Author Topic: GL1000 to CB750 front end swap (Read 8999 times)

b1jackson · « **Reply #25 on:** May 08, 2018, 02:00:16 AM »

Is a 78 model GL a suitable donor for this swap a roo?

seanbarney41 · « **Reply #26 on:** May 08, 2018, 03:15:43 AM »

Quote from: b1jackson on May 08, 2018, 02:00:16 AM

Is a 78 model GL a suitable donor for this swap a roo?

as long as your good with running a comstar wheel...and even then, 77/78f front end is a better fit with even better brake options but would have to settle for 35mm fork tubes

b1jackson · « **Reply #27 on:** May 08, 2018, 03:30:19 AM »

And I'd need the rear comstar off the GL as well?

70CB750 · « **Reply #28 on:** May 08, 2018, 04:28:38 AM »

Quote from: b1jackson on May 08, 2018, 03:30:19 AM

And I'd need the rear comstar off the GL as well?

Only for the looks.

I married F2 wheels and fork with K3 frame. I am very happy with the result. Rear disc brake and brake pads all the same front and back.

http://forums.sohc4.net/index.php/topic,115305.msg1299318.html#msg1299318

b1jackson · « **Reply #29 on:** May 08, 2018, 04:41:36 AM »

Yeh, I'd want it to match. If I do this swap, it would be for a 75F.

Bankerdanny · « **Reply #30 on:** May 08, 2018, 08:37:47 AM »

Quote from: b1jackson on May 08, 2018, 03:30:19 AM

And I'd need the rear comstar off the GL as well?

The GL is shaft drive, the wheels won't work for our chain bikes.

The 77-78 750F uses the Comstar that matches the 78 GL, but it is a disk brake, so you need more than just the wheel to make that swap. I think that the rear wheel from an early 80's CB400 Hawk is the same Comstar style, but drum brake/chain drive, I don't know how wide it is though.

slikwilli420 · « **Reply #31 on:** May 08, 2018, 08:44:40 AM »

All this depends on how much fabrication you want to do. You can use the F2 forks with wire wheels, and will simply need to adapt rotors for the proper spacing. You could either adapt the 5 bolt rotors to your hub, or find some of the many 6 bolt rotors out there and space them properly. Lots of guys like the F2 forks for racing, but I liked the extra stiffness provided by bigger and slightly thicker fork tubes from the GL. Either way, all of this can work, just needs some thinking. The GL hoops can be used front and rear on an early F but will be 19/17 which isnt the best combo for performance. At that point, you could source a set of mag wheels or get some new 18" hoops front and rear and go from there. You can how I set my forks up for my Sportsman 750 race bike in my signature.

dusterdude · « **Reply #32 on:** May 08, 2018, 05:08:37 PM »

I skipped all the nonsense,so if its been covered my bad.the 1975/76 gl1000 front end is a direct bolt on.you can even use your front wheel.

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seanbarney41 · « **Reply #33 on:** May 08, 2018, 06:14:24 PM »

yeah Mark, I think its getting more difficult to source these front ends, especially for a low price.

b1jackson · « **Reply #34 on:** May 08, 2018, 06:19:59 PM »

Quote from: dusterdude on May 08, 2018, 05:08:37 PM

I skipped all the nonsense,so if its been covered my bad.the 1975/76 gl1000 front end is a direct bolt on.you can even use your front wheel.

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This is exactly what I wanted to hear. I'll eventually stumble upon an older wing but this 78 model is just too much hassle for me and outside my mechanical limits (plus comstars? Meh.). Great thread!

seanbarney41 · « **Reply #35 on:** May 08, 2018, 06:22:27 PM »

meh, I just checked ebay and I guess they are still fairly plentiful and reasonable priced. It is important to try and get the lowest mileage ones you can though, as slider bushing/rings are not replaceable on these.

seanbarney41 · « **Reply #36 on:** May 08, 2018, 06:23:26 PM »

Quote from: b1jackson on May 08, 2018, 06:19:59 PM

Quote from: dusterdude on May 08, 2018, 05:08:37 PM
I skipped all the nonsense,so if its been covered my bad.the 1975/76 gl1000 front end is a direct bolt on.you can even use your front wheel.

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This is exactly what I wanted to hear. I'll eventually stumble upon an older wing but this 78 model is just too much hassle for me and outside my mechanical limits (plus comstars? Meh.). Great thread!

I think the cut off is 77 though, so you are all good with 75-77 front ends

Bankerdanny · « **Reply #37 on:** May 09, 2018, 08:53:33 AM »

There are a couple vendors on EBay selling 75-77 front end parts relatively cheaply, but by the time you get the legs, trees, brake calipers, rotors (I believe the standard 750 rotor is different, you need the matching GL), brake line splitter, and master cylinder you are still probably in the $200 range including shipping. Not crazy expensive, but not cheap.

dusterdude · « **Reply #38 on:** May 09, 2018, 02:18:26 PM »

Yes,you would need rotors

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lowriderbud · « **Reply #39 on:** May 10, 2018, 07:06:41 AM »

I have an early model GL front end acquired through some trading. How can I tell what year it is? Are there markings or fittings that are unique to certain years. It has forks, sliders, trees, bearings, brake mounts (but no brakes), and factory fork brace.

I don't plan to modify my K4 or my '78 F, I am interested in finding it a new home when I find out what year it is.

Pictures on request.

Later, Bud...

seanbarney41 · « **Reply #40 on:** May 10, 2018, 09:31:30 AM »

The 78 and later are wider than the 75-77 but I don't know exact dimensions. Tough call visually without the calipers and or wheel. Never seen a factory fork brace that wasn't part of the fender

dusterdude · « **Reply #41 on:** May 10, 2018, 03:55:59 PM »

The 75/76 front end uses the same neck bearings the 750 uses.i would go to all balls.com and get the bearing id measurements and measure the stem you have.that will let you know what you're dealing with.

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seanbarney41 · « **Reply #42 on:** May 10, 2018, 04:00:22 PM »

Mark, I think steering bearings and stem are the same from 75 to 81? or so? Only 75-77 allow you to easily use the cb750k hub

RAFster122s · « **Reply #43 on:** May 10, 2018, 09:23:03 PM »

Buchanans can mate your hub to a 18" rear alum rim with custom spokes for about $100 if the rim is different than a stock rim... unless you want them to assemble and true and balance the wheel and that is more $. The front wheel is a source for a nice aluminum rim that is stock looking and much lighter than the stock steel. So, don't dismiss the GL.

The beefier look is an asthetic that can be accentuated or reduced based on the front end treatment. The racers will often make custom brackets to mate the Lockheed or Grimeca or other racing caliper. You can have a bracket made to mate the common Honda twin pot caliper which was used on many Hondas of the late 70s and into the late 80s. It can be used with a larger diameter rotor. The Yamaha rotors are used on some guy's bikes. But I think that is with a 750 hub, ask Scottly as he uses or used them on his Seeley Honda 750. I think Frank, 754, has used the Yamaha rotors too.
So many owners won't notice the change of calipers if it is similar to the late 750 look of bracket design.

You will get significant fork improvements in handling with a fork brace and a set of RaceTech gold valve emulators. So, if sticking with stock 750 forks you really need to consider going that route and having Jeff do that for you. You will not regret it.
Braided brake hoses make a great improvement in brake feel and performance by not having the lines expand when you actuate the brakes. The proper brake caliper to master cylinder ratio will give you the change from the wooden stock brake setup to one that gives you better brake feel and modulation possible. Jeff knows how to give you improved brakes within the constraint of the stock setup. Drilling the discs will give you better wet weather performance and better dust and gas evacuation for the gases and brake dust created during braking.

Price a good set of Borrani or Akront ?sp? Aluminum rims and you will recognize the value of the wider GL aluminum front rim.
Polish the rim while it is disassembled and it will look good on reassembly, maybe not brand new, but very nice looking rim, maybe nice enough you will smile everytime you see it knowing how much you saved . That is something I would enjoy seeing, even if I had the money to do it...

David

68grandprix · « **Reply #44 on:** May 11, 2018, 04:22:21 PM »

I installed a '77 GL1000 fork setup on my '75 CB750 about ten years ago. The '77 had a different steering stem, so I ground the weld, pressed it out, then pressed in and welded the CB stem in(apparently there was a mid-year change and some '77 GL stems might be the same). Worked fine. I also installed new seals, honed and rebuilt the calipers, and a couple years later installed tapered roller bearings for a cb. I have the stock GL springs and it handles fine, better than stock. I also just dropped the tubes in the trees to get my correct ride height. Speedo cable screwed right on also. I'm running an '80something CB dual disc master cylinder(square). Jim

68grandprix · « **Reply #45 on:** May 11, 2018, 04:24:47 PM »

I'm also running the 19" GL alloy-hooped spoke wheel. IIRC(it was a long time ago) even with two discs it was lighter than a stock 19" cb steel wheel with only one disc.

dusterdude · « **Reply #46 on:** May 11, 2018, 05:16:50 PM »

Quote from: seanbarney41 on May 10, 2018, 04:00:22 PM

Mark, I think steering bearings and stem are the same from 75 to 81? or so? Only 75-77 allow you to easily use the cb750k hub

Isnt the lower? Bearing different?

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seanbarney41 · « **Reply #47 on:** May 11, 2018, 07:44:06 PM »

Quote from: dusterdude on May 11, 2018, 05:16:50 PM

Quote from: seanbarney41 on May 10, 2018, 04:00:22 PM
Mark, I think steering bearings and stem are the same from 75 to 81? or so? Only 75-77 allow you to easily use the cb750k hub
Isnt the lower? Bearing different?

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could be but never heard of this

PeWe · « **Reply #48 on:** May 12, 2018, 02:16:06 AM »

I added a disc and caliper on my CB750K6. MC DSS aftermarket as well as both discs. Caliper from Yamiya that sold for right side mount.
I have front brakes now, before not.

dusterdude · « **Reply #49 on:** May 12, 2018, 04:06:15 PM »

Quote from: seanbarney41 on May 11, 2018, 07:44:06 PM

Quote from: dusterdude on May 11, 2018, 05:16:50 PM
Quote from: seanbarney41 on May 10, 2018, 04:00:22 PM
Mark, I think steering bearings and stem are the same from 75 to 81? or so? Only 75-77 allow you to easily use the cb750k hub
Isnt the lower? Bearing different?

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could be but never heard of this

Bears investigating

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Author Topic: GL1000 to CB750 front end swap (Read 8999 times)