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how to check if pinch is good on an engine?

how to check if pinch is good on an engine?

Old 05-28-2008, 08:04 PM
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Originally Posted by slaytanic
Do the flop test. Hold onto the flywheeland let the weight of the engine fall to the side. If the compression is enough it will not flop over, or turn over. It will stick and hold the weight of the engine.
As for a used engine, how long it should not flop over? For 5 second? After 5 second flop down mean still ok? Please advise. thanks.
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Old 05-28-2008, 09:14 PM
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you cant only judge by the engine at room temp, it might feel like it has life, but once it runs for a little bit, it may die once everything heats and expands. my buddy had an old losi mach427 that would start fine...run for a few minutes then it would die and not start up again
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Old 05-28-2008, 09:42 PM
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Originally Posted by rdub202
my buddy had an old losi mach427 that would start fine...run for a few minutes then it would die and not start up again
I know the feeling, that's usually my first sign that the sleeve is going. I'm no metallurgist, but it seems like the ABC sleeves in these things expand more than the aluminum pistons with heat. So yeah, an engine might start fine (in fact, it'll probably start easier than it ever has before), but once it gets up around running temperature it's like someone went and backed out the idle screw 3 turns. A tiny gap forms between the piston & sleeve, and the pressure from combustion finds it's way into the bottom end (a condition called "blow-by"). For all I know, because these are 2-strokes that might even be enough to start igniting the air/fuel mix waiting in the bottom end.

There are places like RayARacing that'll do a sleeve resizing for less than it'd cost to buy a new set. Basically just send the guy your piston & sleeve and he'll place the sleeve in a fixture that kinda "crushes" the pinch back in.
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Old 05-28-2008, 10:03 PM
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we knew it was an old motor, we werent expecting anything out of it.

and yes, there are a few repinching people/places out there
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Old 05-10-2012, 01:17 PM
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I just got myself a Ray A Racing pinching machine, i`m looking for some video footage of the hole process, is anyone aware of any ??
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Old 05-10-2012, 03:35 PM
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Originally Posted by Andrew_67
I just got myself a Ray A Racing pinching machine, i`m looking for some video footage of the hole process, is anyone aware of any ??
Did you asked Ray he will help
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Old 05-10-2012, 06:21 PM
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Just read and watch Rays web site,it tells you alot information if you understand these engines..

Last edited by nothin special; 05-10-2012 at 06:24 PM. Reason: add a word
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