KMX 125 Cylinder

minicorsa12 · L Plate Warrior Joined: 28 May 2011 Karma :

Hello everyone new to this forum.
Was wondering about my cylinder, i have 2 barrels here one is different as it has different material in the actual cylinder walls (where piston go in)

My old one is all as one so to speak.

was reading up on boring the cylinders as mine has some grooves but some people are saying they have to be resleeved. Is that just the one that is my old one.
Can my barrel with cylinder liner be bore out?

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

pics would help...
likely 1 of them is nicosil plated & therefore cannot be re-bored, only re-plated & honed.
though it is possible to retro fit a cast iron sleeve into a nicosil plated cylinder, which can then be re-bored at a later date. it is step backwards imho.
& other is older style liner fitted? which can be re-bored.
cheers,
GAZ

minicorsa12 · L Plate Warrior Joined: 28 May 2011 Karma :

Can this be bored out then ????
https://i1183.photobucket.com/albums/x470/Ryan_Newcombe/252892_10150197237855749_575865748_7167530_2444876_n.jpg[/img]

stevo as b4 · World Chat Champion Joined: 17 Jul 2003 Karma :

That does look like it's been fitted with a liner at some point in the past. It can probably be bored out to the next oversize and a suitable piston and ring set for an iron bore fitted instead.

If this barrel is in good condition and was what came with the bike, then i guess it makes good sense to have a re-bore and new piston fitted to it.

Fitting a liner to a plated cylinder is often seen as a cheap bodge or a downgrade, as it's likely that you will have slightly less power and worse heat dissipation than with the corect for the engine design Nikasil bore. It will still run far better re-bored with new parts than a worn top end would on the original cylinder. I would expect it not to last anywhere near as long before you see serious wear compared to a good condition Nikasil plated cylinder though.

Iron/steel liners have their advantages in terms of cheap and easy repair costs and ability to help with piston lubrication etc, but none of the good sides of having a linered cylinder are anything to do with performance or cooling.