05 CRF250R Engine wear

[Cabot]

I just bought an 05 CRF250R a couple months ago, but it was too cold to do anything with it yet. According to the previous owner, it had little hours on it, but you know how those used bike sales go. :blah: I decided to tear into the engine and see what I had.

Intake valves were off, not by much. I have to go one size down from 1.92mm. no problem. they passed all other tests (although I did not take the valves out of the head)

There were a couple of things that I was unsure about, and I couldn't find the answer in the manual.

1)The piston was worn on the skirts on both intake and exhaust side.

^intake side

^exhaust side
You can see in this picture you can see the black carbon (or whatever it is) is not only on the top of the piston, but extends down the side of the piston untill the top ring on the exhaust side.

I am going to replace the piston, but was just wondering if this was hinting towards another problem the engine may have.


2) The cylender had very slight wear on the bore.

You can just see it in the pictures.
I am going to get the cylender rehoned but, once again, I was wondering if this is anything I should worry about.

 

[Cabot]

3) The top of the Crank is discolored..

The piston pin does not 'rock' in the crank at all, but the book did mention something about discoloration of the crank caused by running lean heating the piston, but didn't say if it needed replacement or not.

I would REALLY rather not split the case and replace the crank.

Sorry about the long post, and my noobishness. This is my first rebuild on something besides an XR100R, and I really don't want to mess it. Riding season is less then a month away!! :ride:

 

[Rich Rohrich]

The rod color is normal. The wear on the piston and cylinder looks to be normal as well.

 

[Cabot]

Thanks Alot!
Reading around, I know you know what your talking about. So I'll take your word on it.

 

[whenfoxforks-ruled]

Precisely check all the measurements available. Crank and cylinder clearances for sure. the thrust washers went out on my sons 250f 05. Hours or rocking, he did not accurately check the thrust washer to rod clearances. He grabbed the top of the rod and wiggled it side to side and thought it was good to go, go out it did. the cylinder should clean up with a scotch brite pad, no honing needed. Measure the new piston to skirt and the ring end gaps. That new hot rod assembly appeared way better than the stock rod! Get an hour meter and properly time your engine hours.

 

[Cabot]

Allright, I will check all the measurements again! although I think I got them right the first time.. No harm in checking them again.

I was planning on getting an hour meter as well..

Thanks for the response, and the warning!