Correct Ring Position?

[roundhead]

I just tore apart an HT 101 4 mix pole saw. I need to reinstall the piston but I do not see any marks as to where to align the rings. Every other saw I have rebuilt had marks but this piston does not have any that I can find. Anyone know? Thanks

 

[redunshee]

without exhaust indicator on the piston crown,I would install piston with the ring pins toward the intake side of your pole saw. I presume this is what you asked.

 

[HarleyT]

 

[roundhead]

without exhaust indicator on the piston crown,I would install piston with the ring pins toward the intake side of your pole saw. I presume this is what you asked.

Yes thanks for clarifying that. I don't see any pins or anything so I will position them close to exhaust port

 

[roundhead]

View attachment 548977

Thanks. That helps me. There are two rings. Short piston.

 

[Sepia]

I assume a more knowledgeable poster will chime in here soon, but if there are no locating pins in the ring grooves, what keeps the rings from rotating during use and having the ends protrude into the ports and catching/breaking?

 

[67L36Driver]

[emoji849]

I always position ring end gaps at 180 degrees on four stroke cycle engines.

Piston has mark because of wrist pin offset toward direction of rotation. Reduces skirt load and piston 'slap'.

 

[hedge hog]

Its the same as any 4 stroke
All the breathing is above the piston
Two rings 180 degrees from the other


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[Sepia]

I assume a more knowledgeable poster will chime in here soon, but if there are no locating pins in the ring grooves, what keeps the rings from rotating during use and having the ends protrude into the ports and catching/breaking?

Okay now I see the error of my ways - it's a 4 stroke lol

 

[jr27236]

Yes four strokes just have their end gaps positioned opposite each other.
Why did you tear it down in the first place? Was there something broken in it?

 

[Sepia]

It's been a few years since I last built a V8, but back then I used to make sure the top ring had it's gap on the loaded side of the cylinder, second ring gap 180 degrees from the first. Some guys would put the gaps 90 degrees apart - both on the loaded side, and some guys would go to the trouble of pinning the rings in place.

 

[HarleyT]

Stihl says 120 degrees apart.

 

[HarleyT]

Doesn't matter much though.

 

[roundhead]

Yes four strokes just have their end gaps positioned opposite each other.
Why did you tear it down in the first place? Was there something broken in it?

yeah long story....I shouldnt have. i lost my compression tester awhile back. guy gave me the saw and said it had no compression. since the valves are on top of the piston, i couldnt look at the cylinder through the intake or exhaust. i wasnt thinking and then i realized that is is a "clamshell" so i took it apart to look at the cylinder. no scoring. i know it was dumb. i will go through it all. he said it was submerged and yeah there is alot of corrosion...may have been dunked in salt water IDK

 

[hedge hog]

That is not good!


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