Advice on Poulan PP335 re-Ring (38mm piston)

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1929Heisman

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Mar 18, 2021
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Location
Roswell, GA
Hello Folks,
I've been pulling great info and advice off this site for years. Here's one where I need some tailored advice.

I have a PP335 trimmer for household use (pole saw and hedge trimming only) that I took to a shop because I just wanted it fixed. I had fuel backflow and carb issues after I rebuilt carb and still no start and leaks. Frankly, I didn't want to deal with it just told them to fix it. (I'm not new to rebuilding/fixing Chainsaws/lawnmowers and rebuilding truck transmissions--I"m just getting old and I just rehabbed my Briggs lawnmower eng & carb). They said the trimmer compression came back at 56psi and wasn't worth fixing. Typically I agree, but I do not belive their low psi reading...at least not that low. I always tune my carbs rich, open the mufflers and run richer mixture. My inspection after I got home and broke it down showed no gouges /scratches on internal cylinder or piston. Moderate build-up of carbon on piston top and exhaust port. Engine does not have a lot of hours. This is a strato engine/carb set up. (Also, the jug had the Husky emblem on it and a 3524 part indicator..go figure. Interchangeable).

So, using my dial calipers, I got:
A) Piston: measured 36.855mm above the ring and 37mm below the ring (adjusted to metric--variances could be off a bit as I was holding all parts by hand--not fixed surface)
Is it usual that a piston would have a slightly tapered top above the ring than below? Also, any benefits to changing the piston to plated?
B.) Ring: .054" and .052" depth; .046" thick--What are the usual specs when new?
C.) Gasket seals looked in good shape (but flimsy design). I'd rather use permatex.

1. Do you think a new piston ring is enough? Also what is the typical depth (protusion) of the 38MM ring? [to determine wear]​
2. I heard the piston rings for the 41.1mm piston fit these...is that true? If so, does it provide better seal/compression?​
3. Thoughts on a good, inexpensive compression tester for small engines as it appears many rarely work right or are inaccurate.​
Thanks in advance for your comments. Yes, I wish I had a Stihl, but I don't. I appreciate the warriors against throw-away-culture​
 
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