one for the pros,returning to an old problem

Jason Luther /

i got a used cylinder and new piston for my riverside and had the cylinder bored out to .0015" clearance. after i rode around for a while it would seize, but i could immediatly start it back up although it would seize again in a short while (i stopped doing this once i figured out what it was doing). so i put the old piston/cylinder on, no more problems. then i realized that my fuel filter was almost completely clogged and gas was just dripping out. is it everyone opinion that it seized due to not enough clearance, or running way to lean? the manual isnt real specific on the clearance you need, and i think im right in there. can anyone shed any light? -jason

Re: one for the pros,returning to an old problem

Steve Murphy /

Did it seize or just stall? I'm guessing it was because of the fuel problem, though if it were that bad ya'd think it would still act up, at least a little, with the original cylinder and piston.

Re: one for the pros,returning to an old problem

Jason Luther /

no it definatly seized. but i changed the filter while i swapped piston/cylinders so i dont know for sure.-jason

Re: one for the pros,returning to an old problem

Xxxxxxx Xxxxxxx /

is there a difference in size between the old cylinder/piston and the new one? if not i don't think it's a matter of being to lean, i think it's clearance.

Re: one for the pros,returning to an old problem

I was thinking clearance issues too, jay.

But if he bored the cylinder 0.015 over, I would think that would take care of a binding piston.

Sounds like a really odd problem to me.

Re: one for the pros,returning to an old problem

Jason Luther /

yes, the new piston was the next size up,. so i had the cylinder bored .0015" over. the clearance of the piston im using now is about .0025", but the piston is in bad shape so i dont know how accurate it is. -jason

Re: one for the pros,returning to an old problem

Jason Luther /

also i could start it up again immediatly. so if it was too hot and swelled in there, it didnt even have two seconds to cool.

Re: one for the pros,returning to an old problem

Well, if your piston is .025 over you should have had the cylinder bored .025 over. Clearance for most engines is usually .002 to .005 inches.

Starving a 2 stroke for fuel will seize it, but it's not technically seized untill your piston melts and turns the whole thing into a paperweight.

When you are having something bored out, bring the piston with you to the machine shop and they can match everything exactly(meaning with the proper clearances).

Re: one for the pros,returning to an old problem

Well, he did say that the 'clearance' was 0.0025"

Jason - are you using the right notation on all these measurements you are giving us?

15 thousandths is 0.015, about the gap of most breaker points. (also about the thickness of a matchbook cover).

Re: one for the pros,returning to an old problem

Jason Luther /

.0015" one and a half thousanths. i didnt have the old piston, it was melted into the cylinder. the piston im using now is from a different engine, where the clearance is about .0025" two and half thousanths. ie honed out the problem cylinder to about .0025". so really i just want an opionion to if its too tight, or should i go ahead and order rings and use the bored out cylinder and piston?-jason

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