Topic: Belt Drive Conversion. Yes I did search. :)

[754]

Swingarm is the minor issue, once you can get the belt & front sprocket on, the rest is simple..

[Terry in Australia]

If you go back into the Greenspun archives, you'll see that this topic was discussed ad infinitum several years ago, and just like this time around, nothing came of it. Measurements were taken, discussion went for quite a while, but in the end we accepted that unless you want to run a belt the width of a chain (and obviously only a fraction of the strength required) you're just pisssing in the wind.

There are plenty of folk here who'd love a belt drive, but no-one here with the resources, (or the inclination) to construct something that's actually gonna work as good as, or better than a chain on a SOHC4 without major mods to the frame. 

What I find hilarious is that Anyone here over 20 will know that many types of belt drive have been tried over the 100 years or so that Motorcycles have been around, but for some reason most manufacturers remain loyal to the humble chain. 

To target Franks jibe regarding the magneto versus electronic ignition comparison, in fact the first motorcycle was belt drive, so he's got it bass ackwards. Cheers, Terry.

[Soos]

no one said anything about major mods....
I could easily see swingarm, case cover and frame having issues with using a belt drive.
Besides the obvious problems of the belt driven gear mounting, a custom output shaft replacement would almost be necessary for a nice clean setup.
Or at least a custom mating to the slined shaft for a close tolerance fit.

Overall it would be quite a feat.
If I come across the bits for dirt cheap, I will be looking at the possibilities. I have a rigid frame i've been thinking about doing.   
I already have most of the parts, just need $ and time, and i'm out of both lately.
That project is in-line after getting my 'lil bagger 650 road legal.

l8r

[754]

Off the top of my head,
I took a hard look at this a few months back & am going by memory..

The cases can be modified to give more room, not easy but not a real bunch harder than a chain busted case repair.. there is room to be had.

Yes it did look like frame would eventually touch, but no bigger mods than add a hardtail if front stretching a frame.

The belt will probably have to be installed with it on the pulley and angled so it is heading to the rightside of the bike as it gets slid in., so that means swingarm & wheel removal. I think some are thinking it will be slid in straight, like most bikes.

Belts have already proven themselves, comparing them to early other belts is not a fair comparison.

Yes it would take some work, But if compared to say building a frame from scratch for a 4, it is way less work than that.

[Soos]

It's things like this that make me try.... no one's done it.
why not?



hahaha... i seriously think my brain hates my wallet sometimes.....

l8r

[Gregorymoto]

I would have to say yes it could be accomplished, bla bla bla, and if one did they would have some major bragging rights and a cool factor of 100%. O yes i would buy you a beer and wave at you every every time i saw you on the road.
But.... for the time and money, i would spend it building a solid motor with an O ring drive chain.

[kpier883]

I think it is worthwhile to revisit these ideas from time to time; unlike a previous post that dismissed the whole thing.

As technology changes, things that once were not practical may become practical.  Kevlar reinforced belts and other advances certainly could change the width that a belt would need to be in order to be strong enough for a given application.  I am not going to kid myself or you guys and pretend that I have the resources to go out and do this to my 750, but I still think it is a worthwhile discussion, and who knows, down the road a few years, or on another bike that is easier to fit...

To me, this has been one of the more interesting threads lately.

[754]

Still no one with KZ 400 info?? we need beltwidth too.

I think 1inch is plenty, works on a sporty.

Now back to weight, the 11+ lbs for a front is not accurate.

I measured a Harley one today which is about 1.5 wide.. all steel. center is cut out that is about 2.7 dia by .55 minus the spline hole...it weighed about 4 lbs, and is about 3.5 or bigger.

The 750 one wont be bigger than 3 inch, probably around 2.7ish.

Now would be a good time for someone to post the HD belt display. They take this to the big shows, a metal frame and hanging from the framework is an ElectraGlide, fully dressed. The bike is held up  a few feet off the ground by a drive belt!


Btw, they slit the drivebelt lengthwise... that is the belt is about 5/8 wide!

[kpier883]

I don't have sizes on the KZ400, but this picture might help:

[754]

If rim size is known (probably 18), should be able to scale off the pic... width would be nice to know. looks like c-c may be close..

 And I wont have to follow that girl on that KZ around town anymore, think she is cared to stop when she keeps seeing my car behind her..

[kpier883]

Here is the link to the page where I saw this (KZ Twins).

http://www.armbell.com/forum/viewtopic.php?t=1685&mforum=kz400

There are more pictures.  There is one with a close up of the rear wheel and sprocket, but I can't make out the size of the tire.

[cbass*gxc]

It looks like the rear sprocket would be cake to make.  The front one looks to be a little harder.   

[kpier883]

Here is a link to a guy that tried to use Buell parts to make his VFR belt drive and came up a little short. 

http://www.vfrdiscussion.com/forum/index.php?showtopic=39497&st=0&start=0

A sample of what you will find:

[754]

I read the VFR story,
The only real problem he is left with is swingarm length/ adjustment. None of which would be a big problem on the CB750.

I can maybe see a solution to his problem, we should get a hold of him or direct him to here as he is pretty knowledgable on this topic.

Solutions to fix his,

Maybe swingarm pivot could be moved  in an eccentric way(dont know what they run, but I suspect bearings so it may be difficult)

Machine a new eccentric carrier for the axle moving it to the outer edge of circle, ie just breaking through.
or
Failing that, bore out the end of swingarm, moving the circle rearward several mm,s..then build new eccentric (bigger dia)with axle hole to the edge!

He only needs 3mm, I think he can get it the way I mentioned..

[Soos]

I agree.
With the VFR build he tried to do, i would personally go for the eccentric, or just lenthen the swingarm.
It's a bit of work.... But if you are gonna do it, may as well do it right..

l8r

[754]

I think on his swingarm, modding it would involve re heat-treating..

[1080]

I think trying to fitting the CB750's is a good idea, and I think it may possible.

754 ask me to post these photos ( Taken at Red Deer bike show ).

[754]

That bike is hanging from a Blast belt, it is the skinniest one..

 

just in case you had doubts of the strength of them..

[kpier883]

I know this is an old thread, but it is also the best one on this site for the belt conversion information.  Here is a picture of a 2010 Triumph belt system.  I think it is based on a Gates GT or GT2 style belt.  A rough count leads me to a count of about 172 or so teeth.  Browsing around the Gates site, I find a 180 tooth 14 mm pitch belt that might be this one.

The gearing would appear to be around 70:30 which is way off for our bikes.  I don't think it would pull top gear.  However, if Gates or someone had other sprockets it might work out. 

When I try to estimate center to center distance for the sprockets in this pic, it seems to me to exceed 36", but I may not have that right.  I worked off the 14mm pitch and the rough count of teeth in the belt.  That seems like a really long distance to me...

Anyway, the BMW F800 is belt drive too.  Some of these new applications may hold promise with respect to belt length etc.

[13bravo]

Yeah I know it's a dead horse, but here are some rough measurements from my 83 Kz440 LTD.
Belt is 1 1/4" wide
Front Pulley diameter to outside ribs is approximately 4 1/2"
Rear pulley to outside ribs is 11 7/8"
Center to Center of the pulleys are 23"
Outside to outside distance is 32"
Inside to Inside distance is 15"
Bolt pattern of rear pulley is approx. 2 5/8" Bolts are also a smaller diameter than Honda.
All measurements are an approximation as the bike is still mostly together.

[Terry in Australia]

Well since this thread started (and I note that no-one actually converted their CB750 to belt drive, what a surprise..........) I've bought a 1994 Harley XLH1200 with belt drive, and it works fine. Interestingly though, lots of Sporty owners are converting their belt drives to chain drive so they can run wider tires, alter the gearing or after increasing the engine's performance. Cheers, Terry.

[HondaMan]

When Gates Rubber was testing the belt drive (and creating them for H-D and Kawi), I worked with the R&D lab that used to then be here in Denver, building test machines to try to destroy those tough belts. They built several H-D bikes' test sprocket sets, several Kawi, 2 Suzy, and 2 sets for CB750 K3 and K5 Honda (the latter because 2 of the guys in the testlab office rode them). The only bikes to wear out the belts were the Hondas. But, it wasn't for power reasons: the issue was the front (counter) sprocket had to be made in 2 pieces to be able to install it with engine in the frame, and being aluminum they wore on each half enough to make them egg-shaped in fairly low miles. The H-D and Kawi bikes were a huge success (as we all know today), but their work on the Hondas was discontinued for the sprocket problem. Naturally, I wanted to volunteer my K2 to the tests, but they would not make me some sprockets, so I never got to actually put a set on my bike.

The testing machines were fun to make, though!

[Terry in Australia]

How wide were the belts Mark? Cheers, Terry.

[scottly]

I once drove past a Harley parked at the side of the highway, with the rider holding up at arm's length what first appeared to be a snake, with a puzzled look on his face. It didn't occur to me until a mile later that he was holding a broken drive belt, wondering WTF he was going to do. I have since seen emergency replacement belts; sort of a tongue-and-groove joint, with steel roll-pins inserted through holes through the teeth. 

[754]

That was the original emergency replacement belt, it was like a finger joint in wood...ie a vee fitting inside another vee. I believe they were fastened with long setscrews.
 Not much demand and not much breakage , so folks stopped worrying about them.