Building a 4-stroke bicycle


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10:22 AM
Jan 31, 2024
So I am a new user, and have been researching 4-stroke vs 2-stroke engines. I have been seeing conflicting reviews on what kits to buy, and where to buy them from. I want to put a 4-stroke with a belt drive on a bicycle. I see that most people put them on a cruiser, but I would like to put one on lets say a mountain bike. I did see mentions of a steel frame and not an aluminum frame. I also saw mentions of Hondas engines such as the GXH50 or even the newer GX50. I saw another post about the huasheng 142f as well.

I am mechanically inclined just not sure where to start with all the conflicting information out their.

What do you experienced members suggest, and what should I look out for?
Do you guys recommend a certain brand?

Well if you are planning on a belt drive transmission for the gx50 or the 142f. I would buy a grubee 4G trans. Either of them engines are good.
So that's the thing I'm not sure what brand or where to buy a 4 stroke engine from. In my research some users suggested getting one from Ebay, some suggested another website.

I just want a decent 4 stroke engine kit with a belt drive.
The main reason people use cruisers with 4 stroke kits is mainly space. They take up more room than the 2 strokes, so a MTB may prove a unique challenge.

As far as engines. Genuine Honda is always a good way to go if you can. The cheaper 4 strokes still seem to generally do pretty well, so if you are on a budget you will still be pleased.

Most kit components do tend to leave something to be desired, so be prepared for that. Good way to get started at least, and you can upgrade later.
And since you're looking at mounting one in a mountain bike frame, check out this thread
I bought a Huasheng 142F with a 7G Ghost Racer belt drive off E-bay about 3 years ago. I'm not sure that the 7G is available today. The 142F comes with either a straight or tappered shaft. My 7G is designed for a straight shaft.

The Grubee 4g models have either a 4:1 or 5:1 ratio which you'll need to determine using a speed calculator. I believe the 4G models are designed for a tapered shaft. Double check this with Grubee before ordering because an engine purchased elswhere will have to be compatible. Grubee seems to be the only source for a belt drive, although I haven't looked lately.

Word of warning: Although E-bay has great prices, you're taking a chance. I have found the pictures quite often do not match the discription. You might end up with a chain drive, which in my opinion are all pretty much junk. Watch the YouTube videos on that. Belt drives are the way to go. Arguing with an E-bay seller is always a hassle. There are distinguishing features on the casting which will give you a clue as to what's inside. PM me if you ever need this info. On a 142f you will want to do the clutch bushing or bearing conversion that Mike St has documented on this site.

The 142F is a great alternative to that expensive Honda from which it was cloned. Mine runs great and has given me no trouble at all. They run lean but drilling out the jet will fix that. I experienced a vibration from the get go which turned out to be the 100T aluminum pulley. The shaft hole was drilled at an angle which made it wobble as it spun. I had to replace it, but you will be hard pressed to find one today. There are no replacement parts for my 7G trany except for the belt. GruBee has a better quality control and Don would never allow this. That's why I would buy only from him. And ask him anything about a belt drive if you want a truthful answer.

If for what ever reason you decide against a belt drive I would not even consider any of the chain drive tranies that are full of grease. At that point look for a straight shaft engine and design a jack shaft set up with a Max Torque clutch that you can buy replacement parts for including different springs which control the lock up rpm. I am currently building one like this in the thread shown below. I hope this is of some help. There is so much research to do before making an informed decision. It's nice to know what you'll be up against going in. Best wishes. m
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Building Michael's OCC with a 79cc Predator
Why a mountain bike? I know you're not going to ride this down the mountain side. Suspension front forks and disc brakes can all be fitted to larger frames that can hold a 4 stroke engine. There are physical dimensions available for the 142F. Make a cardboard template and try it in different frames.
Hi guys. Great replies very informative. I will try to answer some of these.
I wanted a mountain bike since they are thinner, and lighter. Perhaps I should link some that I have been eyeballing on amazon that have a very open v-frame. Hell these may not even be the typical mountain bikes that we are use to. They had a lot of space in the frame where you mount the engine.
As for speed. I am 5-11 and 145 pounds so 30mph would be my target goal, and I would be happy with that.

I did some research on the Honda engines like the newer GX50, but I did not find a kit for that.

I did view this website:
Seems peeps have had good luck with this 4 stroke
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