re-sleeve 4stroke cylinder??

[steve.emma]

just a quick question but if the plating on a 4t cylinder was worn out OR if i wanted to do a big bore conversion could a cylinder be bored oversize (within practical limits) and fitted with a steel sleeve like is sometimes done with 2t cylinders?
im guessing it would wear faster than nickasil plating, but other than that any reason why not? cheers.

 

[Ol'89r]

im guessing it would wear faster than nickasil plating, but other than that any reason why not? cheers.

The big difference is the heat expansion rate. You would have to run much more piston clearance with the cast iron liner than you would with the plated aluminum cylinder. Since aluminum and iron expand and contract at different rates, the cast iron liner would have to have more piston to cylinder clearance.

The plated aluminum cylinder expands at a similar rate as the aluminum piston. Therefore you can set the piston clearance up tighter without it seizing. Tighter clearance means more hp. Also, the cylinder wall in a modern four stroke engine is very thin and does not allow for much of an overbore.

IMO, it would be better to have it replated.

 

[2strokerfun]

Of course, the type of engine and year would be helpful information.

 

[whenfoxforks-ruled]

If you want a bigger bore, then have it bored and replated. If you want the stock bore, have it replated or replaced.