4-stroke direct drive to ŗear wheel?

[taureanirishman]

I'm 200# with a steel frame cruiser, I was looking to do a 4-stroke buikd with a 100cc HF motor with no reduction drive, jackshaft, etc...

I've seen some bikes with this build, but am wondering about clutch longevity.

My other option is a gt-5 2-stroke. But looking at the extras i woukd need like mikuni carb & upgraded ignition, the price is basically the same as doing a 4-stroke build if there's no gear box.

Going to utilize a hub mounted sprocket either way. Could I run a 100cc directly to a 44tooth+ sprocket safely?

 

[wheelbender6]

If you don't want to run a jack shaft for reduction, you could use a belt and sheave.

 

[MotorBicycleRacing]

I'm 200# with a steel frame cruiser, I was looking to do a 4-stroke buikd with a 100cc HF motor with no reduction drive, jackshaft, etc...

I've seen some bikes with this build, but am wondering about clutch longevity.

My other option is a gt-5 2-stroke. But looking at the extras i woukd need like mikuni carb & upgraded ignition, the price is basically the same as doing a 4-stroke build if there's no gear box.

Going to utilize a hub mounted sprocket either way. Could I run a 100cc directly to a 44tooth+ sprocket safely?

Take a straight line from the sprocket on your engine shaft mounted clutch to the sprocket on your rear wheel.
How much would your motor be hanging out on the right side of your bike?

Do you know what your gearing ratio is with, say a 10 tooth sprocket to a 44 tooth?

You would need more like a 100 ++ tooth sprocket.

 

[KCvale]

I'm 200# with a steel frame cruiser, I was looking to do a 4-stroke buikd with a 100cc HF motor with no reduction drive, jackshaft, etc...

Look at a Wizzer, they run just a clutch with a pulley to a giant pulley almost as big as the 26" wheel and even then don't have much low end speed before the clutch slips, but hey if you want ride 50+MPH on a bicycle that'll do it.

 

[MotorBicycleRacing]

Look at a Wizzer, they run just a clutch with a pulley to a giant pulley almost as big as the 26" wheel and even then don't have much low end speed before the clutch slips, but hey if you want ride 50+MPH on a bicycle that'll do it.

Whizzers do not run one belt from the clutch to the back wheel.

If you Look at a Whizzer you will see a 2 belt reduction jackshaft.

The Whizzer rear wheel sheave is not that big at only about 15"

 

[KCvale]

The point was how big the rear sprocket would have to be to run without a reduction is all.
We both know this direct drive is folly, just a suggestion of what it would take.

 

[wheelbender6]

I'd say you need a sprocket about the size of this one for direct drive.

Here is the direct link if you can't see the pic:
http://www.instructables.com/id/Motorized-Bicycle-DIY-The-hard-way/

 

[SunkyWorks]

With a 11t #35 clutch and 20" wheel on a rear rack, IF you could mount a
80t rear sprocket. This would give 41 mph at 5000 rpm. (Governor removed)
Rider would need to do some pedaling on start.

Speed Calculator For Go Karts and Mini Bikes
http://www.diygokarts.com/speed-calculator.html

80T Drive Sprocket for #35 chain, Manco 9986
Center hole is 1 3/8" diameter

 

[KCvale]

I'd say you need a sprocket about the size of this one for direct drive.

Here is the direct link if you can't see the pic:
http://www.instructables.com/id/Motorized-Bicycle-DIY-The-hard-way/

It would need to be bigger than that, there is a Q-matic reduction on the engine.

 

[ronphelps]

Hello, I have a beach cruiser bike that I have put a 79cc HF motor on and it works great I love it and get a lot of comments on it. It will go up hills no problem although I do have The pedals I mainly use them for foot support. I recommend using a jackshaft, very easy to install and gets the most of the small engine. I am also 200lbs. The bike will do 30mph easy maybe more but 20 to 25mph is perfect to cruise on. I got a lot of the info to build here on this forum and on youtube. Don't cheat on the build put a jackshaft on. Here is a photo of mine Get the Professor to give you the gearing it's easy. good luck