Engine Trouble cant get full power?

[pedropete91]

hey there i have an 80cc motored bike and when im trying to get top speed it wont let me ping it?. It bogs down on full throttle? so u got to hold it just before flat to sort of build up speed?.

-A80 (chrome)
-speed carby
-36t sprocket
-premium unleaded 98
-s.b.p expansion chamber
-26" southern star

 

[Fabian]

The words "Chinese bicycle engine" and "full power" are a paradoxical oxymoron. They should not exist in the same sentence.

 

[Fabian]

Be happy with the power that you have, because more power is inversely proportional to how much time is spent trying to tinker with the system.

 

[Ludwig II]

How to make a small fortune out of tuning 2 stroke engines:

Start with a large fortune.

 

[Lunardog]

Too funny.....too true, but too funny.

 

[FelipeCobu]

If I do understood it well: At 3/4 throttle it runs nice, full throttle it starts to fail. Looks like you have a small jet in your carb. What carb? What fuel/oil ratio? What needle position are you running?

Felipe

 

[adrian101]

If I do understood it well: At 3/4 throttle it runs nice, full throttle it starts to fail. Looks like you have a small jet in your carb. What carb? What fuel/oil ratio? What needle position are you running?

Felipe

If you answers these question i can give you the right solution to your problem also how far is your idle screw in on your speed carb.

 

[motorpsycho]

the main jet is too lean (too small)....causing it to bog at w.o.t.
also, get rid of the 98 octane fuel and run the cheap 87 octane struff.
high octane fuel is a waste of money in one of these engines, because they are low compression.
it will run better on lower octane.
what fuel - oil ratio are you running, and what oil are you using?

the needle position in the carb has nothing to do with full throttle.
the jet needle is only in effect from idle until about 3/4 throttle.
after 3/4 throttle, the needle is completely out of the main jet well, and the only thing doing the fuel metering at full throttle is the main jet.
changing the position of the needle to fix a full throttle bog is useless.

 

[fm2200]

I recently had the same thing, the way to check if your getting less fuel to the carb due to the fuel inlet that the fuel line slips over. First thing to do is remove the screw on the side of the bowl on your carb. After removing the screw you should get fuel spilling out. Once the bowl is empty then the fuel should be coming out if everything is good. If there is a very small trickle only or only drops then your brass fuel inlet is the problem. Remove the brass fuel inlet and clean it with a small diameter wire. This should make your problem disappear.

 

[pedropete91]

cheers for the advice people. All i wanna do is be able to beat my mate who has a f80 stock nt carby and a 40t i dunno why mines slower it shouldnt be. Yes 3/4 is fine but full throttle it bogs down (speed carby stock jet)(200ml/5L fuel)(needle position is 2nd to top) only just changed it thought it was running abit better.(shell premium unleaded 98 high octane)(idle screw is about 2 or 3 turns in)(valvoline oil)