139fmb Engine
 

hello Guys, Im new on this forum so excuse me if the thread aint in the right place.

I have recently acquired a kinroad chopper styled 50cc bike but
here is the catch tho, it came without an engine..
My budget doesn't allow me to blow it all on a nice japanese engine, so one of the chinese clones will have to do.
Been researching for a while now, and it seems china's best answer stands between zongshen vs lifan vs gpx. ( Any brands I'm missing?)

Im looking to start of with a 50cc, then some day later down the line add some performance parts to it ( bbk,cam,crank,carb)
Unless its possible to restrict the top speed of a 110cc or 125cc engine to 25mph? and to fool the cops :)

So for the 50cc engine Im looking for a solid platform with Loads of aftermarket/tuning parts.

Any help in the right direction will be most appreciated

If you only want to go 25mph ,you don’t need a single performance part even on a 50cc ,we used to get that out of a stock z50 with 8”wheels .

The Chinese clone engines are very good. I'd put in a 125cc and just be careful not to go too fast when there's a chance of being pulled over. It's highly unlikely a cop could tell the difference between a 50cc and a 125cc. Most cylinders have the displacement marked on them but its not that obvious, and the numbers could be easily ground off.

I live out in the country so blasting around with a 125cc its not a problem normally.
But there may be times where need to use it as regular transportation into more populated
cities where sharks lurk at every corner :$

The police here roll with a portable dyno of sorts, but it only measures the top speed.

Do you guys think there is a way to restrict a 125cc to only do 25mph? maybe by messing with cdi and chain sprocket ratio?

You could put a small carb on it. Put so much slack in the cable it won't open the throttle all the way. They even have the throttles for the kids atvs and bikes that have a throttle limit screw.

You can always run 50% water in your gas !

The water method woule be too easy ;) I guess I just like to go the difficult way about it, Im sure you understand.

Restricting the throttle cable play, and fitting a smaller carb is a good idea. Then maybe add a rev limiter or something of that natur? Could the sprocket idea work, or is it not possible?

Sprocket would work. They go all the way down to 10 tooth on the front sprocket.

What you need is a Snuff-R-Nut with a small enough opening to restrict speed to 25. 1 second to open or close it even when riding.

So it would be possible to get it down to around 25mph?
If that is the case, what engine size would be better as far as:
Availble service and tuning parts and overall longevity\reliability?

107cc (152fmh) vs 125cc (154fmh)