Please Help with piston rings

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sergman89

New Member
Jul 7, 2012
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I keep breaking my piston rings unfortunately.

what size are the piston rings so I can find a store i can drive to. Maybe you know a store? Napa said they don't have one so small.

How much would a small engine repair place charge to put 2 rings on?

I had to pause working on my bike last year and wish I handled this sooner because I need the bike to work yesterday:-||
 
YesImLDS

YesImLDS

Member
Jun 29, 2013
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Columbia, Missouri
It depends what size motor you have. You just have to take it really easy when putting them on. Start on one end and work your way around the ring on the piston til it drops in place if you have a 2 stroke (that's all I have experience with) If you have a 2 stroke motor you can easily find parts on ebay for really cheap. You probably won't find them in an auto parts store. I have a couple sets that I keep for spares, but I know you can find them online very easily if you have a common bike motor kit engine.

The size of piston rings for the stock 66cc/80cc 2 stroke are 47mm
 
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sergman89

New Member
Jul 7, 2012
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I got the basic version as far as I know and its an 80cc. I dont have the measurement tool so I am not 100% on the size.

Would it be a difference if it was 46mm?
 
YesImLDS

YesImLDS

Member
Jun 29, 2013
960
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Columbia, Missouri
If it says it's for the 80cc motor 9/10 times it's the right piston ring on Ebay at least. I believe the rings are 46mm for the 47mm piston because of the ring sitting on the piston itself.
 
Davezilla

Davezilla

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Mar 15, 2014
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Are you making sure the end gap is over the small pins in the ring grooves when installing the rings? if you're breaking the rings when trying to get the cylinder, this is the problem.
If they're breaking while trying to get the rings onto the piston, try putting the bottom ring onto the top, then slide it off the top groove and gently work it onto the bottom groove, I hadn't broke any rings installing them onto the piston but I did break one when one of the rings moved over the pin in the ring groove, I didn't notice it and when I went to slide the cylinder down over the piston it snapped the ring before I even realized there was a problem.
I also keep a few sets of spare rings on hand when I'm putting an engine together just in case, but it does get easy once you get used to holding them in place while installing the cylinder.
 
Davezilla

Davezilla

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Mar 15, 2014
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San Antonio Texas
yup... and the ring has to be right side up or the slots in the ring will interfear with the pins... Your drawing shows the rings upside down too because the slots in the rings are for there to clear the pins.
I've heard of a few people either being unable to get the piston into the cylinder or breaking a set because they didn't know the rings could be installed upside down so that's another thing to watch for when putting an engine together.
 
mapbike

mapbike

Well-Known Member
Mar 14, 2010
5,502
109
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Central Area of Texas
Actually the rings in the pic are right, the pins in reality will be on the upper part of the ring groove in the piston, but yes Dave made an excellent point.

A person has to be one who understands these tings and pays attention to detail or these little things will eat their lunch.
 
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NebraskaJeff

New Member
Jul 17, 2022
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sergman89 said:
I keep breaking my piston rings unfortunately.

what size are the piston rings so I can find a store i can drive to. Maybe you know a store? Napa said they don't have one so small.

How much would a small engine repair place charge to put 2 rings on?

I had to pause working on my bike last year and wish I handled this sooner because I need the bike to work yesterday:-||
Click to expand...
What size is the engine itself if it's the 80cc/66cc engine the rings should read about 47mm if it's like mine they are honed out to 49.02mm which the rings are 50.01mm
 
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NebraskaJeff

New Member
Jul 17, 2022
3
0
1
51
sergman89 said:
I keep breaking my piston rings unfortunately.

what size are the piston rings so I can find a store i can drive to. Maybe you know a store? Napa said they don't have one so small.

How much would a small engine repair place charge to put 2 rings on?

I had to pause working on my bike last year and wish I handled this sooner because I need the bike to work yesterday:-||
Click to expand...
 
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