Motorcycles - shaft to chain conversion?

[Commander_Chaos]

I have a half-built rat chopper that I'd like to finish this year. I was going to use one of my old SR500 engines but it's kinda small and slow for the size frame I'm using. My thought is to purchase a running 80's era street bike and cannibalize it but all of the ones on Craigslist in the sub-1000 dollar range are shaft drive. I particularly like the Virago engine.

I remember the XS-750 had a bevel gear as well as an aftermarket kit to change it to chain. Anybody ever done this? It seems like there must be an output shaft that's perpendicular to the centerline of the machine since that's how the crankshaft is oriented.

[psomero]

you're going to eat 20% of that extra power to gear losses

[Erich]

I can't speak to the Virago but I was looking into Kawasaki KX1400's awhile back They offered that motor in shaft and chain drive versions. The gear ratios inside differed but the shaft drive bevel bear and housing just bolted on over the output shaft of the chain drive shaft. So converting was a bolt on affair as long as you were ok with the gearing differences.

[Ian B]

Psomero, Erich,

As I understand it, he wants to go from shaft drive to chain drive, not the other way around.

It should be possible to replace the first bevel gear with a small sprocket. but some gearbox casing may need to be cut away to give clearance. The sprocket will have to be far enough outboard to clear the rear tyre.

Ian

[oxford]

I can't speak to the Virago but I was looking into Kawasaki KX1400's awhile back They offered that motor in shaft and chain drive versions. The gear ratios inside differed but the shaft drive bevel bear and housing just bolted on over the output shaft of the chain drive shaft. So converting was a bolt on affair as long as you were ok with the gearing differences.

This may or may not be a real problem. To the OP I would do a little homework and see what kind of ratios are in the trans and/or primary before doing a bunch of work in the conversion.

[Willy]

Lots of information on the Virago shaft to chain drive conversion if you do a quick Googloo.

[BCRider]

Psomero, Erich,

As I understand it, he wants to go from shaft drive to chain drive, not the other way around.

It should be possible to replace the first bevel gear with a small sprocket. but some gearbox casing may need to be cut away to give clearance. The sprocket will have to be far enough outboard to clear the rear tyre.

Ian

Early on there was also the XV920 that used the same engine as the early Virago but with a chain final drive. It had black fins like the engine in Willy's picture. And I'm pretty sure that even the early shaft drive Virago had all aluminium coloring. So I'm thinking that this is an XV920 engine. But of course that's a custom bike so anything is possible.

Looking at pictures of the Virago shaft drive engines it sure looks like the final drive portion of the cases is part of the bigger case. And that seems to be confirmed by a quick check for parts diagrams of the engine cases. So it's looking like it's not a practical swap. But another quick check did show that there's a few different Virago service manual PDF's that can be downloaded. Looking at the engine and gearbox sections should quickly figure out how practical such a mod would be.

If the engine choice is fairly optional why not go for some other options? For example, the Kawi 800 and later 900 Vtwin uses a chain final. Or later on a belt final. And then there's the current Yamaha Bolt V engine with belt final. And I'm sure that there are a fair number of others too. I didn't follow the cruisers that closely but I know there were a few options that did use chain or belt final drives.

[Commander_Chaos]

Lots of information on the Virago shaft to chain drive conversion if you do a quick Googloo.

I saw a lot of vague stuff but not much in the way of real technical info or conversion kits. A

Looking at the Virago parts diagrams I could find shows that there's a shaft and bevel gear coming out of the trans where a front sprocket would be. It's not clear whether the gear is on a spline or the shaft and gear are one piece.

Rather than tearing the trans apart and making something complicated I'd wait for a more suitable engine/bike to come along.

[754]

What do you have for machine tools right now. ... it maybe can be done with very little..

[QSIMDO]

I have a half-built rat chopper that I'd like to finish this year. I was going to use one of my old SR500 engines but it's kinda small and slow for the size frame I'm using. My thought is to purchase a running 80's era street bike and cannibalize it but all of the ones on Craigslist in the sub-1000 dollar range are shaft drive. I particularly like the Virago engine.

I remember the XS-750 had a bevel gear as well as an aftermarket kit to change it to chain. Anybody ever done this? It seems like there must be an output shaft that's perpendicular to the centerline of the machine since that's how the crankshaft is oriented.

EVERYTHING you need to know, or nearly, can be found right here;

https://www.youtube.com/watch?v=AYazK9dgNYI

Mike Waller's just done that and in a Commando frame.

[Willy]

Early on there was also the XV920 that used the same engine as the early Virago but with a chain final drive. It had black fins like the engine in Willy's picture. And I'm pretty sure that even the early shaft drive Virago had all aluminium coloring. So I'm thinking that this is an XV920 engine. But of course that's a custom bike so anything is possible.

Looking at pictures of the Virago shaft drive engines it sure looks like the final drive portion of the cases is part of the bigger case. And that seems to be confirmed by a quick check for parts diagrams of the engine cases. So it's looking like it's not a practical swap. But another quick check did show that there's a few different Virago service manual PDF's that can be downloaded. Looking at the engine and gearbox sections should quickly figure out how practical such a mod would be.

If the engine choice is fairly optional why not go for some other options? For example, the Kawi 800 and later 900 Vtwin uses a chain final. Or later on a belt final. And then there's the current Yamaha Bolt V engine with belt final. And I'm sure that there are a fair number of others too. I didn't follow the cruisers that closely but I know there were a few options that did use chain or belt final drives.

I believe you are correct. I had forgotten about the XV 920 Viragos much rarer than than 750s. And yes I also believe they did have black finished cylinders vs the aluminum finish of the 750s
As you say there are more viable options.

This from one shop possibly gearing up to do the conversion on the 750. You really have to be in love with your 750 Virago to eat this.

https://www.bigtwins.co/Conversion/

Don't expect this kit to be available right away. We are looking at machine work and metal treatment done across Orange County California (at three locations), with plans being drawn up and CNC programming set up in the Mid-West. Expect a thousand dollars exchange plus shipping and a month turn-around. Be delighted when it turns out to be a lot less and a lot faster. That's all I can tell you for now; work is in progress
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[d kirby]

I do not know a whole lot about the Yamaha XV 750 but I do know that there was an attempt to race that engine in AMA dirt track races back in the early 80's.
It never really met with much success.
The 750 version was both shaft and chain driven,and an oddity about that engine was it rotated backwards
It was a factory backed attempt by Kenny Roberts and Mert Lawill with Mike Kidd riding it.
I remember seeing it at the Syracuse Mile way back when. They were trying to compete with the H.D XR 750 which at that time was putting out about 80 Hp.

[Commander_Chaos]

What do you have for machine tools right now. ... it maybe can be done with very little..

I have a Millrite knee mill and a SB 13" lathe.

The 750 version was both shaft and chain driven,and an oddity about that engine was it rotated backwards

Yamaha has tended to favor engines that turn backwards in road racing because it counteracts some of the gyroscopic effect from the wheels. Honda tried it, too but gave it up because the amount of cancellation varied depending on the RPM of the wheels vs the RPM of the motor.

[754]

Well it sounds to me like you will need a spline adaptor , and a spline.. whig you can probably make with what you have.. but it's work..a lot of work.
having what you make heat treated for longivety is another matter..
or you may be able saw a coupler off or weld up the prices you need.
but probably cheaper to just buy a chain drive motor..