Troubleshooting a Huasheng 4-stroke Engine

Mar 18, 2018
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Hello Motor Bicycling.com I'm Matt, a new member to this forum, however I've been working at this motorized bike for close to 3 years now and I've only got it running a hand full of times unfortunately. First a little bit of background about the bike. I first purchased the Huasheng 4-Stroke engine kit at GasBike.net along with the 4 stroke shift kit at Sickbikeparts.com back in 2015. Also purchased a mountain bike and upgraded Shimano hydraulic brakes. After having assembled the bike in the summer of 2015, I did manage to get it running a hand full of times with the top speed clocked at 45mph. After about 2 rides on it I noticed the engine mount was sliding downward on the frame thus putting slack in the chain, fixed the issue with the mount.
IMG_20180315_160922.jpg

After having the motorized bike sit for quite a while roughly 2 years, I tried to start it up again recently and it wouldn't fire up. So I took apart the carburetor cleaning every part meticulously (tons of old fuel lacquer inside the carb), cleaned the fuel tank, put in new fuel lines, new fuel filter, new on/off fuel valve and new fuel. I also replaced the cheap chinese spark plug included in the kit with an new NGK plug.

This boils down to the current issue that I'm having with the Huasheng 4-Stroke 49cc engine not wanting to start no matter what I try. After replacing most of the fuel components, new spark plug and carb cleaning it's still a no go. I've even tried pulling the throttle a little bit to put some fuel in the cylinder when pull starting it, but it still doesn't start up. I've also looked at the engines compression and it looks good.
IMG_20180315_160951.jpg


After doing some research online I've come to the point that I think the reason for the bike not starting is that the air-fuel mixture is off. Doing some research I've found that the mixture can be adjusted with a screw located on the back of the carb(pictured above). It appears that the carb that came with my motor has a brass plug in the place of the adjustment screw.

Would this be a problem with the air-fuel mixture? If so should I replace the carburetor, and what carburetor would you guys recommend?

Hoping to get this motorized bike project up and running as soon as possible!
 

Dan

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May 25, 2008
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Hi Matt, welcome!

Just what I would do. Put the old plug back in, take air cover off and try some starter fluid.

Fine tune from there. Sitting as long as she did, might take a try or 3.

Go about everything in a slow and relaxed manner with clean, new gas.

One thing at a time.


This is important with any pull-start.

1; pull cord until you feel the height of resistance. (if it gets easier. Allow pull cord to retract and do again)

2; After the pull cord is/offers the most resistance. Allow it to slowly retract.

3; Give pull cord a solid, sharp pull.

4; repeat as necessary, after a moment. Slow and gentle except for the sharp, hard pull.


They are amazingly good lil power plants. Show 'em some love and like a puppy, they want to please
 

Dan

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May 25, 2008
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Moosylvania
Please, please tell me your engine is not zip-tied to your bike?

That is really not a good thing.

(I'm not great visually. forgive me if I got that wrong)
 
Mar 18, 2018
6
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Hi Matt, welcome!

Just what I would do. Put the old plug back in, take air cover off and try some starter fluid.

Fine tune from there. Sitting as long as she did, might take a try or 3.

Go about everything in a slow and relaxed manner with clean, new gas.

One thing at a time.


This is important with any pull-start.

1; pull cord until you feel the height of resistance. (if it gets easier. Allow pull cord to retract and do again)

2; After the pull cord is/offers the most resistance. Allow it to slowly retract.

3; Give pull cord a solid, sharp pull.

4; repeat as necessary, after a moment. Slow and gentle except for the sharp, hard pull.


They are amazingly good lil power plants. Show 'em some love and like a puppy, they want to please
Those 49cc motors when they work are amazing! Great on gas and put out great power for the given job!

I'll give starter fluid a shot see if that will put life into her. In that case if starter fluid does work than I think that would confirm it's a fuel problem due to the carb.

Funny enough I've tried pull starting it with that method, slow than a sharp hard pull, and my arm was just sore lol. Just wont turn over.

Thanks for the advice though!
 
Mar 18, 2018
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Please, please tell me your engine is not zip-tied to your bike?

That is really not a good thing.

(I'm not great visually. forgive me if I got that wrong)
Haha :D it's not. I can see how it can seem that way from the picture however the engine is securely mounted. The engine mount is held to the bike frame with fabricated exhaust claps.
 

Dan

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Staff member
May 25, 2008
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Moosylvania
Ah, cool.

Sorry for the rudimentary. Wasn't sure and always good to ask the basics when trying to help.

Please do post on how it's going.
 
Mar 18, 2018
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It's all good! Will do, I'll post updates about the bike. As I've kept this build private for too long lol, been meaning to make videos about it but haven't had the time.
 
Mar 18, 2018
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UPDATE: So after much testing I've come to the conclusion I thought I would come to but had to make sure! So after purchasing some starting fluid at a local auto parts store, I sprayed about 3seconds worth into the carb (directions from the starting fluid ). After about 3 pulls...BAM! It started up and slowly died :(. So what I'm thinking is, it's getting air, spark, and compression is good. The fuel line is letting fuel in. I know this because after taking the fuel line off and opening the fuel valve, the fuel was flowing fine. So this leads me to believe that the A/F mixture is completely off and/or there is a problem with the jet.

So I think the best way to go about this is to purchase another carb. This is where I will need your help everyone. I'm looking for a new carburetor to put on the motor, one with A/F mixture adjustment. If it's a racing carb, even better. I hear those can give better air flow. The motor is a HuaSheng 49cc Honda clone.

Looking forward to have this project up and running soon, so please comment your carb recommendations for this motor!
 

Dan

Staff
Staff member
May 25, 2008
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106
48
55
Moosylvania
Working here, I can't recommend any supplier In particular. I'd forget some body and it's not good.

As you have cleaned your carb, and I would try that again. Might try rejeting before spending more. But in rereading, seems like it's been bad from the git-go.

Are you using the choke when starting?