Sign in to follow this  
Followers 0
Guest Guest

piston and cylinder replacement?

5 posts in this topic

Just tore down the engine to remove damaged piston and cylinder. cylinder just has a dime sized section where I guess the piston fused to it (no oil) Can the cylinder be refinished or just replaced? Before I replace these with factory parts, what is needed if I wanted to put a bigger-bore piston and cylinder into it? Can you give me the name(s) of aftermarket big-bore specialists and your opinion of putting one in.

Share this post


Link to post
Share on other sites

Check around on plating. I had a ported CR250 which I re-plated. If it wasn't ported, it would have been cheaper just to replace the cylinder.

I too have a damaged cylinder. I have heard no great news, or any news really on boring out this bike. MXA did a eval on the White Bros. overbore kit. ACCORDING to MXA, this drastically reduced bottom end life. One person on this site had his cylinder bored. It worked for him w/ no problems. I am still up in the air what to do. All my work will be done over next winter.

------------------

99 WR, all YZ mods, de-octopused, OEM YZ tank and seat, jetting by Clark.

AMA, NETRA

For clarification: WE'LL be having a KICK ASS time in Moab!! Right Mitchy & Bill?!!

Share this post


Link to post
Share on other sites

Thanks Kevin, could you define plating and porting for me? Also how are you riding if you're going to do the work later?

Share this post


Link to post
Share on other sites

I have some minor scrapes in my cylinder wall. They do not warrant repair immediately.

Plating is the Nickosil (spelling?) coating applied to your cylinder wall. Think of it as essentially a chromed bore. There are several companies out there that do this. It has been argued that some of these companies don't do a real good job at this. If this is in fact the case, you would be better off replacingthe cylinder w/ a OEM cylinder from Yamaha.

Porting on a two stroke involves cutting/enlarging the intake and exhaust ports. These ports are in the cylinder wall. On a 4 stroke, porting refers to head or valve work. No work is performed on the cylinder. On a ported 2 stroke, it behooves you to have the cylinder re-coated. Some of these port jobs go up to $300.00.

Share this post


Link to post
Share on other sites

if you've got that kind of 'skidmark in your pants' on the bore look-you can save it! you have to buy a bottle of Acid & all the safety gear. you then have to use swabs & rub it in, agitating it. you can get these things back to new. remember that Nikasil is really tough! i mean really really tough. the piston should give up if it just nipped up.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0