Chinese 139F 4 stroke engine kit

[Epicurus54]

I am posting from this site having just joined up. I wish I had have known it existed before, because it is excellent.
I have just bought and fitted a 31cc Chinese 139F 4 stroke kit to my mountain bike and I think I have been ripped off.
I expected it to be gutless given that Australia has a maximum allowable power of 200 watts, but it continues to conk out on me for no apparent reason, although it is easy to restart. Does anyone know anything about the motor?
They also claim that the power can be increased on it but I don't know how.
I also find the belt drive and the ring it is attached to very flimsy and I can't see it lasting too long.
Can anyone recommend a better quality 4 stroke kit should I continue to be disappointed with this one? I was thinking of getting a Honda 50 scooter and fitting it to my bike myself.

 

[Alaskavan]

I don't know anything about your engine. As for better quality 4-strikes, there are a few options. A lot depends on wether you want frame mount, or are willing to look at rack mount.

 

[gone_fishin]

i dunno about your engine/kit either, but quick research
shows a chinese 139f is either 31cc/2-stroke or 36cc/4-stroke...

can you link us to where you bought your kit?

 

[Epicurus54]

Thanks fellers. It is rackmounted but I don't mind the idea of frame mounted.
I bought the kit from Australian ebay from a Chinese-Australian importer. He puts it on for auction, even though it is sold as "buy it now" so I don't know if it is possible to link you to it, and if it is I am too computer illiterate to link you to do so.
It is true that the only thing we can learn from history is that humans learn nothing from history, but I like to think that had I have known someone who knew something about them I would not have bought it. Unfortunately motorised bikes are just taking off over here and the ignorance on the subject is unlimited.

 

[gone_fishin]

then i can honestly say i think you should shop golden eagle's site, it's "belt & drive-ring" done right. go have a look at the "rack-mount" forum to see some excellent member-input about the system.

and, might could be a chance (if you can solve the engine problem) that you could buy the kit-only.

about the engine...i think you should have a look at your fuel vent. if you can run it without the cap on, or have another one, try that. only a guess, tho.

 

[Alaskavan]

The 31cc claims a about 1 hp and the 36cc about 1.5. Pretty low power. I guess zbox doesn't sell 4-strokes there? If a Whizzer is out of the question, and rack mount is cool with you, I'd advise looking at Golden Eagle or Staton. Their products are high quality.

 

[Epicurus54]

Thanks very much again fellers. I will take your advice. I don't mind getting something a bit more powerful than 200 watt, even if it means I am breaking Australian law. The coppers don't really give a rat's butt when they someone like me riding something so small.

 

[Irish John]

Thanks fellers. It is rackmounted but I don't mind the idea of frame mounted.
I bought the kit from Australian ebay from a Chinese-Australian importer. He puts it on for auction, even though it is sold as "buy it now" so I don't know if it is possible to link you to it, and if it is I am too computer illiterate to link you to do so.
It is true that the only thing we can learn from history is that humans learn nothing from history, but I like to think that had I have known someone who knew something about them I would not have bought it. Unfortunately motorised bikes are just taking off over here and the ignorance on the subject is unlimited.

There's a wealth of knowledge about motorised bikes on this site and plenty of it comes from the Australian contributors. I know the guy who sold you the motor. He is selling grubee kits now - after saying he'll have them in stock next week for over a year. I reckon he's that sort of guy. His price is on the high side but ZBox also are getting 4-strokes only it's the Huangsheng with JL Hoot gearbox and I think a fixed sprocket drive. A freewheel drive sprocket is very essential for safety and a freewheel hub alternative is a real headache cos I think you have to completely rebuild the wheel. ZBox are reputable and decent so I reckon you should try them. For an extra $50 you can air freaight the Grubee kit from the US from Bicycle-Engines.com and that has a freewheel sprocket as standard. What worries me is where can people get parts for Huangshengs. The Grubee gearbox will also fit the Honda and spare parts not such a problem with those in Oz.