Topic: Wheel conversion 78 F2 from comstars to retro spokes and rear hub.

[Warthog1959]

I have a 78 F2 I would prefer to have the older style spoked wheels with a rear hub brake. I look at the parts manual on line and the axles are the same part number. Can anybody tell me what I need to change to make this happen? Perhaps a K series triple tree and forks. Will the rear drum brake type wheel fit straight in. I am not concerned if I have to go down to one disc on the front although if anybody knows a way to keep the twin discs then that is all well and good. I have asked quite a few experts on this and they do seem a bit confused. But there has to be a way as it is only metal.

[Syscrush]

But there has to be a way as it is only metal.

That attitude will get you far!

Sorry, I don't have any concrete info/help/advice to give.

[754]

I offered to build a few front hubs, but no one stepped up.

 It appears that some DOHC 750 had a wire wheel, have not been able to tell, if bolt pattern is what you need..

 There is usually a way..

[hapakev]

The easiest way I have read is to get a gl1000 front end.  It has a spoked wheel with dual disk brakes and rotors on the rear mof the forks like a 78F.  The calipers appear to be the same as the 78 F also.  I have not tried this, but it is whats recommended.  Im not sure about the rear wheel.

[SWEETPEAUK]

I did this conversion for my F2, but it was years ago. But I remember that speedo drive on the hub had to be modded and discs were turned down to the same size as the f2's, I think the thickness was taken down as well, not sure. you have to add spacers to the back of the disc or caliper to get it all to line up. Don't know about the rear as I had a 16" CMA made,

[Don R]

The 75-76 f had a disc rear with a wire wheel. It might fit. If you go rear drum you may need a K for the swing arm, brake strut, and pedal linkage with frame mods. I would trade a K front end with a wire wheel for an F front end as would many others here.

[nobody]

GL1000 front end and a 75-76f rear end is going to be the easiest way to convert to spokes. Doesn't seem worth the time, money and effort to me so I won't be doing it.

[simon#42]

i was going to do this but then found a pair of dymags so changed my mind . bought a 750 f1 rear wheel hub which fitted fine as long as you use the f2 sprocket carrier [ which is wider than the f1 ]  not sure if the rim lines up ok as i only bought a hub . i think this is a very worthwhile mod , spoke wheels not only look better they weigh a lot less than the comstars [ i could not believe how heavy the back wheel was !! ]  a f1 or k front wheel was very close to fitting in the front but the disk was a different size [ the f2 disk has different fixing hole pattern so you would have to turn the k disk or disks down ], i dont think it would take alot to make it all work

[Old Scrambler]

'75-'77 GL1000 front end with wheel & tree..........K swingarm with 17" rear wheel from a '75-'76 750A.........shim the sprocket for best alignment..............This gets you aluminum rims on both ends.

Or.........restring an early GL1000 rear rim to a K hub.  The early GL brakes are the same as CB750.

[Warthog1959]

This is great stuff, giving me real food for thought. I have managed to get hold of a complete K wheel with hub, sprocket and tyre. For £150 only I have also sourced a GL1000 front end complete, which I am going to look at tomorrow.

I'm building a cafe and comstars look awfull in my opinion. I suppose they do not go convey an old school look, but the spokes definitely do.

I am UK based so a swap is not an easy option. Also I am back to single disk at the front, unless I do a conversion which is an equal amount of hard work I think.

I am still not sure why I woud need a K swing arm, because the axle for the F and the K is the same part number. But I'm sure I'll find out.

Keep the suggestions coming thank you.

[strawhouse]

I did the same thing to my 78F, But I had a 76F with wire wheels sitting in the back of my shop.  So I switced the front wheel and forks, everything went together fine.  The rear wheel I just need to switch the sprocket, I had to use the orginal 78F sproket.  Other than that it was straight forward and easy, took it out for a spin worked great and I have never switched it back.

[Thunder]

@ Strawhouse

I was looking into this as well,  if I'm reading right you changed the rear sprocket of the (75-76) to match the 78 front sprocket (different chain size?)

I heard there was an offset of some kind?
Did you have to make any kind of adapter etc?
Did the wheel slot into the 78 swing arm ok, or did you make up spacers?
Or did you  slot an entire 75-76 rear end (swing arm/wheel) in?

Thanks
Thor

[strawhouse]

The sprocket on the rear wheel off the 76 was different from the sprocket of the 78. ( the chain wouldnt fit )  So I switched the sprocket off of the 76 rim and put the original sprocket from the 78 rim onto the 76 rim.  Then the chain would fit as per normal.  I didnt have to make any spacers or switch the swing arm, the only thing that made this different from putting a stock 78 back tire back on was having to switch the sprocket.  Like I said I didnt research anything, I was bored, had some time on a sunny afternoon and thought those wheels would look way better on my 78!  Enjoy

[bucky katt]

well, i have a complete rear wheel and rotor from a 75 750f, spokes with a rotor on it. i'd be willing to sell it but i bet shipping will be a #$%* from south carolina

[jjlt80]

I'm planning on doing the conversion really soon as well. I have a 77 cb750f in which I'm going to convert the comstars to spokes. I purchased a 76 GL1000 front fork and rim. I'm hoping my front calipers will pop right on. I'll have to get a speedo as well. I'll be able to keep my top stem bearing the same while replacing the lower stem bearing with GL1000 bearing.

I'm a little worried doing the rear conversion. I purchased a 75 cb750f rim. People have been saying that the sproket is thinner making the swingarm narrower. I recently purchased a 76 cb750f swingarm that looks different from the 75. Do both rims/swingarms from 75 and 76 run the same width? I'll put my 77 sproket on the 75 rim if that's an easy fix. It seems like there are a lot people doing the conversion this year!

[eurban]

I'm planning on doing the conversion really soon as well. I have a 77 cb750f in which I'm going to convert the comstars to spokes. I purchased a 76 GL1000 front fork and rim. I'm hoping my front calipers will pop right on. I'll have to get a speedo as well. I'll be able to keep my top stem bearing the same while replacing the lower stem bearing with GL1000 bearing.

I'm a little worried doing the rear conversion. I purchased a 75 cb750f rim. People have been saying that the sproket is thinner making the swingarm narrower. I recently purchased a 76 cb750f swingarm that looks different from the 75. Do both rims/swingarms from 75 and 76 run the same width? I'll put my 77 sproket on the 75 rim if that's an easy fix. It seems like there are a lot people doing the conversion this year!

The GL caliper carrier is a different part for sure but I am not certain about the calipers themselves.  I doubt you will be able to directly bolt the F2 carrier to your new GL forks.  Basically you will probably need the GL carriers as a minimum and likely the calipers as well.  You do also know that you need the GL rotors since they are a different bolt pattern, diameter and offset than the F2 ones?
I also wouldn't try and reuse any bearings for the steering stem.  Bearings and races become matched over time and you won't likely be able to remove races without damaging them.  Simply get yourself a new tapered roller bearing kit and make an actual improvement in your front end rather than kludging something together.

[rebabal]

well, i have a complete rear wheel and rotor from a 75 750f, spokes with a rotor on it. i'd be willing to sell it but i bet shipping will be a #$%* from south carolina

Yo, I'm in SC and would be interested

Where about are you located?  I'm in Rock  Hill (near Charlotte, NC)

On a side note, I want to do the same thing.  I bought a 76K that has already been modified to a 78 front end for dual brakes and rear single disc.  I hate the comstar wheels and would be willing to sell the whole shabang to convert to spokes and a single disc.

SO, if anyone wants a 78 front end with dual brakes & rear comstar with brake, let me know - I want to go to spokes.

[jjlt80]

Thanks. I should look into getting a GL caliper carriers. My GL rim came with the rotors so I'm fine there. Also, thanks for the insight of the tapered roller bearing kit.