Topic: Belt Drive

[hcritz]

Morning Folks..
Just wondering if anyone had thought about changing over to a belt drive.
I haven't taken any measurements...my 77 uses a 630 chain...so there may be enough room there.
I like the idea of the quite and no mess/maint. of the belt.
Any thoughts???

[Geeto67]

Morning Folks..
Just wondering if anyone had thought about changing over to a belt drive.
I haven't taken any measurements...my 77 uses a 630 chain...so there may be enough room there.
I like the idea of the quite and no mess/maint. of the belt.
Any thoughts???

I don't see how it would be hard to do - there are plenty fo conversions from belt to chain for HDs.

There are companies that machine belt drive wheels for harleys out of billet - I'm sure it would be no problem to buy one undrilled or have one drilled to the cb750's bolt pattern. The only issue is what size since there really isn't much clearance for a belt wheel where the motor sprocket goes (and you would probably have to run without a cover. Harley sells a thin belt for use on their older bikes (it is part of a "wide tire" conversion kit to put za 150/160 where a 130 was previously) so you probably want that belt size.

For the expense of it I don't understand why you would want to do it? Chains are much more efficient and if you think belts don't need service, ask any HD dealer how many belts they change that have holes in them due to road debris.

[hcritz]

Hey Geeto...
I need to look and see what belt widths are available and take some measurement at the front sprocket and see what's there.
The 77s-78s I think have more room.  I don't think there is a strength issue with the belts...a big HD would put a lot more torque on one than a 750 would for sure! There may be issues with the geometry as the swingarms moves through it's arc...I know the chain tightens up some from being on the stand to when I'm sitting on it. Might require a spring loaded tensioner on the bottom run to keep constant tension.
I have though about just doing the 530 conversion...the 630 is just noisy as Hell. I sometimes ride long distances...and hate having to take some sort of lube to keep the chain happy. And it makes a bit of a mess on the rear wheel too.
I wasn't aware that they had much trouble with the belts...most of the folks I have talked with say they have run BIG numbers of miles with NO problems.

[Bodi]

You can go a long distance on pavement with a belt drive, but gravel roads are trouble. When a stone gets between the belt and pulley the belt cords break because there's no slack and the belt resists stretching quite strongly. Hopefully the belt just gets a hole or tears a bit but they can and do completely snap. A rock in a chain isn't recommended but they generally pass through with little or no damage because of the normal slack in a chain, and only small rocks can balance on a 1/2" wide chain. The wide belt can catch pretty big stones. I have seen a picture of a stone sweeper mounted on a Harley swingarm that pushes any foreign objects off the belt.
You would probably have trouble with the Honda swingarm geometry because belts have very little tolerance for changing tension. The belt will skip when slightly slack. Harley has obviously designed their factory frames for belts, and a hardtail chopper won't have any problem.

[hcritz]

Hey Bodi...
Thanks...I try to avoid gravel regardless...I have a KX500 for that purpose!<G>
500 lbs of top heavy street bike is not a good thing on gravel!
I'm pretty sure that there would have to be a tensioner on the bottom of the swingarm to maintain propper tension...
For truly proper tension without on the swingarm would have to pivot at the centerline of the front sprocket...not the situation we have on our bikes, but a simple spring loaded tensioner like used on the serpentine belts on most cars today would probably do the trick...
I'm just doing some brainstorming...the belts seem to be quiet, clean and maintenance free...

[Geeto67]

Hey Bodi...
Thanks...I try to avoid gravel regardless...I have a KX500 for that purpose!<G>
500 lbs of top heavy street bike is not a good thing on gravel!
I'm pretty sure that there would have to be a tensioner on the bottom of the swingarm to maintain propper tension...
For truly proper tension without on the swingarm would have to pivot at the centerline of the front sprocket...not the situation we have on our bikes, but a simple spring loaded tensioner like used on the serpentine belts on most cars today would probably do the trick...
I'm just doing some brainstorming...the belts seem to be quiet, clean and maintenance free...

buell's use the same sort of tensioners. Cycle excahnge also sells a chain tensioner that uses a skateboard wheel. easily enough procured.

[hcritz]

My 77 is going to get a complete restore this winter...and I'll probably keep it totally stock. It's a really nice original...had 10,000 miles when I got it last year. It's not a museum piece...but a very nice garage kept bike...with no mods made to it by the SPO.
I'll probably just do the 530 conversion on it.
I think I have procured 5 or 6 other 750s of various years and condition...May try to make one of them into a fun test bed...maybe a retro racer or something that I can modify and not feel guilty! It would nice to have a bike to try Ideas on...

[mrbreeze]

I used to work with a guy in Wyoming that bought a brand new 883 Sportster. He got the gravel in the belt treatment before he had 1000 miles on the clock. It punched a little hole right in the middle of the belt which promptly became a tear. Other than that,belts are great and pretty much trouble free.

[Bodain]

Belts are fine on low HP machines... Old Honda's and Harley's.

You will never see a belt on a motoGP machine. The belt would need to be 18" wide to transfer the power.