Troubleshooting a Huasheng 4-stroke Engine

M

Member 28661

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A half link might work in your situation.

Not sure if there's enough slack in the chain to take out a half link but I'll try. I saw a similar problem someone was having on their motorized bike with their chain having too much slack and couldn't take out a link. It was due to a large section of the chain being unsupported. I think the only fix permanently for this would be a chain tensioner. Currently trying to sketch a design for it.
 

old fart

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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.View attachment 81202
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. View attachment 81204
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!
I've had similar problems and the 'surging problem' on 2 of my 4 strokes. In both cases the problem was an air leak, experience from working on non computerized car engines was a dead give away. In your picture there is a hole with a plug in it to the right of the mixture screw. These 'plugs' are not solid but a cap shoved in there. This has been the air leak spot. Easiest way to diagnose if this is the problem is to use a piece of wooden dowel and 'firmly' plug it. Now try and start. hope that helps.
 
M

Member 28661

Guest
I've had similar problems and the 'surging problem' on 2 of my 4 strokes. In both cases the problem was an air leak, experience from working on non computerized car engines was a dead give away. In your picture there is a hole with a plug in it to the right of the mixture screw. These 'plugs' are not solid but a cap shoved in there. This has been the air leak spot. Easiest way to diagnose if this is the problem is to use a piece of wooden dowel and 'firmly' plug it. Now try and start. hope that helps.

Thank you for the advice! By the way great username lol. I've actually got the motor running, and it performs fantastic after my last carb cleaning. Currently I have a problem with one of my chains having too much slack, not enough to take a half a link out. A large portion of the chain is unsupported so I'm trying to design a chain tensioner for it. If you have any ideas that would be great!
 
M

Member 28661

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UPDATE: So The motorized bike is running! haha... First time going on a ride on it for a longggg time, since 2 years ago. Anyways I've installed a chain tensioner on the bike and it works well. Needs a tighter spring though. If anyone has a chain tensioner issue on the SBP 4-stroke shift kit, let me know and I'd be able to help you out with the mounting options....so forth. Anyways the reason why I'm updating this thread is because everything has not gone according to plan...as always. I have a couple issues I'm running into, first off I think the drive chain that I currently have on the bike is the wrong size. It's a 420 chain, I'm running into chain noise and I think chain slipping from what it sounds like. Thought the chain tensioner would fix this due to a large portion of the chain was unsupported, however it looks like the chain maybe the wrong size for this application. Any chain recommendations for the SBP kit?? Let me know.

Secondly, I thought my tune on the motor was great! Well...I thought it was lol. Everything changes when riding vs just idling the motor. Well I took the motor out for a test drive after I hooked up my chain tensioner and the motor ran OK for the first mile. Well after it really warmed up, when I was at a stop light it died on me and for the life of me I could not get it to start back up again. It would start then sputter out and die :(. Super frustrating when you're at an intersection. I tuned the motor according to these instructions: Try setting it with the idle rpm screw (the black plastic one) set at about 1 1/2 turns in and turn the screw behind the plug all the way clockwise then turn counter clockwise 2-2 1/2 turns. Let me know your recommendations for motor tuning, as it would be super helpful!

Thanks to this forum, as I've learned so much from it and everyone has been extremely helpful. Cheers to you guys!
 
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