High RPM low speed

[Tanner Logan]

Just installed my HuaSheng 49cc 4 stroke with minimal problems in that field. However now in the riding phase when I try to accelerate the engine RPM's are higher than the speed output. There is no air mixture screw on the carb just an idle screw and adjusting it doesnt help at all. The engine will only run with the choke half on or else it will die out. It also seems as if there is a bit of air coming from the top of the engine, willing to bet this shouldnt be happening but a little unsure because all past builds were two stroke. Cant seem to find anything that works as far as a fix online.

New to the forum world so I apologize if this is in the wrong section. ANY help would be greatly appreciated or if anyone in town could help point me in the right direction that would be more than welcomed.

 

[ProDigit]

1- Don't run your engine at high RPM in the breakin period.
2- Install a smaller rear sprocket, for better top speed at lower RPM (acceleration may be less)

 

[MotorBicycleRacing]

There are a few HuaSheng 49cc 4 stroke kits.

Can't give you specific advice without knowing what gearbox it has
and where you bought it from.

There is an air mixture screw on the carb under a round brass block
off plate that was installed so you couldn't mess with the settings.

Drill it out.

Is the air coming from the top of the engine from the cooling fan
under the shroud?

 

[Tanner Logan]

Any idea on the choke having to be at half notch or the air coming from the top?

 

[Tanner Logan]

Ordered from BikeBerry

http://www.bikeberry.com/gas-engine...g-pull-start-bicycle-engine-kit-4-stroke.html

HuaSheng 142f


So there IS in fact an adjustable screw under this brass block. I was wondering why others online had the option and mine did not but didnt want to go drilling and prying until I was sure. After some research the air is coming from the fan and no alarm there.

 

[MotorBicycleRacing]

1- Don't run your engine at high RPM in the breakin period.
2- Install a smaller rear sprocket, for better top speed at lower RPM (acceleration may be less)

Have you ever had or ridden a 50cc Huasheng 4 stroke?

The 4 strokes can be revved up to their redline of 7800 rpm during
break in with no problems, just don't hold it there for extended
periods.
Seeing that we don't know what kit he has your gearing advice
is rather premature.

 

[MotorBicycleRacing]

Any idea on the choke having to be at half notch or the air coming from the top?

You didn't answer my questions.

 

[ProDigit]

Have you ever had or ridden a 50cc Huasheng 4 stroke?

The 4 strokes can be revved up to their redline of 7800 rpm during
break in with no problems, just don't hold it there for extended
periods.
Seeing that we don't know what kit he has your gearing advice
is rather premature.

Not really.
The advise is solid for ANY engine!
Everywhere they say NOT to run an engine at high RPM. You may damage the cylinder walls, piston rings, etc...
Start slow, and do some slow WOT revs to 5 or 10MPH, and engine brake.
That's the best routine.

Revving a 4 stroke to the redline at breakin is REALLY bad advise!

Been working with scooters for several years now. Same rules apply there as well.

 

[Tanner Logan]

It is the far left brass correct? I started to drill then got a little nervous about whether or not it was the correct one. Should I continue this tiny hole and pry from there? Or drill it out entirely with the same size(as the brass cover) drill bit?

Engine info/Order info in post 5

 

[MotorBicycleRacing]

It is the far left brass correct? I started to drill then got a little nervous about whether or not it was the correct one. Should I continue this tiny hole and pry from there? Or drill it out entirely with the sane size drill bit?

Engine info/Order info in post 5

Yes, drill the one on the far left that is closest to the motor.

Don't pry, use a larger bit that is almost as big as the plug.

If you had the carb off you would see the tip of the mixture screw in
the carb throat.

When you get the plug out please note how many turns in clockwise
until the screw lightly bottoms out and let us know here.

I would like to know what their EPA mixture screw setting is.

The standard starting point is 2 to 2 1/4 turns out.

Does your Huasheng motor have a C.A.R.B. sticker on it? I am sure
it doesn't but Bikeberry claims it is C.A.R.B. approved.
Can you take a pic of the EPA sticker and post it here?
Thanks

 

[MotorBicycleRacing]

Any idea on the choke having to be at half notch or the air coming from the top?

You got the air right.

Those carbs are notorious for the idle jet blocking very easily.

Was the motor run in the factory?

Remove the black idle screw and carefully pry out the black
plastic block under it.
Take a small piece of wire and thread it through the jet to clean.

 

[Tanner Logan]

It took two full clockwise turns to fully tighten. In order to get better top end I would need to turn counterclockwise to increase air flow correct? This is why the engine must be on half choke to run?

Attached image is the only sticker on the engine. Can you figure anything out from there or do you need a sticker placed elsewhere?

 

[Tanner Logan]

I have removed idle screw already and poked through the jet to clean it. It still had trouble running without the choke on. Not sure if it was run in the factory. There was a slight trace of oil in the reservoir so it leads me to believe that it might have been but not quite sure.

 

[MotorBicycleRacing]

It took two full clockwise turns to fully tighten. In order to get better top end I would need to turn counterclockwise to increase air flow correct? This is why the engine must be on half choke to run?

Attached image is the only sticker on the engine. Can you figure anything out from there or do you need a sticker placed elsewhere?

Thank You!
There is no other sticker. Just that 2012 EPA one.
Try 2 1/4 turns out

Does it idle with the choke off?

Oil in the reservoir could be from assembly.

 

[Tanner Logan]

No it will not idle without the choke at least half on. It did not do this the first few times I cranked and ran it(not driving just sitting in place). This just started after a ride around the block on literally the first test drive.

 

[MotorBicycleRacing]

No it will not idle without the choke at least half on. It did not do this the first few times I cranked and ran it(not driving just sitting in place). This just started after a ride around the block on literally the first test drive.

Do you have an inline fuel filter?

Is the tank rusty, dirty?

You gotta clean the carb thoroughly and blow it out with air.
make sure you remove the plastic float, etc before you hit it
with air.

 

[ocho ninja]

Have you tried unscrewing the main jet and cleaning that out?

Try some carb cleaner and give the carb a full tear down and clean out ?
Also we are still trying to figure out what gearbox and rear sprocket you have?

 

[MotorBicycleRacing]

Not really.
The advise is solid for ANY engine!
Everywhere they say NOT to run an engine at high RPM. You may damage the cylinder walls, piston rings, etc...
Start slow, and do some slow WOT revs to 5 or 10MPH, and engine brake.
That's the best routine.

Revving a 4 stroke to the redline at breakin is REALLY bad advise!

Been working with scooters for several years now. Same rules apply there as well.

Amen!

For break-in.....ride it like you stole it using a quality petroleum based oil. Do not rev past 9,000rpm if and until the engine is infact brokin in. Change oil frequently and ride every day!

 

[Tanner Logan]

The tank was a bit rusty but I put some gas in, shook it up, drained it then let it sit dry before using it. Seemed to work pretty good for the visible nastiness that was there. I have it on a Schwinn S1 and the way the frame is setup the tank is just a bit further back therefore closer to the carb. So I cant quite fit a fuel filter on at the moment but it is SOON to come once I get more fuel line. Could that be effecting it that much?

There is a 52 tooth sprocket on the back wheel so it could be that it just isnt getting a high output revolution. I'm thinking reduction gear box? Not quite sure still brand new to all this.

I have yet to tear down the carb and clean it thoroughly however that's the next step. Have to wait for morning to get a can of compressed air.

 

[Tanner Logan]

Update :

So I took apart the carb and cleaned everything thoroughly. Not a single bit of dirt or blockage in ANY way. I have learned that I in fact had the choke on as opposed to off. Yes yes I know believe me I am making fun of myself RIGHT now.

However this brings on a new question. Why is it that when I attempt to turn the choke off the engine revs like crazy and begins to take off. I cannot even turn it 25% without the RPM's shooting through the roof and the bike taking off. I have tried the air mixture screw in all positions but cannot understand why this is happening. It's as if I was running full throttle and I even have the throttle cable out at the moment. ANY further help would be greatly appreciated.

 

[ProDigit]

Have you checked your idle screw?