Engine tear down

Brenan225 · Post by **Brenan225** » Fri Dec 09, 2005 7:07 am

I was given an 04 CRF 80 this summer. It was my nefews but he didn't know about air filter oil and rode it in a gravel pit until it died. I got the top end off and found about a tablespoon of fine silt on top of the piston. I am comfortable with everything above the cases but I know the bottom-end needs to be at least looked at.

My question is this.

Does anybody want to help me tackle the bottom-end? I have never split cases before but don't want to pay a shop $65 an hour to do something I might be able to do myself.

buggo · Post by **buggo** » Mon Dec 12, 2005 7:01 pm

I am no motorcycle expert, but am an engine mechanic, with a 4 stroke, a lot less than a 2 stroke will get to the bottom end. Just depends on the extent of the top end wear. And oil condition. I guess it depends what you intend to do with the bike!

Post by **dirtyboy** » Mon Dec 12, 2005 7:59 pm

I did the bottom end on a couple of YZ125's and a YZ250 a few years ago. If you have the Yamaha manual and are careful about how it comes apart (no hammers or pry devices), the job isn't too bad. When the cases come apart, all the gears are attached. There will be about 3 shafts with gears on them and the crank. The crank will stay in one side of the cases and the other shafts come out once the case is split.

As I recall, I needed a flywheel puller but I can't remember if I used a tool to split the cases. I think I just did it with my hands. Old age is obviously kicking in. You don't want me helping out.

Clean and inspect everything really well. It'll go back together with some silicone gasket maker between the cases and a torque wrench. You'll be master of that bike in no time.