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’

 

[Gordy]

I suggest you pull off those fenders

 

[duke]

Pull fenders off of what?

 

[Sidewinder Jerry]

Pull fenders off of what?

He's probably referring to the Schwinn Corvette. Unless fenders are reinforced they tend to become an accident failure waiting to happen.

 

[Gordy]

Yeah. I made the mistake of keeping them on my first bike and lost the rear fender. It wrapped up in the rear wheel at 35mph and mangled my wheel and frame. From everything I've read losing a rear fender is bad, but the front fender cam kill you.

 

[duke]

Oh! That first build I posted for reference, yeah, the fender I custom cut and reformed right where your thinking about. I actually had a close call and knew then it needed corrected.

 

[duke]

Follow-up Don Grube, GRU BEE. I exhausted their patience
So GRU BEE components are out altogether
Not sure I really want to do another build, “I should just enjoy my retirement and forget about it”
H’mmm

 

[Sidewinder Jerry]

Follow-up Don Grube, GRU BEE. I exhausted their patience
So GRU BEE components are out altogether
Not sure I really want to do another build, “I should just enjoy my retirement and forget about it”
H’mmm

A fat-tire shifter is one of the more difficult builds. You may want to try a simpler shifter build. It's also possible to use an IGH as a jackshaft transmission to power the left side of the rear wheel.

 

[duke]

Perhaps you’re right, do a cruiser build?
I have seen the predator 212cc with torque converter, but that went right to the rear wheel. Suppose I could do that and run factory gears independently.
Can a 212cc with a torque converter run to an axle shaft down to a chain ring on a cruiser frame I wonder

 

[Sidewinder Jerry]

Perhaps you’re right, do a cruiser build?
I have seen the predator 212cc with torque converter, but that went right to the rear wheel. Suppose I could do that and run factory gears independently.
Can a 212cc with a torque converter run to an axle shaft down to a chain ring on a cruiser frame I wonder

A 212 has a tremendous amount of torque. Way more than bicycle drive components can handle. I'd run a 10t on the CVT and a 60t on the left side rear wheel. This'll give you a reduction range of 18\1~6\1. On 26" wheels you'd have a level ground speed of 46 mph

 

[duke]

I’m glad to see you calculated ratios! Perhaps the Death. Row 79cc is better suited and I can get one of those kits.
Might be stretching it a bit on a 212 and a crash would hurt a lot!
Thank you, I will take note of that and apply it accordingly.
Gru Bee has a 5/8 shaft to upgrade the CVT,
that way the bike will free wheel. I was going get the Gru Bee transmission made for 79 right, was gonna change the one drive pulley to 3/4 for 212
Stay with Desth Row kit and less guess work, trial error, etc
Thank you very much!