1971 Honda CB750 K1 - Can anyone ID these forks and wheels?

[Yamahawk]

Hi All,
   Recently acquired a 1971 CB750 K1, and it has a set of ComStar wheels and forks off of a different model CB750. I am thinking perhaps an early 80's CB750 DOHC, but would value any information about them. It looks like he swapped the whole front end, but it still has the handlebar top clamp with the idiot lights in it. I am not sure if he swapped the rear fender, also. I appreciate any input you may have on this bike. The ignition switch was 'butchered' into a keyed automotive type switch mounted behind the cylinders, too. Thanks!
Charlie

[K2-K6]

Looks an odd mix of parts and I can't quite get enough resolution to see front caliper well.

Forks caliper and disc look something like original but with a Comstar that looks as you say like first iteration of the twin cam 750. If you give a straight shot of just front wheel caliper, forks and mudguard from bike's left it may let others see more detail.

Rear looks like a 17 inch which we didn't see on that same bike over here,  chainguard looks like SOHC 750 F2 of 1977 vintage.

[Yamahawk]

It IS a mixture of parts, even the seat isn't stock. The rear wheel is a 17" and front is 19", glad the rear is 17", better tires available. I will go out in a bit and take a better picture of the front wheel/caliper/rotor. I'm thinking he bolted on a complete front end from an F2 or a CB750 Custom, as front fender also resembles later models... Thanks!
Charlie

[K2-K6]

The first Comstar wheel fitted 750s that ive seen use a different lower fork tube with a prominent cast ridge down front and rear,  also looks like you've got the swinging pivot caliper as original type and not used on F2 onwards.

Some of the others on here are better able to identify if the caliper is from the original bike so those extra pictures will help with that.

[Bryanj]

Front caliper is NOT f2, its a rear mixup and god knows where the bits came from, rear 17 inch could be K7/8

[neilg]

Not K7/8 as they were spoked wheels.The front wheel could be F2 not a DOHC as they did not have the black plastic bits on the spokes which were also ribbed and polished. My guess is they are from a late 750 Hondamatic the last lot had comstars and the headlamp brackets also look the same along with the badge on the bottom yoke.

As in    https://www.cmsnl.com/honda-cb750a-750-hondamatic-1978-usa_model7237/partslist/

[Rob62]

CB650?

[Tomb]

Is the seat not a 400/4 seat that's been hacked?

[K2-K6]

Rob62,  I don't think the 650 would take tye chain from a 750. Looks similar though doesn't it.

Neilg,  that looks closest I think. It's got that odd combination of old type forks with swinging caliper and Comstar wheels which I can't remember anywhere else.

That would make it less of a hybrid I guess if it's just the rolling bits grafted onto a K1 as at least the brakes,  wheels forks etc have been engineered to run together as a complete set.

[Green1]

The K1 should have the idiot lights in the clocks and a rhino horn top yoke. Looks like you have k2 onwards idiot lights.
The clocks don't look wright and the headlight looks like its of a Hondamatic.

[Bryanj]

Looking in the ID book the front end looks exactly like a 78 hondamatic even to the plastic bits at the rim/spoke join and the rear looks same as well but not sure what tyre size was on those as they never came to UK officially

[JamesH]

Just adding to the above, the clocks looks very similar to my ‘68 CL450. Also looks like a later K4 onwards cylinder head has been fitted? Maybe you have some other goodies in the motor?

James

[Yamahawk]

Hi All,
  I have taken more pics of the front end, here they are! I believe it is a stock set of front forks, with a triple tree of unknown year, and the front wheel off of perhaps a CB750A, along with the rear. The seat is not stock so it could be the 400 seat. I have a 72-76 seat coming, with the proper hinges and I will move the 'hook' latch over from this seat. I got the bike running rather well, had to clean the bleed hole in the master cylinder to free the front brake from sticking, and now it works well, I noticed that the right fork tube has mounts for a second caliper, and the ComStar has a mount for the second rotor, to convert it to dual disk brakes!
The instruments are not the stock speedometer, but not sure about the tach. I replaced the tach cable, as they had a square drive cable where it inserts into the head, and it is supposed to be the split mount cable end. Now the tach works well!
Here are some more pics!
Charlie

[Yamahawk]

Nelig.
   The CB750A did have this type of caliper also, and I am thinking the front end is off of this model of CB750A. That would explain the ComStar wheels, etc. I know there is at least 3 types of parts fitted onto this bike, so it will be a puzzle to sort out.
Here is a pic of the headlight area also!

[neilg]

How about a pair of F2 forks and brakes. The discs will also have to be F2 as they have a smaller diameter, though check the number of mounting bolts before you go ahead as I think the F2 has one bolt less than the K's, or is it one more...not sure but I have messed about with similar swop. I used an F1 wheel and ended up having the discs machined down as F2's didn't fit the hub. Gawd knows what pattern the 750A has. Interesting stuff.