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Author Topic: M90 piston o-ring upgrade?  (Read 91 times)

ShadetreeMotorcycle

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M90 piston o-ring upgrade?
« on: October 29, 2020, 08:10:16 am »
Hello, I am impatiently waiting for my engine to arrive...I have Many upgrades planned....has anyone tried a Teflon o-ring on the piston? It seems like it would reduce drag and also be heat resistant...I admit I do not know what the green o-ring is made from...if I knew the size, I would get some Teflon o-rings on order....I do not mind being the one to test drive...

Adirondack Jack

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Re: M90 piston o-ring upgrade?
« Reply #1 on: October 29, 2020, 10:35:45 am »
The green o ring is made from fluorine rubber. It is misnamed by the engine folks, but that’s what it is. It is commonly used in aircraft and food processing machinery, and withstands petroleum and stresses well. These engines were initially shipped with two piston rings early on, which proved to work too well, no oil getting between them. They’re now shipped with one, and reports are of much improved life, as long as even a little marvel mystery or other suitable oil is used.

ShadetreeMotorcycle

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Re: M90 piston o-ring upgrade?
« Reply #2 on: October 29, 2020, 11:17:21 am »
Thank you for the info on the stock o-ring....I feel that trying a Teflon o-ring is pretty low risk, as if I don't like it I can always go back to stock....I am shooting for the ultimate in slow-run or fewest hits per minute. Thanks!

RedRyder

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Re: M90 piston o-ring upgrade?
« Reply #3 on: October 29, 2020, 02:15:01 pm »
You might not find a difference between a teflon or properly fitted rubber o-ring.
The correct o-ring size is 22 x 1 mm. It should fit a bit the ring groove should be a hair bigger than the 1 mm o-ring thickness.

This way when it fires, the pressurized gases push the o-ring down and get behind it in the groove and force it out to firmly seal at the cylinder wall.
When it is free wheeling the o-ring retracts a bit and has near zero friction in this state.

After your experiment, please let us know if teflon can do any better than that.

Most of all...... have fun...!!!

Gil



ShadetreeMotorcycle

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Re: M90 piston o-ring upgrade?
« Reply #4 on: October 29, 2020, 05:55:50 pm »
Thanks Redrider.....I am Greatful for the size info!...I am not so sure the teflon o-rings can do all the things you spoke of in your post....they are quite rigid and may not perform as well, but I have 14 pcs coming in the mail, to get free shipping so if they DO work, I may be able to share a few samples at low cost...I am not Counting on them working to be happy, for me the journey is more than half the fun and I love to tinker and experiment....I will share my findings if I have any positive results....its so nice to have fellow hobbyist to share ideas with, I specially enjoy videos of the engines running and what was done to achieve the results.

RedRyder

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Re: M90 piston o-ring upgrade?
« Reply #5 on: October 29, 2020, 06:28:17 pm »
I agree! It is the journey, the research, the experimenting, all the testing.... That where the fun is.

And of course with the older toys.... tracking down and digging up the history and preserving it for the future is another great pleasure in our hobby.

 

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