scoot just kinda quit producing power

[vs7]

150cc gy6
On the last leg of a 15 mile ride my bike just started making loud popping sounds, which might sound like sputtering through a stock muffler. I lost power immediately. After pulling over to make sure my exhaust pipe wasn't broken I tried to accelerate, but almost instantly it was nothing but just popping and bogging.


About a month ago I was forced to ride home about 5 miles with no muffler(I kept it at 10 mph or so), as the stock one broke off. Every thing has seemed fine, except every time I check the exhaust valve there is no clearance, even though I always adjust it to .004". Could I have ruined the valve? Would that cause these symptoms? Is an exhaust valve difficult to replace?


Any advice will be greatly appreciated. Not looking forward to a 20 mile round trip bicycle ride to work tomorrow.

[Roscoe]

I'd be checking the fuel delivery system, and the ignition. A new spark plug might just fix your problem. The only reason I can think of as to why the exhaust valve won't hold it's setting is valve seat recession. I'd be checking compression before tearing into the engine. Check things like the big rubber intake manifold for cracks, fuel filter, clogged main jet, petcock operating as it should, gas tank venting. The popping sounds to me indicates an ignition problem or lean fuel mixture. If it is the exhaust valve or valve seat causing the problem I'd just get a new head assembly and change that out and then make sure the motor isn't running to lean and causing the motor to run to hot leading to early valve failure. Let us know what you find and how you fixed it.

[vs7]

Fixed. The clip on positive wire connecting to the ignition coil had snapped in half and was making a sporadic connection.


Thank you Roscoe, for the advice about getting a new head assembly. I'll be doing that next week.