139cc four stroke on Mini scooter

[Cassera]

I was wondering what you guys think of a 5hp 139cc four stroke engine on a mini scooter.

The scooter currently has a 35cc 1.8hp two stroke engine
This is the exact scooter we have http://www.youtube.com/watch?v=eBTO-14oIwA

The stock clutch gear has 14teeth on it....Assuming I put a gear with 15-16 teeth on it with the 139cc four stroke 5hp engine, How fast do you guys think top speed will be?

The 139cc is from a snow thrower.

Do you guys think I should throw the four stroke in there? Or build the two stroke?

This scooter is going to be used specifically for riding on paved roads for top speed with decent acceleration...

Any thoughts or suggestions??

 

[Cassera]

NOBODY has ANY input what so ever on this??

 

[robbie]

One thing you'll have to look out for is chain sizing. Is your current drive train set up for #25 chain? That's 1/4" from the center of one roller to the center of the next. If so, then you'll have to decide whether to change the rear sprocket and chain, or get a #25 drive sprocket. This could be an issue because most of the equipment you get for larger engines is compatible with larger chain.

I have a pocket bike engine that had a #25 output sprocket, but I when put a CVT on the engine I found out the CVT is for 8mm chain, so I had to get a different sprocket for the wheel. That wasn't a problem because I found one with a 3 hole pattern just like the pocket bike hubs. But I want to make another bike with the same engine and CVT, so I wanted a sprocket with a 4 hole pattern. When I got one I found out that it doesn't match the 2-7/8" circle that's found on most mini bike and go kart hubs. It's metric, so I'll have to drill new holes if I want to use normal mini bike parts.

Just make sure your parts all match before you spend money.

 

[Cassera]

It's actually belt driven.....Thanks for the input though

 

[robbie]

You mentioned the tooth count on your clutch, so I figured you'd be switching over to a chain drive. If you're going to do that, you'll have to go through the same process I did, looking for compatible sprockets.

If you keep the belt system, you could get a centrifugal clutch with a belt pulley and go straight from there to the wheel with no ratio reduction. It should be fast enough.

 

[solomon]

you need to change the ratio because the 2 stroke revs higher than the 4 stroke.

 

[robbie]

How fast do they rev? I wonder if the 2 stroke can even get to top RPM, considering how small it is.