Dave's Tech Service-PA

[duke]

hello,
joined the forum to hopefully gain some information on motor bike components. I built this Schwinn Corvette with one of the first 80cc motors that became available, "China Doll". The one thing I didn't care for was the 415 back to the rear wheel. I see there is a jack shaft kit offered by Don Grube.

 

[Sidewinder Jerry]

I have a shifter bike. The big question is do you need gears? Having gears won't make you have a higher top speed. It can give you a higher average speed in hill country because you can adjust the drive ratio to stay in the max hp rpm range.

These conditions should exist before considering the complexity of adding gears.

1) Being a large person (200+ lbs).
2) Steep gradients (20+% grade hills)
3) Low-powered engines (less than 3 hp)
4) Pulling/carrying heavy loads (200+ lbs).

If you don't need gears for a practical reason but simply want them, I recommend running your shift kit to a 3 or 5-speed IGH instead of installing a rear derailleur to a multi-speed cog system. This will eliminate cross-chaining and you can also use a 410 chain instead of a standard bicycle chain.

 

[duke]

I would like to try out that jack shaft set up, have a potential bike lined up. Would need to change over to a thumb shifter 6-speed.
I am 235lbs and that Schwinn went pretty well!
Having the option to run 6 gears on a simple Suntour, via the jack shaft, give me an advantage on inclines too.
Are you familiar with that grubee Jack shaft?

 

[Sidewinder Jerry]

I would like to try out that jack shaft set up, have a potential bike lined up. Would need to change over to a thumb shifter 6-speed.
I am 235lbs and that Schwinn went pretty well!
Having the option to run 6 gears on a simple Suntour, via the jack shaft, give me an advantage on inclines too.
Are you familiar with that grubee Jack shaft?

GruBee has a very good reputation. Since you plan to go with a 6-speed freewheel, change the stock axle to a cro-molly axle. The stock axle is prone to bending. I've found the Sram X4 to be the best rear Derailleur to use. However, you will need a Sram X3 shifter. A Suntour 7-speed 34-13 freewheel will give you a wider ratio range. As for a bicycle chain I use a Shimano HG72.

 

[duke]

I’ll have a slew of options at the shop, great place I frequent here in Chambersburg has an endless inventory. I will look at this road master but might not like the components.
The frame is ideal tho’
Prefer a mongoose Dolomite, the Jack shaft will just fit and allows for the wide tire by driving from the crank, however those can be expensive.
Making sure the GruBee “ Don” can put together a kit that’ll suit me, don’t want to push his patience tho’