time for new cylinder?

 

Doing the top end on my '99 YX250 today, done a number of these, and
every time before I wonder if it was even necessary--never see much
wear but I keep up a pretty constant schedule of maintenance.

This time though it looks like the plating on the cylinder is worn
through to bear aluminum. There's a crescent shaped sliver at the top
of the piston travel on the intake (rear) side of the cylinder. Here's
a couple photos:

http://farm3.static.flickr.com/2771/4302975376_568ebbf696_o.jpg

http://farm3.static.flickr.com/2511/4302922894_2ba144fe89_b.jpg

At first I thought it might be a stain, so I gently wiped at it with a
little bit of 600 grit wet or dry sandpaper--you can see the scuff
marks right in the middle of the crescent. It's not a stain. Looks to
me like it's just aluminum showing through.

It looks to me like you can see the edge of the plating starting to
roll up, maybe from the edge of the top ring, along the right side
just to the left of the stud. When I run my finger over it I can just
feel a disturbance in the surface.

Anyone seen anything like this? I wonder why it would wear in such a
symmetrical way?

I don't want to leave this, right???

I'm thinking it's time for a new cylinder...

--
Charles
'99 YZ250

 



Make that "YZ" and "bare."

--
Charles
'99 YZ250

 


I don't have lots of experience or anything, but that looks repairable
to me... which should be  a lot cheaper than new and just as good if
done right???

 

HardWorkingDog asks:


I think you're correct.



Why not have it re-plated?  I've never had it done but
there are good shops to do it I hear.  Somebody will
chime in with one maybe.


Go fast. Take chances.
Mike S.

 

On Mon, 25 Jan 2010 06:24:19 -0800 (PST), sturd


I agree with Mike S to have it replated.   A new cylinder will be over
$400.  I'll loan you a bike if you want to ride with your son while
it's down.

Mike Baxter