universal piston/cylinder clearance ?

[jaguar]

I'd like to know if all other 2 stroke dual purpose bikes close to 200cc would go by just about the same piston/cylinder clearance that the KDX200 goes by.
My friend has a DT200 and he showed me the resleeved cylinder and new piston and I swear theres just about zero clearance which isn't right but I need to know, for arguments sake when I go talk to the guy who sleeved it, if more or less the same clearance (close to .08mm) would apply.
I swear, the piston stays where its put in the cylinder when upright on the work bench! It should slide down shouldn't it? (if there's enough clearance).

 

[davis]

Are the rings on the piston? If they are not it is too close. A easy way to check clearence is to stick a feeler gauge between the skirt of the piston and cylinder wall. You should be able to stick .0015 between the two. Check with the maker of the piston they set the clearence. Some have a greater amount.

 

[davis]

Sorry .0015 of a inch clearence

 

[jaguar]

No, it's without the rings!!
I talked to the machinist today. He said that for the off-brand replacement pistons sold down here he leaves half as much clearance. He said these pistons flare out more at the skirt than factory (or good replacement) pistons. But why he thought that required less space was not told to me. (limited communication since my spanish isn't that great). I'd like to see him measure a factory and non-factory piston while I'm watching to make sure it isn't some half-witted story. If true then maybe the skirts wear down to a normal width quickly enough which would bring the tightest clearance back to normal. Maybe

 

[davis]

All pistons are bigger at the skirt that at the top of the piston. I have seen pistons setup so the piston can only enter from the bottom and not come out the top of the cylinder. It matters what the mfg. of the piston recommends for clearence. Some are .015, .002 and .0025 of a inch. When you run the engine for the first time add extra oil in the mixture. Don't over rev or ride hard. Give the piston a chance to break in.

 

[jaguar]

Well this one can exit at the top of the cylinder so maybe it will live.
Yeah I just told my buddy to not give it full throttle for the first week of riding if he rides it every day. I think the bike has an oil injector which I'm not a fan of since mine died and seized the piston. I like to know what is going into the engine (how much oil in this case).
thanks for your input

 

[BRush]

davis is right. Follow the piston mfgr's recommendation. Different types of pistons (cast or forged) require different clearances. My Wiseco piston came with a sheet which gave the required clearance based on piston diameter and cylinder type (plated or cast iron).