Piston Rings

[dougsr.874]

How much space should there be between the ends of rings on a 50cc two stroke.... I bought a new piston with the rings on it and the space between the ring end is about half to three quarters of an inch apart....so when I put it in the cylinder the ring ends are hitting a port and seizing the engine...Also, is there a front and back to a new piston in a new cylinder....Any comments are appreciated....

 

[Al.Fisherman]

How much space should there be between the ends of rings on a 50cc two stroke.... I bought a new piston with the rings on it and the space between the ring end is about half to three quarters of an inch apart....so when I put it in the cylinder the ring ends are hitting a port and seizing the engine...Also, is there a front and back to a new piston in a new cylinder....Any comments are appreciated....

Only a few thousands of a inch. Pistons?
I have a post about the piston, let's see if I can find it.

Looking at the cylinder, from the rear (intake port facing you). You should see both piston ring pins. Top pin to your left and bottom pin to the right.




I find this the easiest way to insert a piston in these HT's. Others will tell you differently.

With the cylinder off, lay cylinder head down on a work area. Line up the rings on the piston grove with the pins. Insert the piston from the bottom of the cylinder. Compress top ring and slide in, then the bottom ring the same way. The cut outs on the cylinder lets you hold the rings with your thumb and forefinger. Lightly tap in. The bottom of the cylinder is beveled and guides the piston in. Take cylinder and piston and insert the rod, make sure the wrist pin clip is installed.

 

[dougsr.874]

Mr. Fisherman, Many thanks for your info...obviously, the rings were broken when I bought the piston....

 

[FelipeCobu]

I was wondering... What will happen if I run the engine with only one piston ring? Do someone tried this?

 

[Greg58]

If the engine runs it wont be good, not enough sealing with one ring. Low compression means low power.

 

[Skyliner70cc]

In 2006, I purchased a new HT engine from a recognized and respected vendor here that ran poorly. Upon teardown, I discovered that it had only one piston ring. A new ring fixed that problem and engine is still in use today.

 

[Lunardog]

If Im not mistaken there should be an arrow on the top of the piston that should point to the exhaust port.

 

[Greg58]

My bgf 48cc does not have any markings on the piston, so I left the right clip in the piston and pushed the pin out with a small punch.