Also, don't forget to check the shift drum where it forces the fork into 3rd gear. If it hammered in and out of gear a bit before it failed, the drum may be damaged, ya gotta' replace everything that is worn when you have a tranny jumping out of gear, otherwise, you'll be doing it again. There should be no evidence of the shift fork "denting" the drum from jumping in and out of gear.

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  • yamaman1

Posted August 03, 2011 - 05:55 AM


Thanks Gray, I been riding YZF's for about 9 yrs and for some reason I always skipped that section in the manual. Now that I checked it correctly, it looks to be well within the limits on the crank so I will not replace that. I do want to replace the trans bearings though, what is the best way to go about that? Ive read about putting it in an oven but does the crank need to be removed to do that?

The shift drum is surprisingly undamaged, it was only the shift forks with grooves on the insides of their fingers. Im getting a better price as a package deal so Ill replace it anyway.

How does my piston and cylinder look? The marks are only visible but cannot feel to the touch. The last pic is what I pulled out, primary gear and 5th gear wheel.

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  • grayracer513

Posted August 03, 2011 - 07:17 AM


The piston looks good, but you should measure it nonetheless. New rings. The cylinder looks very good. You should make 2 or 3 quick passes at it with a 320 grit brush hone (aluminum oxide or softer abrasive), then clean it thoroughly with soapy water and a rag, followed by a wipe down with ATF.

The 5th pinion is quite a mess, eh?

  • yamaman1

Posted August 03, 2011 - 09:05 PM


Yeah the piston measures in spec, it was just the marks that I was worried about. I was thinking new rings along with a new pin and bearing.

Any tricks to get the tranny bearings in and out? Machine shop my best bet?

I cant believe that could happen to the 5th pinon like that, and if you look closely you can see a hairline crack on the other tooth that was ready to break. When it happened I was not able to shift into 3rd gear, does the 5th pinon operate 3rd and 5th gear?

  • grayracer513

Posted August 03, 2011 - 09:48 PM


All the trans bearings drive out and in simply with a hammer and a good drift punch except for the left hand main shaft bearing, which sits in a blind pocket. A lot of rental outlets will rent you a blind bearing puller, or you can take the case to a shop and have them pull it.

Heating the case to an even 250 ℉ is extremely helpful (use an oven with reliable heat control, and wear gloves). I've had that bearing drop out on the bench when I slapped the heated case down open side down on a wood surface, and it helps get the new bearings in place, too.

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