Building 4stoke shift kit

[primusbike]

First off, hello. This forum keeps popping up in search results and have read some great stuff here. I have built 2 gas powered bikes. The first using a golden eagle plastic ring and completely custom engine mount. The second, current bike I have now, is a kit from staton.com Rear axle mounted 33cc subaru engine.

I want speeds. I also hate the reliability of gear clusters and derailers! My plan for providing gears is to buy an expensive 8 speed internally geared rear hub. I have seen the shift kit from sickbikes and that would be base for my next bike. Im going with the honda ghx50 for an engine.

Okay, now here where I NEED HELP.

The gears (gearbox) that initially reduces the speed of the engine. In the pictures of the shift kit installed with a 4 stroke engine, the engine has a "complete stage III" gearbox.

question, what gear ratio is that providing?

Can I use the 5:1 ratio belt transmission from bicycle engines.com with the shift kit?

 

[recumbentbill]

Welcome to the forum. I have a golden eagle[parts on the shelf] , had a staton[sold it] first in frame was grubee stage 111 with HS142 engine then the grubee 4g [honda version] which I sold. Finally went back to the stage 111 with shift kit plus sturmey archer 3 speed THEN I got sick of the HS142 engine and bit the bullet for a Honda GXH 50. Had to do a few mods[one more to go/ clutch engagement springs]. So far I'm really happy with the reliabilty and performace. For me 3 speeds is all I need.

 

[ocscully]

I too have the SBP 4-stroke Shift kit with the Honda GXH50 motor. I started out with the Grubee III Gearbox which provides 3.7:1 reduction and used the SBP 48t and 36t chain rings. I rode this set up for 7months and 6000+ miles. Back in October I switched to the Grubee 4G for Honda Drive which is the 5:1 reduction. With the extra reduction provided by the 4G unit I substituted a 44t chainring for the 48t to bring everything back to balance. Being able to fine tune the ratios relatively inexpensively is one of the beauties of SBP Kit. They have a variety of chainrings available and all are around $10.00 or less. Currently it seems that all vendors are Out of Stock on the Grubee 4G drives and Kits. You may find that when the come back in stock this Spring that they may not offer the 5:1 Reduction. Alot of folks seem to think that 5:1 is to much primary reduction. The Newer 4G drives seem to be most commonly found using the 80t pulley offering 4:1 reduction. Either one of these reduction can be easily adapted to the SBP Shift Kit.

ocscully

 

[primusbike]

I too have the SBP 4-stroke Shift kit with the Honda GXH50 motor. I started out with the Grubee III Gearbox which provides 3.7:1 reduction and used the SBP 48t and 36t chain rings. I rode this set up for 7months and 6000+ miles. Back in October I switched to the Grubee 4G for Honda Drive which is the 5:1 reduction. With the extra reduction provided by the 4G unit I substituted a 44t chainring for the 48t to bring everything back to balance. Being able to fine tune the ratios relatively inexpensively is one of the beauties of SBP Kit. They have a variety of chainrings available and all are around $10.00 or less. Currently it seems that all vendors are Out of Stock on the Grubee 4G drives and Kits. You may find that when the come back in stock this Spring that they may not offer the 5:1 Reduction. Alot of folks seem to think that 5:1 is to much primary reduction. The Newer 4G drives seem to be most commonly found using the 80t pulley offering 4:1 reduction. Either one of these reduction can be easily adapted to the SBP Shift Kit.

ocscully

Wow. That is exactly what I needed to know. Thank you. I would prefer a belt for initial reduction just because high speed belts are quieter than gears. Has anyone mounted a belt cog to the output shaft of a 4G? In other words, instead of a chain to transfer power from the 4G to the jackshaft, another belt? Im not sure how the sprocket is fastened to the end of the jackshaft, but surly a similar cog belt pulley could take its place...

 

[primusbike]

Also, has anyone ever modified the honda GHX50 4 stroke engine to have an electric starter?

 

[primusbike]

I guess I was overwhelmed to have my exact question answered so quickly and completely! I am full of questions and lay myself down to you guys and your knowledge.

another question: Do internally geared rear hubs work on frames built for a gear cluster? Are they different widths?