From:David e-mail:dklein61-A-gmail.com
Subject:RE: RE: RE: RE: RE: engine locks down and refires Date:Tue Jun 9 19:34:03 2015
Response to:20543
I know very little about 2 stokes. So I'll look into the
clearance. I have a shop close by I can get him to check
it.
Thanks and appreciate the info.

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That's usually the case when the clearances are
borderline. Two stroke motors, because they have oil in
the fuel, are set up to tighter clearances than their
four-stroke cousins. Aluminum expands and contracts at a
faster rate than cast iron does so it's the piston
expanding in the bore under high heat conditions that's
locking it up. Racers open up the bore above tolerances
for those conditions and when the motor is cold you can
hear the piston slap when they first start up. I'm sure
there are more experienced people here on the Exchange so
if they chime in on this listen then make up your own
mind as to which direction you want to go. Either way....
Best of Luck!

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BOb, so would the piston free up instantly or would it
take time?

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Thanks I'll check it out.

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Let's assume you don't have a big piece of cardboard
blocking the airflow over the engine or a lot of broken
fins. Your bore to piston is too tight and it locks when
the piston expands in the cylinder. Take it and have the
cylinder honed(not bored)another .001" to .0015" (that's
a thousandth or thousand and a half inch oversize). The
easiest way to tell a 125 from a 165 is if the spark plug
is set at an angle it's a 125. If it stands straight up
it's a 165. You said 50+ miles an hour? Probably a 165.

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New here and with the hummer. I have a 59 and when I
ride for a few miles at 50+ mph it will lock down and
slide the rear tire. I can immediately pull the clutch in
and kick it and fires right back up. If I ride at lower
speeds it runs fine with no trouble. Any ideals? I run
the 25:1 oil mixture. As I read thru the site it looks
like years of experience here. I have already used a lot
of info from this site to get it running. Thanks to all
!! Also, how do I know if it's a 125 or 165 motor.

Thanks for everything guys
David