Hua Sheng lost power after engine came to a sudden stop

[abikerider]

Hi,
I am looking for answers to a problem with my Hua Sheng. I have it paired with a firebelly transmission. When I first installed it the idle was pretty smooth and the bike topped out at 35 mph on the flats. There were some initial issues with the firebelly transmission which caused it to break it's primary chain a few times. That issue has been resolved with better sprockets. The problem with the engine occurred the last time the transmission's primary chain broke and jammed, and caused the engine to stop abruptly. Now it seems to have less power, idles roughly and only makes it to 28 mph. I have since replaced the spark plug, adjusted the valves, inspected the carburetor, and changed the oil but with little improvement. There is also a new buzzing vibration that occurs around 21 mph which I don't remember being there before. My question is, what could cause this sudden drop in performance? Could the cam gears have skipped a tooth and changed the cam timing? Could the crank have gotten twisted and caused a shift in the cam timing while also causing the new vibration? Any other ideas?

Also, is there a service manual available in case I want to start disassembling the engine for a closer look? Maybe I should just buy a new engine? Any advice is appreciated. Thanks.

 

[Deleted member 8310]

Tough break, no pun intended. Sounds like something very serious has
happened internally with the engine.

If it were me I'd crack the case open and look inside. Also sure a local
Honda mechanic would know about proper timing and such.

Let us know what you find.

If you keep riding it there could be permanent damage.

Also there's an exploded view of your engine on bicycle-engines.com as well
as every part you'd need.

 

[abikerider]

With the help of GearNut on the other forum I found that the key for my flywheel had sheared causing the ignition timing to be way off. Luckily it was just a 50 cent part at the local hardware store so it was a relatively easy fix. I hope this helps other with this problem in the future.

Tough break, no pun intended. Sounds like something very serious has
happened internally with the engine.

If it were me I'd crack the case open and look inside. Also sure a local
Honda mechanic would know about proper timing and such.

Let us know what you find.

If you keep riding it there could be permanent damage.

Also there's an exploded view of your engine on bicycle-engines.com as well
as every part you'd need.

 

[arceeguy]

I agree, the flywheel key is probably partially sheared and upsetting the ignition timing.

I don't know about the huashengs, but I've seen several small engines of various makes where the key was part of the flywheel, so if it sheared off, the flywheel would need replacement.

 

[Deleted member 8310]

loosing my top end power

Have an exploded view drawing of HS motor but not seeing anything that looks like a flywheel nor are any parts labled as such. Where exactly is it?

Does it double as the fan on the pull start side?

 

[Deleted member 8310]

I found the answer mine wasn't sheared.