hey all. posted about this on the scooter forums, and only got generalized answers. things i have already put on the list of things to check. looking for some new ideas so i can be sure and have a through diagnosis.


ive got a 80cc (formerly 50cc) chinese scooter, honda gy6 copy. recently i have noticed at around 8500rpm (rev limit is 9k) it will act like its loosing spark. no power, and you hear the intake, not the exhaust. (similar to an engine brake sound) it will do this till the rpms drop roughly 200rpm or so, then it will catch again. its been getting progressively worse the more i ride it. used to, it would bury the 50mph needle. now i am lucky to get to 45 in between all the cutting out.


my thought is check the spark plug, and the timing. i have the timing specs and valve lash, so i will do that tomorrow. scoot is running a #95 main jet, so i am fairly certain its not starving for fuel.

any ideas or brainstorming is much appreciated! (already checked for loose wires, we're good on that front!)

thanks guys.

How does the spark plug look..and how is the wire?
I had my bike act a little weird and it was one of the coils that was fubar.
Got engine compressions specs/ gauge?

if what art said checks out, seems like you might be floating the valve springs, did you put a cam in it?

stock cam, just a bigger jug. and the new jug is so high compression, i actually had to make a diy crankcase expansion chamber via the dipstick hole so the starter could crank it over.

after tearing into it today, and checking the valves, timing, and plug (which was slightly on the black side actually), i think i found the problem. the past few tanks of gas, ive been burning what was left of the 2 stroke gas from my snowblower. (50:1 mix) looked up the tailpipe with a flashlight and lo-and-behold there was fiberglass matte in there! i cant take the muffler apart, because i dont have any way to re- weld it, so i cut a few slits with the grinder near the end of the pipe. went for a short 5 mile ride, and not a single chug and it buried the needle again no problems.

my theory is that the matte absorbed the oil from the 2 stroke gas and caused a potato in the tailpipe type situation.

ill post back if i have any other issues, or if they return.


here is a video i took with the exhaust off. too bad i couldnt leave it off. sounded awesome. haha

https://www.facebook.com/photo.php?v...53516074897682

thanks alot guys!

two strokes hate old gas more than any other thing, the jets in the carb are tiny and get caked up super easy and the plugs seem to foul out alot. i always use new gas and only make what i am gong to use

Ya x2 as above^
I use to use Stabil ethanol treatment in my 2 strokes, to help keep the jets clean.
Plugs, always had some emery cloth handy to keep em clean & check gaps too.

well, scoot is a 4 stroke. figured the 2T gas couldnt hurt..... guess i was wrong!

guess ill be burning off the rest of the gas in the mower.