Power cutting off at high rpm

Datboi

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I have a 2 stroke 80cc stock chinese engine. I removed the muffler cap and power increased greatly, it revs up much faster and has a lot more power.

However at full throttle when it reaches a certain point it starts cutting out very fast.
Like imagine losing power several times a second, that's the best way i can describe it.

It runs it just doesn't make any more power at that point.

Im thinking the main jet is lean?

Also, i know 2 strokes dont like running with a "straight" pipe as they need back pressure

Since the stop pipe runs like s**t with the cap on, i do have a exhaust pipe from a 2stroke scooter i think, i would need to do a few mods to fit it, do you guys think it would be a good idea?

What moda do you recommend for these kits?

I only ride off road mind you!
 

Sidewinder Jerry

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There are tweaks that increase power some on any engine. With all engines they have a certain rpm where max horsepower is reached and an rpm where max torque is reached. Going beyond these rpms won't increase either hp or tq.
 

Datboi

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There are tweaks that increase power some on any engine. With all engines they have a certain rpm where max horsepower is reached and an rpm where max torque is reached. Going beyond these rpms won't increase either hp or tq.
Yeah but is my main jet lean? Im not sure if that's a sign of being lean or what, it doesn't do it with the cap on
 

Sidewinder Jerry

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When tuning a carburetor use a tachometer then you'll know exactly what affect your adjustments are having. A tale tale sign you're to lean is the engine doesn't run as well with the choke fully open.
 

Datboi

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Is it sputtering at full throttle or just losing power. Try hitting a steep hill at full throttle, does it kick back up and make power?
On a steep hill it'll go no problems, it just seems like when its close to topping out it starts doing that and stops making power.



With the cap of the muffler on i have much less power across all rev ranges, but higher top speed and once it reaches top speed it doesn't do that"cutting out" it does with the cap off...
 

Chainlube

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On a steep hill it'll go no problems, it just seems like when its close to topping out it starts doing that and stops making power.



With the cap of the muffler on i have much less power across all rev ranges, but higher top speed and once it reaches top speed it doesn't do that"cutting out" it does with the cap off...
Cut the bottom off a soda can and hose clamp it on to your muffler with the pour spout down, should add just enough back pressure. With the cap off it will loose pressure and won't load the cylinder.
 

Datboi

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Cut the bottom off a soda can and hose clamp it on to your muffler with the pour spout down, should add just enough back pressure. With the cap off it will loose pressure and won't load the cylinder.
Wouldn't that be the equivalent of putting back the cap?
 
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