Huasheng 49CC 4-Stroke Engine Stalls

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Jul 21, 2018
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#1
Brand new engine starts up fine after a few pulls and runs great. However, when I come to a stop, the engine stalls and I have to re-start. Any ideas?

Thanks in advance - much appreciated.
 


FNTPuck

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#3
Is the engine bone stock, or has it been modified in any way? Have you tried adjusting the idle screw?

Need quite a bit more info, but the motor should have an idle screw on top and then the idle mixture screw that is normally capped with a flush brass plug near the motor. Some have said that their capped off idle mix screw was completely leaned out all the way out from the factory! Rotating it out 1-2 full turns should help a lot if that is the case.

Always make sure engine is warmed up when adjusting for idle, and make small changes at a time giving the motor 10-15 seconds to adjust between changes.

Once you get it to idle properly, it is a good idea to do a plug chop and see if the fuel adjust screw needs to be messed with as well. Main jet shouldn't need to be messed with unless you have done intake and exhaust mods, so the good news is you should be able to get her running great with only some time and a screw driver :).

edit: swapped the descriptions on the idle and fuel screws.
 
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#4
Before you go messin' with the carb, make sure your sparks are in order.

Remove the shroud and rotate the flywheel until the magnets pass under the coil. Slip a business card between them; it should just fit. If it's too loose, you'll lose spark at idle/low revs. It's possible the magneto itself is failing, but that's usually an all-or-nothing deal. To check it, remove the plug (or use a spare), connect the plug wire to the plug and hold the plug against the engine so you can see the gap. Tug the starter a few times. Look for a weak yellowish spark (that's as good as it gets).

If you've got spark, proceed with carb adjustments as above.
 

darwin

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#5
Shouldn't spark be a nice blue jolt? That;s the old rule to go by on cars. Maybe it's different on these lil motors?
 

MotorBicycleRacing

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#7
Is the engine bone stock, or has it been modified in any way? Have you tried adjusting the idle screw?

Need quite a bit more info, but the motor should have an idle screw that is normally capped with a flush brass plug and then the fuel adjust screw. Some have said that their capped off idle screw was completely leaned out all the way out from the factory! Rotating it out 1-2 full turns should help a lot.

Always make sure engine is warmed up when adjusting for idle, and make small changes at a time giving the motor 10-15 seconds to adjust between changes.

Once you get it to idle properly, it is a good idea to do a plug chop and see if the fuel adjust screw needs to be messed with as well. Main jet shouldn't need to be messed with unless you have done intake and exhaust mods, so the good news is you should be able to get her running great with only some time and a screw driver :).
You must have never had your hands on a HS carb because your info is incorrect.
The idle screw is not possible to cap and is the the big black philips on the top of the
carb that only adjusts the pull on the throttle cable.

On the left side of the carburetor near the front is the idle mixture screw that may be capped.
On the HS motor the idle mixture screw is a fuel adjustment, not an air adjustment.

In order to adjust the carburetor it is necessary to warm the motor up first.
The motor should have at least 5 minutes running time before any adjustments are made.

The average setting is 2 turns out [1.75 ~ 2.25 turns]
Simply adjust the screw for maximum idle, and then turn the screw approx 1/16" counter-clockwise [slightly rich].

Check the throttle response, and adjust the mixture if there is a hesitation.
Turn screw clockwise if it "bulks" and then catches on [rich],
or adjust screw counter-clockwise if it accelerates and then drops off quickly [lean].
 

FNTPuck

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#8
You must have never had your hands on a HS carb because your info is incorrect.
The idle screw is not possible to cap and is the the big black philips on the top of the
carb that only adjusts the pull on the throttle cable.

On the left side of the carburetor near the front is the idle mixture screw that may be capped.
On the HS motor the idle mixture screw is a fuel adjustment, not an air adjustment.

In order to adjust the carburetor it is necessary to warm the motor up first.
The motor should have at least 5 minutes running time before any adjustments are made.

The average setting is 2 turns out [1.75 ~ 2.25 turns]
Simply adjust the screw for maximum idle, and then turn the screw approx 1/16" counter-clockwise [slightly rich].

Check the throttle response, and adjust the mixture if there is a hesitation.
Turn screw clockwise if it "bulks" and then catches on [rich],
or adjust screw counter-clockwise if it accelerates and then drops off quickly [lean].
Lol my description of the two was flipped but you said the same exact thing I did. I just mixed the two up when typing it, and am editing it to fix that.

I do have one on my desk right now, and removed the brass plug to check the adjustment. Mine was not maxed out, but I have seen people say theirs was.
 

TruewoC

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#11
its either your idle being too low or your clutch is sticking. try increasing your idle. if the problem still occurs then take off your clutch assembly and add some hi-temp grease on the shaft.
 

TruewoC

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#12
its either your idle being too low or your clutch is sticking. try increasing your idle. if the problem still occurs then take off your clutch assembly and add some hi-temp grease on the shaft.
oops. nevermind. the clutch on these are different than what i was thinking. i thought they had the clutch bell that are usually on minibikes. in that case just adjust your idle
 

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