49cc piston

[Hashbrown]

I know that there are two different size pistons, is that only for 66/80cc or does the 49cc have two differant sizes? I just bought a reed valve and wanted a windowed piston (or modify one) but everywhere ive looked they don’t specify if it is a 40mm or 38mm.
The place where i bought my kit from says its a 38mm stroke

 

[crassius]

I haven't seen every possible configuration of these motors, but I doubt there is a 40mm stroke on any of the small motors. Knowing the size of your piston, you could measure distance from skirt to wristpin hole on a pic at site you are ordering from and see if it is same as measurement on your actual piston.

 

[Hashbrown]

I haven't seen every possible configuration of these motors, but I doubt there is a 40mm stroke on any of the small motors. Knowing the size of your piston, you could measure distance from skirt to wristpin hole on a pic at site you are ordering from and see if it is same as measurement on your actual piston.

Now can i use the reed valve without a windowed piston, Or will it just run like crap?

 

[crassius]

most folks seem to get best result with cutting windows - probably works that way for any reed setup, but a reed user would know more

 

[Hashbrown]

So zeda made 2 youtube videos using bolt on reed valves. They put the motor on a dyno, they first tried it with just the reed valve and it cut the hp by more than half then they tried it again but added a windowed piston and it barely made 1hp.
So it looks like the bolt-ons aren’t worth the money.

 

[MotorBicycleRacing]

I know that there are two different size pistons, is that only for 66/80cc or does the 49cc have two differant sizes? I just bought a reed valve and wanted a windowed piston (or modify one) but everywhere ive looked they don’t specify if it is a 40mm or 38mm.
The place where i bought my kit from says its a 38mm stroke

A 48 cc piston is 40 mm OD and inly comes in 38 mm stroke.
Some 48 cc pistons have a flat top and others have a dome which are the only differences I know of.
What kind of reed valve?

 

[crassius]

not sure if he meant one extra hp or just one total hp

 

[MotorBicycleRacing]

hey put the motor on a dyno, they first tried it with just the reed valve and it cut the hp by more than half then they tried it again but added a windowed piston and it barely made 1hp.
So it looks like the bolt-ons aren’t worth the money.

Making 1 extra HP on a 2 HP motor is HUUGGE.

 

[Hashbrown]

Sorry if i wasnt clear I meant that the 2hp motor lost 1hp in both tests.
It was with the RSE reed valve.

 

[Hashbrown]

I wonder if the rse reed valve is too short to work properly.

 

[crassius]

there was one report of reeds too stiff to fully open, but not sure if that was a flaw or true for all