Troubleshooting a Huasheng 4-stroke Engine

Joined
Mar 18, 2018
Messages
30
Likes
6
#1
Hello MotorBikes.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.

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.
IMG_20180315_160922.jpg

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!
 

Attachments



CrazyDan

Well-Known Member
Joined
Jul 9, 2016
Messages
1,419
Likes
337
#2
Carefully drill a small hole in that brass plug then tighten a screw in there. Use the screw to twist that plug out. Enjoy being able to adjust your a/f mix.
 
Joined
Mar 18, 2018
Messages
30
Likes
6
#4
Carefully drill a small hole in that brass plug then tighten a screw in there. Use the screw to twist that plug out. Enjoy being able to adjust your a/f mix.
Thanks for the tip Crazy Dan! I have a few questions lol. First I drill a hole in the brass plug and somehow get it to pop out with the screw. OK great! How do I know if there's going to be a adjustment screw behind it for the A/F mixture. For all I know this cheap carb doesn't have the mechanism to adjust the A/F and put a brass plug in place. Don't want to sound cynical but I don't want to put in all that work and there not be anything behind the carb or just destroy it trying to get the plug out. Also should I just get a replacement carb with a A/F adjustment screw?
 
Joined
Mar 18, 2018
Messages
30
Likes
6
#6
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!
 

CrazyDan

Well-Known Member
Joined
Jul 9, 2016
Messages
1,419
Likes
337
#7
Just yank out the brass plug on the carb closest to your engine, the idle a/f mixture screw is hiding behind that.
 

CrazyDan

Well-Known Member
Joined
Jul 9, 2016
Messages
1,419
Likes
337
#9
To prevent folks from tuning it outside epa restrictions. Lean engines burn cleaner, but too lean = no fire. I prefer slightly on the rich side, engine runs cooler.
 
Joined
Mar 18, 2018
Messages
30
Likes
6
#10
To prevent folks from tuning it outside epa restrictions. Lean engines burn cleaner, but too lean = no fire. I prefer slightly on the rich side, engine runs cooler.
Gotcha! Alright well I'll give it a try. Just frustrating that they put that plug there. I'll try to take the plug out might save me a couple bucks if it works rather than replacing the carb.
 
Top