Topic: Comstar swap on a 77 CB750 SS

[chopstar]

Hi guys. This is my first post, and of course, it is a question.

Is it possible to swap out the Comstar mag wheels on a 1977 CB750 Super Sport with spoke wheels from an older CB750? I'm sure that the purists hate that idea, but I really prefer the spoke wheel look. I know that the front is dual disc and the rear a disc, but aside from those attributes, are they both the same dimensionally with respect to the axles and such?

A little about me: Located in the Mid-Michigan area. Fresh out of a divorce. I just picked up the 77 SS for a project to keep myself occupied. I'm hoping to do a complete resto, with just a few minor mods.

Thanks in advance.

Jeff (Chopstar)

[chopstar]

Guess I just answered my questions. Did a search real quick and found a few answers. I was hoping for an easy swap, but it does not seem to be the case. Any input is still appreciated. Thanks.

[Lumbee]

...Jeff, sorry about the divorce, but welcome to the board.  All the 77/78 750's run a slightly wider final drive, so for the rear wheel, a wheel from a 77 or 78K (which is spoke) should bolt right on.  Once its mounted you'll need to deal with the brakes.  I think (someone will correct me if I'm wrong) that the K models had a drum rear brake...which won't work as you have a disk brake in the rear.  The front should be a little easier...a 69-78 should mount OK, again the brakes will be the challenge.  You have dual disks now whereas the K's have single disks.  You could possibly use a K model front wheel with the accompaning brake set up from the same bike.

[kaceyf2]

 
hya there Bro, I did this conversion myself for exactly the same reasons as you want to!! I absolutely hate comstars for many reasons but mainly cleaning!!!!
here goes, I will take you through the front first then the rear! You have choices to make, mainly do you still want a twin disc set up on the front?
If you are not bothered it is slightly easier then if you are, but both are possible!
You will need fork lowers off a post 75 "k" series OR an F1. these use 35 mm fork stantions that are unbushed, they also have the mounting points for the calipers on BOTH legs.
This was for people that wanted a twin disc conversion for spoked wheels.
the calipers for the sohcf2 mount BEHIND the fork legs AND are wrongly spaced for a spoked wheels disc (whether single or twin) The spoked wheels disc/s are held on by SIX bolts and the F2's is held on by five! the f2's discs are set wider apart than on a cb750 k series twin disc conversion.
so, if you use a post 1975 k series or F1 fork lowers, that will let you run a cb750 k series front spoked wheel, get your self a k series caliper or f1 caliper and you have a single disc set up......get yourself  a caliper for the other side, AND six longer bolts to take it, and you have a twin disc set up on a spoked wheel on the front.........HOWEVER, you will also need the mudgaurd for those fork lowers! Your 76 f2 one wont fit anymore!

Now to the rear!  The cb750 F1 has a spoked rear wheel AND a single disc set up !!!! GREAT you may think I will throw that on!!!  and so you shall BUT...........
The brake caliper is exactly the same width as the f2, The wheel spacers are EXACTLY the same width as the F2 BUT when you put an F1 swingarm next to an F2 one on the floor , the F1 one is narrower!! so where is the extra bit GONE?? Answer... The sprocket carrier is narrower on an F1 than on an F2, from memory, i think i used the f1 swingarm in the end.
the tie bar for the caliper on the f1 and f2 are identical, so use whichever one you have!
I used the f1's caliper because  it has two pistons in it, whereas the f2 has just one, and it looks prettier, with all those grooves polished up its a loverly looking item.
Honda did a twin disc conversion for the K series that gave you a second caliper, caliper mount, another disc and six longer bolts,and a different master cylinder to handle it!     some people did their own and there are a lot still about, watch out though , the "second" front disc is actually different on a K series "twin disc conversion" as it is scalloped out for the speedo drive to not foul!
I have a period twin disc conversion for a K series Or f1 spoked wheel should you need it, but i am in the UK .       
 Hope this helps!

[theunrulychef]

Damn, kaceyf2, I wish you were around when I was asking about this a few months back.  I've been collecting Goldwing front end parts to throw on my F2.  Sounds like I could have been done by now if I went with your plan.

Here's the route I was directed to by people who have done it before:  Whole GW 1000 front end - wheel & rotors, forks, trees, and brakes (gonna check if F2 brakes work before I buy the GW ones).  The whole thing is supposed to bung right up to the 750 head.  I've also got some tapered steering bearings for the F2, but I've heard that people have had luck using the top bearing from the F2, and bottom bearing from a GW kit.

About the rear.  It looks as though the F2 sprocket carrier takes up the extra room, so using the F1 wheel w/ the F2 carrier & brake - will this not work because of the wheel offset?  If so, I'll have to get myself an F1 swingarm (damnit).  Also, I don't suppose you threw on a 16" rim like I'm planning.  Someone scared the bejesus out of me when they said that there's clearance issues for a 16" rim & disc brakes.

Either way, I think I may be riding with comstars until next winter (or until after my wedding in August).  The great weather & total lack of funds is really making me want to just put the f#$er back together asap so I can get riding again.

Thanks,
-Jay in Philly