2 Stroke gearing (w) clutch on jackshaft ?

[wwwdotgov]

I recently picked up this little 2 stroke Kohler engine for a future project.
There is really no good way to mount the clutch on the crankshaft on this motor, so I'm going to weld a sprocket onto a matching crankshaft plate and bolt it on. The clutch will be on the jackshaft.

Now the gearing is where I'm a little lost. :shrug:

I know that "usually" when mounting a clutch on the jackshaft, you want the same 1:1 ratio with the sprocket on the crankshaft.
But because this is a 2 stroke, it won't have low end torque like most engines.
So would it benefit me to use a 9 or 10 tooth sprocket on the crankshaft and a bigger 11 tooth on the jackshaft clutch? That way the clutch won't engage right off idle and until the revs are a little higher. I don't know how to figure the math on something like this?

I think the smallest sprocket available on most max-torque clutches are 11t. I know there are more expensive racing clutches that have some adjustability on when it engages, but I'm trying to keep this next project affordable.

Any thoughts or input appreciated! :thumbsup:

 

[scootercat]

what size is the engine?...Hp?...Max R.P.M.s that it'll turn?...what is engagement R.P.M. of the clutch?...most are in 1500-1800 R.P.M. You could run it 3 to 1,engine to jackshaft....then the clutch at 11 tooth to a 60 tooth on the rear....if It'll spin 10,000 at 3to1 that will bring it down to 3333 R.P.M. at the Jackshaft then 5.45 to the rear wheel should be in the ballpark....Scootercat....

 

[wwwdotgov]

what size is the engine?...Hp?...Max R.P.M.s that it'll turn?...what is engagement R.P.M. of the clutch?...most are in 1500-1800 R.P.M. You could run it 3 to 1,engine to jackshaft....then the clutch at 11 tooth to a 60 tooth on the rear....if It'll spin 10,000 at 3to1 that will bring it down to 3333 R.P.M. at the Jackshaft then 5.45 to the rear wheel should be in the ballpark....Scootercat....

Hp and max rpm unknown? This is engine pulled from a U.S. Army generator that was made way back in the 1940's to early 50's. It's about comparable in size to a power products engine.
It never had a clutch. It was coupled straight across to a generator. (350watts and 15 volts at 30 amps).

3 to 1. What sprockets are we talking about on engine & jackshaft ?

I was imagining engine -to- clutch/jackshaft on first chain. Then jackshaft sprocket to rear wheel sprocket on second chain.
OR
Should it be engine -to- jackshaft sprocket on first chain and clutch/jackshaft to rear wheel sprocket on second chain?

 

[ZR9B]

We had at least 4 of those at our shop (owner bought them because they looked cool) and I think we found them to be 5HP....The rmps seemed low when we were playing with them....we never put a load on them because they were like 48 volt DC.....found the hp by google ...hope this helps...

 

[Oldsalt]

Hp and max rpm unknown? This is engine pulled from a U.S. Army generator that was made way back in the 1940's to early 50's. It's about comparable in size to a power products engine.
It never had a clutch. It was coupled straight across to a generator. (350watts and 15 volts at 30 amps).

3 to 1. What sprockets are we talking about on engine & jackshaft ?

I was imagining engine -to- clutch/jackshaft on first chain. Then jackshaft sprocket to rear wheel sprocket on second chain.
OR
Should it be engine -to- jackshaft sprocket on first chain and clutch/jackshaft to rear wheel sprocket on second chain?

The 'engine to jack shaft' chain should be regular sprockets. Say a 12 tooth on the engine and a 36 tooth on the jack shaft. That gives a 3 to 1 reduction. If that is too high or too low replacing the 36 tooth with a smaller or larger sprocket will fine tune your take off ability and your top speed which is always a compromise. OldMiniBikes has them for short money. The clutch on the jack shaft would drive the sprocket on the rear hub. Works good, that has been done lots of times.

What is the diameter of the rear wheel? That is an important factor in determining the probable 'final' gear ratio. Also what kind of riding are you contemplating...if you want to climb hills or ride it around a confined space with a lot of stop and goes the final ratio will be greatly different than if it is to make 50 MPH passes past the crabby old lady's house down the street.

 

[wwwdotgov]

The 'engine to jack shaft' chain should be regular sprockets. Say a 12 tooth on the engine and a 36 tooth on the jack shaft. That gives a 3 to 1 reduction. If that is too high or too low replacing the 36 tooth with a smaller or larger sprocket will fine tune your take off ability and your top speed which is always a compromise. OldMiniBikes has them for short money. The clutch on the jack shaft would drive the sprocket on the rear hub. Works good, that has been done lots of times.

What is the diameter of the rear wheel? That is an important factor in determining the probable 'final' gear ratio. Also what kind of riding are you contemplating...if you want to climb hills or ride it around a confined space with a lot of stop and goes the final ratio will be greatly different than if it is to make 50 MPH passes past the crabby old lady's house down the street.

Thanks Oldsalt! This will be for next project and probably confined to flats with no hills. I imagine 5" wheels or 6" max but we will see what comes on the next roller I purchase.
At this point I guess I know the sprocket to order for the engine so the machine shop can make a plate to house it in. Thanks again.

 

[grumpyed]

The engine is a Jacobson and is 2hp or a little less.Its about 6ci maybe 5

 

[ZR9B]

ours was made by Wisconsin motor corp....all but one were 2 cyclinder 4 stroke 16 cu inches ...the 2 stroke didnt have any info on it....both were 28 vdc ...I only have pics of the 4 stroke.... .sorry if I screwed any one up...