Bike engines and gearboxes

James_1 · 3 June 08, 16:56

I have heard that the engine speed on a bike is reduced before it goes into the gearbox. Is this correct? Also, how much is it reduced? I am trying to work out what needs to be done to fit a bike engine in a car and what FD I would need.
Thanks

CX650 · 3 June 08, 19:09

Quote:

Originally Posted by James_1

I have heard that the engine speed on a bike is reduced before it goes into the gearbox. Is this correct? Also, how much is it reduced? I am trying to work out what needs to be done to fit a bike engine in a car and what FD I would need.
Thanks

The primary drive from crank output to clutch input usually has different sized sprockets. Precise details of tooth ratios are not within my personal knowledge. Not all bikes are configured the same, e.g. a BMW K100 runs a Borg and Beck single plate clutch attached to the flywheel in similar fashion to cars.

Pizzaman · 3 June 08, 19:23

Why so surprised...
the Mini also has a transfer-gear system.

Roger · 4 June 08, 15:05

Hi James - the reduction ratio is very often listed in the spec sheets (don't confuse with the final drive ratio). Get a Haynes manual for the bike I am 99% sure it will be in there. I have a Suzuki workshop manual (factory one - not Haynes) and it's definately in there.

I think changing the primary ratio would likely be a hassle and much easier to focus on the final drive (maybe you were? and were only thinking of the numbers?).

The final drive ratio is easy to calculate - count the teeth on the sprockets!

I don't think you need to know the primary ratio - With the final drive ratio, the tyre rolling radius and knowledge of speed/revs in top gear it will be easy to work out what gearing you want.

In pretty simplistic terms - putting a bike engine into a car the final gearing is immediately lowered by having smaller diameter tyres.

I would guess that you probably are looking at a chain drive to a sprocket operating a differential. Changing the sprocket sizes is pretty easy. Many people will make bespoke ones.

Having lower gearing will probably help a bike engined car - most bikes with the type of motor that will push a car along are probably geared well north of 160mph. The car with it's greater mass and greater frontal area will probably need lower gearing to help accleration and will probably struggle with the upper reaches of top speed.

Loads of people do final drives for bike engined cars - a quick google will probably get you loads of data.

James_1 · 5 June 08, 18:10

Thank you very much Roger, I really appreciate that.

Pizzaman · 5 June 08, 18:55

Are you looking at a ExtreMini-build?

3 June 08, 16:56	#1
James_1 Uploader Join Date: Oct 2006 Location: Kent, UK Age: 21	Bike engines and gearboxes I have heard that the engine speed on a bike is reduced before it goes into the gearbox. Is this correct? Also, how much is it reduced? I am trying to work out what needs to be done to fit a bike engine in a car and what FD I would need. Thanks

3 June 08, 19:23	#3
Pizzaman Minifreak & Muscleman Join Date: Feb 2007 Location: Groningen Centre of the Universe	Why so surprised... the Mini also has a transfer-gear system.

4 June 08, 15:05	#4
Roger TT/3 Join Date: May 2003 Location: England Age: 54	Hi James - the reduction ratio is very often listed in the spec sheets (don't confuse with the final drive ratio). Get a Haynes manual for the bike I am 99% sure it will be in there. I have a Suzuki workshop manual (factory one - not Haynes) and it's definately in there. I think changing the primary ratio would likely be a hassle and much easier to focus on the final drive (maybe you were? and were only thinking of the numbers?). The final drive ratio is easy to calculate - count the teeth on the sprockets! I don't think you need to know the primary ratio - With the final drive ratio, the tyre rolling radius and knowledge of speed/revs in top gear it will be easy to work out what gearing you want. In pretty simplistic terms - putting a bike engine into a car the final gearing is immediately lowered by having smaller diameter tyres. I would guess that you probably are looking at a chain drive to a sprocket operating a differential. Changing the sprocket sizes is pretty easy. Many people will make bespoke ones. Having lower gearing will probably help a bike engined car - most bikes with the type of motor that will push a car along are probably geared well north of 160mph. The car with it's greater mass and greater frontal area will probably need lower gearing to help accleration and will probably struggle with the upper reaches of top speed. Loads of people do final drives for bike engined cars - a quick google will probably get you loads of data.

5 June 08, 18:10	#5
James_1 Uploader Join Date: Oct 2006 Location: Kent, UK Age: 21	Thank you very much Roger, I really appreciate that.

5 June 08, 18:55	#6
Pizzaman Minifreak & Muscleman Join Date: Feb 2007 Location: Groningen Centre of the Universe	Are you looking at a ExtreMini-build?