125-200cc piston sizing

http://www.ebay.co.uk/itm/MITAKA-Pi...84?pt=UK_Motorcycle_Parts&hash=item35dd27fa38



my bike has the original cylinder on it and about 18000 miles, it's been through 4 pistons so far, atm it has a pro x which the garage put on, they also honed the cylinder. If I have now done 4500 miles or 160 hours on the piston, I want to replace it soon [though it still starts first kick and has bags of power but I heard cast pistons fail and mess up the crank. Assuming my cylinder is not scored or damaged when I remove it, what piston size do I get? Will it make a massive difference if I choose a b c or d size, and is it worth having it honed again? the ebay link is to the pistons whose seller told me to go for a c size piston but I read b c and d were only for oversizing, ie, for replated barrels, not just used barrels

The only way to know is to measure it with a bore gauge (not calipers), subtract the recommended piston clearance from the manual, and that is your piston size.

Do you know if your cylinder is original gilasil or has it got a cast iron liner in it? If its gilasil then dont hone it, and get an internal bore guage on it.
What are the exact sizes of piston available i see the listings for 53:95 if the next size up is 53:96 then no i wouldnt worry about sticking the slightly larger one in its only 0.01 larger.
Thats just me tho, pro x are a good brand i had Mitaka in my kmx for 3years who knows the miles parts for that bike were so cheap i honestly didnt care if i blew the engine up.

Are you just replacing out of worry for 160 hours?

Oh and when a piston fails its a lucky dip it may wedge a bit of skirt under your con rod, may trash your bore and ruin it could have the entire top above gudgeon come clean off and do no damage to anything.. Cant say for sure.

B, c, and d sizes are in fact for used barrels with nikasil plating. Like the others said, u need to measure with a bore gauge. They make A-D size pistons for that exact reason. Sleeves can't be measured down that fine. That's why they're usually matched with .5mm incroment pistons. A-D pistons are measured in .01mm incroments for the nikasil cylinders.

don't know what sort of cylinder it is but if mitaka lasted that long in a kmx I'll just leave it until it loses power then since you were probably riding the same style that I do, when I do take it off I will give it to the shop guy to have him measure it then he can do the maths to see what I need, thanks for the replies