Compression

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I've noticed in some threads about compression. I'm curious on how compression is checked on these small engines? Mine is the 2.5 and think I may have burned it up during the crash a few weeks ago. Although after the crash, it did run long enough to run the tank dry.

 

[olds97_lss]

If you can easily roll the engine over top dead center when cold by using one finger to roll the flywheel, it's probably dead.

A sure way to tell is to pull the engine apart and see how far the piston goes up through the sleeve. If it easily goes far enough to stick out the top of the sleeve, it's dead. If all internals are good, it can be repaired by having someone pinch it.

You can see what I'm talking about here in the first post. I put photo's of the "before". You can see the pistons sticking out the top of the sleeve:
https://www.rcnitrotalk.com/forum/showthread.php?t=56420

The two really bad ones are the SH28 and Dynamite Mach 427.

 

[brad55102]

keep in mind a pinch only last for a short time, it's not as good as buying a new piston and sleeve. Also keep in mind that you have the Traxxas 2.5,,,,, so you can either buy a new piston and sleeve for $40 or trade your 2.5 in for a 2.5r for $80 or upgrade to the 3.3 for $110. (IMO this is the best thing to do(Upgrade to the 3.3)) But, you can buy a pinching tool for $15 on ebay or have someone pinch it for you, probably $30. Personally i dont recommend pinching.

 

[olds97_lss]

keep in mind a pinch only last for a short time

Have you had it done? I've had it done on many engines and the longest running one so far has 4 gallons through it after the pinch. Not an expensive engine either, OS21RG. The others are still running strong as well. I have more than a gallon through the XTM24.7 and Mach427 I had done the last time.