80cc loosing power at top speed

[Edenfrench57]

My 80cc is losing power at top speed and feels like it’s bogging down and isn’t holding speed please help

 

[Greg58]

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.

 

[Edenfrench57]

It tops out at 46kmh and That’s wide open

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.

 

[Greg58]

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.

 

[Edenfrench57]

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

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.

 

[Greg58]

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.

 

[Edenfrench57]

3/4 it holds its power more
I’m also running 32/1 ratio but I’ve been using outboard 2 stroke oil

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.

 

[Greg58]

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.

 

[Edenfrench57]

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?

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.

 

[Greg58]

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.