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Pretty sure I remember reading somewhere that you can run a single piston ring.. my question is do you run the top one or bottom one. What are the advantages, disadvantages of this.. sorry if this has been covered..
 

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I would never put a single ring in a double ring groove piston...........The extra groove will lessen compression when left open............

The advantages are supposedly faster revs but I would rather lighten the flywheel,,add a boost bottle and rocket key ,, polish the piston and crossdrill the clutchpads before I remove an intricate part that helps seal the cylinder compression...........

The cheap cast rings cant really handle the job IMO...........If you can get chromolly rings and fill the groove in the piston with JB Weld it may work after a cylinder honing............
 

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I am going to take an engine that the rings have seated, and take it apart coat the rings, piston, rod and main bearings, pin, crank and clutch bearings, bake them in my oven for at 350 degrees for 1 hour, then re-assemble it. Its called Floroucote, you can add it to your engine oil, also.
Used it in my BMW 2002 Tii car, worked real good. We put it in a V drive unit in a boat w/ a 350 chevy V8. It was so noisy, after we added that Teflon it was like someone put ear plugs on it.
It is similar to Duralube2, but much better.
 

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Yea i'm not sure about single ring pistons, i remember them being all the rage when i had my Aprilia RS125, but when i look now all the decent manufacturers, Wiseco/Vertex/Pro-x/Wossner - seem to just offer two ring pistons, i think maybe for full on two stroke race bikes the difference maybe worth it, but when it comes to road bikes and indeed pocket bikes i think it's pretty pointless
 

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When I was looking at daves, saw a bunch of RC engine parts, they only had 1 ring on the pistons, on 30cc.
 

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the advantages of a single ring is less drag, less friction,less heat and less wear on the bore walls, down side is faster ring wear. never run a 2 ring piston with just one ring, as the open channel leaks pressure into the exhaust port.
 

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the advantages of a single ring is less drag, less friction,less heat and less wear on the bore walls, down side is faster ring wear. never run a 2 ring piston with just one ring, as the open channel leaks pressure into the exhaust port.
Especially true on the pressure comment.
I broke my piston ring when installing, and unless your using better built ring, if it asks for 2 rings, use to rings. I couldn't get mine to start using just one due to low compression. I installed a second ring after I ordered one, and it started right up. Modding is great but I think theres a million other things you can do to mod your bike for performance before attempting the unguaranteed one ring mod.
 

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If you look at the one ring pistons they are longer than a 2 ring.
 

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chung yang made a engine called the gp420. it is/was a 40cc scaled up G230rc. it has a 40mm bore 10mm wrist pin and a single thin 1mm piston ring. stock the motor revs to 16-18k when CY came out with the bigger 42mm bore 46cc GP46c they discontinued the 40mm bore. they are extremely rare in the go-ped scene but with luck i managed to find a complete 420 topend kit and a second spare piston and ring. if u can find a gp420 piston it will work in a small bore cag47 motor, ive tried it, and it works great. i didnt loose much compression and defiantly got more peak power and atleast 2k more rpms
 
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