80cc loosing power at top speed

Welcome to the forum, it can be a number of things that cause the engine to lose power. One easy test is to remove the air cleaner and do a run, if it runs better you need a smaller jet, if it runs worse you need a larger jet. At what speed and rpm is it topping out? The ignition doesn't have a advance so it limits timing.
 
It tops out at 46kmh and That’s wide open
Greg58 said:
Welcome to the forum, it can be a number of things that cause the engine to lose power. One easy test is to remove the air cleaner and do a run, if it runs better you need a smaller jet, if it runs worse you need a larger jet. At what speed and rpm is it topping out? The ignition doesn't have a advance so it limits timing.
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Will it increase speed if you back off the throttle some? Wide open throttle is regulated by the main jet, when you get a chance try the tests to see what helps. On a new engine your speed is not bad, after break in it should get better. Oil to gas ratio can hurt performance too, I run 24/1 for break in then after a couple of tanks I switch to 32/1.
 
It goes wide open and hold its for maybe 50 to 100 metres and then starts loosing power and then when I back off for abit and then go wide open again it picks up power and does the same thing
Greg58 said:
Will it increase speed if you back off the throttle some? Wide open throttle is regulated by the main jet, when you get a chance try the tests to see what helps. On a new engine your speed is not bad, after break in it should get better. Oil to gas ratio can hurt performance too, I run 24/1 for break in then after a couple of tanks I switch to 32/1.
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Like I said try 3/4 throttle and see how it runs, how much have you run it? If it's new I would ride it till it's broken in.
 
You need a smaller jet or to open up the exhaust, reducing the back pressure on the muffler will help too, a two cycle relies on muffler back pressure to perform. It's a balancing act that takes awhile to get right.
 
the exhaust has a leak where the gasket is and there is no gasket the exhaust was striagjt piped for a day because it snapped off but I welded it back on and it’s working quite well but it does have a leak could that be an issue and do you mean the cap at the bottom of the muffler?
Greg58 said:
You need a smaller jet or to open up the exhaust, reducing the back pressure on the muffler will help too, a two cycle relies on muffler back pressure to perform. It's a balancing act that takes awhile to get right.
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make sure the pipe seals good, also add a mount near the end of the exhaust to support it to keep it from breaking again. A good expansion chamber will help, it takes trial and error to see what works on yours.
 
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