details of boring out a cylinder

[bigbomber]

I have a 92 kx 125 collecting dust in my garage because it had a little incident with the piston and the cylinder wall got damaged. I haven't been too woried about fixing it because I usually ride my xr. Any way the school I started at this fall lets students use the machine shop so I have been wondering if I should try to fix my kx. I am just not sure what exactly is needed to bore out a cylinder. Do you just make it fit the larger piston or do you have to bore it out and then buy or make a sleeve for it. Any advice on this would be much apperciated. The point here is mainly to get a chance to get in the machine shop and learn something, but if I can get my old kx fixed at the same time then great.

 

[nickyd]

Your cylinder has an "electrofusion" bore...that is its plated. Your choices are to have it re-plated and run a new stock piston OR bore out what's there and install a cast iron sleeve....either of these options have worked in the past - the pros/cons are - the coated will last much longer than the cast iron sleeve UNLESS you scar it. The cast iron won't last as long but if you do scar it, it can be bored 2 or 3 times before its wasted. the cost for either is pretty close from my experience.

 

[viking20]

I would go for the plating.....Unless install a circlip wrong , and it pops out , or have a lot of dirt get past the air filter , the cylinder will very rarely be ruined. The steel sleeve will be different with reg. to heat transfer , and involves a lot more work.