HuaSheng 142F Problem, Need Advice

[SpoopyToof]

I've got a HuaSheng 142F 4 Stroke with a 44t sprocket, 26 inch wheel and an NGK plug. The rest of the engine is stock and no real modifications have been made to it.

This has been an issue since the day I got the bike, 6 months ago. The bike takes off great and hits 19-20 mph with no issue at all. It's torque is perfect but when I reach my 20mph, I'm at about 1/2 throttle. If I try to go any higher on the throttle, it'll feels like it chokes up. In other words, it refuses to redline. I've seen these bikes do 25 mph easily with no changes, so something is wrong.

The bike doesn't die out or anything if I exceed that 1/2 throttle, it just sort of chops forward, chokes, and drops me back down to 20, If I try to hold it, i'll feel an occasional jerk forward but it'll always cut back down to a rough 20.

Things I have done

Valve Adjustment
Cleaned the Carb
Tried 89 and 91 octane gas
Checked Carb Gaskets
Cleaned Spark Plug
Upgraded Spark Plug (NGK)
Cleaned the Air Filter (and removed for testing)
Checked Clutch Pads and Clutch Assembly (It's fine)
New Fuel Filter
Cleaned Float Bowl

Things I haven't done, but might try

Upgrade Exhaust Pipe
Upgrade the Carb / Intake
Try a new CDI / Magneto Rotor
Drill my Jet

Keep in mind, I'm not trying to performance mod this bike yet, I'm just trying to get power that should already be there. I know a good pipe or a good carb might help, but I think this is an issue, not a performance tweak.

I read another thread about the CDI limiting RPM's, but I have the non limited CDI in the engine, I checked. In the same thread he mentioned changing his Magneto rotor, but I'm not sure I wanna buy one simply for diagnostics.

Appreciate any advice. Thanks.

 

[MotorBicycleRacing]

When you mention your specs the gearbox is important.
You have the one of the worst, a pocketbike chain box.
Even your pic is hiding it like the dishonest sellers do. Bashful gearbox syndrome!

The stock carbs can be problematical.
Does your mixture screw have a brass plug covering it?

Did you clean the idle jet?

Best to get an NT or Speed carb to replace the original.
You will need a new manifold too.

Redline on the HS is 7800 rpm.

This has been an issue since the day I got the bike, 6 months ago. The bike takes off great and hits 19-20 mph with no issue at all. It's torque is perfect but when I reach my 20mph, I'm at about 1/2 throttle. If I try to go any higher on the throttle, it'll feels like it chokes up. In other words, it refuses to redline. I've seen these bikes do 25 mph easily with no changes, so something is wrong.

The bike doesn't die out or anything if I exceed that 1/2 throttle, it just sort of chops forward, chokes, and drops me back down to 20, If I try to hold it, i'll feel an occasional jerk forward but it'll always cut back down to a rough 20.

Things I have done

Valve Adjustment
Cleaned the Carb
Tried 89 and 91 octane gas
Checked Carb Gaskets
Cleaned Spark Plug
Upgraded Spark Plug (NGK)
Cleaned the Air Filter (and removed for testing)
Checked Clutch Pads and Clutch Assembly (It's fine)
New Fuel Filter
Cleaned Float Bowl

Things I haven't done, but might try

Upgrade Exhaust Pipe
Upgrade the Carb / Intake
Try a new CDI / Magneto Rotor
Drill my Jet

Appreciate any advice. Thanks.
[/IMG]

 

[4banger]

When you mention your specs the gearbox is important.
You have the one of the worst, a pocketbike chain box.
Even your pic is hiding it like the dishonest sellers do. Bashful gearbox syndrome!

The stock carbs can be problematical.
Does your mixture screw have a brass plug covering it?

Did you clean the idle jet?

Best to get an NT or Speed carb to replace the original.
You will need a new manifold too.

Redline on the HS is 7800 rpm.

Finally found a post with my same issue. I have cleaned my idle jet....yes I do have a brass plug for the fuelx screw and I'm running 5g dual chain trans.....where should I start? I have my old Huasheng that use to hit 28, but needs an overhaul from moisture damage. Would you recommend switching out the cdi, I think the mag is fried. I've already tried my old carb and with it on the new engine it stalls and dies at 10 mph regaurd of adjustments so I think old carb is done too. New engine runs great but just like this post chops at 22 mph before redline. Help if you can thx