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Ravenshurst

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Hi all. While I have built a handful of 2 stroke bikes, I have not yet built a 4 stroker.

Centrifugal clutch or torque converter belt? I am leaning towards the clutch because it will be cheaper, but I don't know which is best for my planned bike: 49cc engine, belt drive, 20" rim for the rear sheave. I weigh around 150, and Tucson is mostly flat. The bike will be a full cruiser, fenders, rear rack, Monark springer, disc brakes, etc. Top speed is not my prime concern.
I think that a centrifugal clutch will allow me to run a small enough pully to use the 20" on the rear wheel. Any thoughts on this? Also, even though speed is not of prime import, it would be nice to be able to get to school on time, lol. Any ideas what kind of top end this bike may be able to reach? And of course, any other thoughts, advice, or opinions are welcome. Thanks!
 
If you're talking about the 49cc Huasheng, the kits mostly come with a centrifugal clutch and a belt driven reduction transmission of a couple fixed ratios. Common sentiment is that the 49cc motors don't make enough torque for a torque converter. If you only weigh 150 and you're in a flat area, you'd be able to gear up no trouble. I'm about 210 and mine will cruise 27mph in the flats and takes off with no pedaling, so you should be able to to do better. I'm doing chain drive rather than belt with about 22:1 total reduction. Geared on the lower end for some hills in my area.
 
Thanks for the reply Knight. Honestly, I am not sure which particular engine. Probably a Huasheng if that is the most common. I am also not sure about a kit, as the sprocket, chains and gas tank would have to be replaced anyway. (I hate the kit gas tank) But it would probably be easier to buy the kit and replace stuff rather than buy everything one piece at a time.
So..as long as the kit comes with the centrifugal clutch, I guess I don't have to worry about making that decision, lol.
Again, thanks for the answer.
 
Ravenshurst said:
entrifugal clutch or torque converter belt?
49cc engine, belt drive, 20" rim for the rear sheave.

Any ideas what kind of top end this bike may be able to reach? And of course, any other thoughts, advice, or opinions are welcome. Thanks!
Click to expand...
Hi Raven, I am in Phoenix.
You need about 99cc engine to pull a torque converter and have any power left.
Cent clutch is best.

As far as speed goes, that is all about gearing to put the torque curve and power curves in the right place.

That is tricky with a direct drive system but a moot point with a shifter.
With just 3 gears you can climb a pretty steep grade without pedaling in low, and hit 40+mph in high.

There are 2 types of centrifugal clutches, and they are directly related to the engine you have.

Most engines have a 5/8" long keyed shaft output.
e.g. the HS 142FG 49cc and Honda 50.

Most transfer cases for them rely on an oilite bushing to support the clutch bell AND the tension on the belt drive reduction pulley like the 7G.

This is a known issue and a really a poor design that requires a lot of maintenance to get a useful life out it, as trying to make the transfer case just part of engine with just a bushing on a rotating shaft in the drive train anywhere is a cheap fail point.

The other option is isolating the transfer case from the engine.

This involves both belt drive pulleys to be on their own dual bearing supported shafts, and the clutch bell attached to the end of the shaft of the small primary pulley like the 4G #1C.

That means an engine with no protruding drive shaft, it has to have a short shaft with a clutch already attached like the HS 142F-1G 49cc.

There is also an HS 144-1G 53cc engine for that system for a bit more power from the same engine, kind of like a factory bore job for .2 more HP.

Hope that helps.
Good luck with your build!
 
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