Topic: Intro / Right or wrong way to mount calipers?

[madmike750]

Hi all!  New to the forum from Pittsburgh.  I have always been into café racers and over the past few years, I have acquired a 73, 74, and 78 CB750s.  I first bought the 74 (which came with the 73 parts bike) 2 years ago.  It wasn’t running and basically a pile of crap but I am slowly turning it into my dream café bike.  I recently bought the 78 off of Craigslist for $300 running!  I really just discovered this forum and appreciate all of the help it has given me so far.  I hope to return the favor.  Onto the questions… 

1rst.  I am doing a dual disc conversion and even though I searched the exhaustive threads on the subject, I have yet to find the answer.  I would like to mount my calipers on the rear of the forks (see pic 1)as opposed to the front, which is the norm.  (see pic 2)
Can this be done?  I am ready to order my custom stainless lines but want to make sure that there are no unforeseen problems with my mounting solution.

2nd.  I’m sure Honda did it for a reason, but has anyone ever ground off that ugly ridge on the swingarm?  I was hoping to grind it off, weld the seam, then grind smooth for a nice box shape.  Will it destroy the structural integrity of the swingarm?  Any comments?

[MCRider]

Hi all!  New to the forum from Pittsburgh.  I have always been into café racers and over the past few years, I have acquired a 73, 74, and 78 CB750s.  I first bought the 74 (which came with the 73 parts bike) 2 years ago.  It wasn’t running and basically a pile of crap but I am slowly turning it into my dream café bike.  I recently bought the 78 off of Craigslist for $300 running!  I really just discovered this forum and appreciate all of the help it has given me so far.  I hope to return the favor.  Onto the questions… 

1rst.  I am doing a dual disc conversion and even though I searched the exhaustive threads on the subject, I have yet to find the answer.  I would like to mount my calipers on the rear of the forks (see pic 1)as opposed to the front, which is the norm.  (see pic 2)
Can this be done?  I am ready to order my custom stainless lines but want to make sure that there are no unforeseen problems with my mounting solution.

2nd.  I’m sure Honda did it for a reason, but has anyone ever ground off that ugly ridge on the swingarm?  I was hoping to grind it off, weld the seam, then grind smooth for a nice box shape.  Will it destroy the structural integrity of the swingarm?  Any comments?

I've run mine on the back for 25 years. Your frontend is newer than my K1, but I think close enough. Simply pull the forks and slide them back in backwards. Problems?
Rerun the brake lines.  Stock lines, even if stainless won't work, or would likely look funny. YOu need to make your own or go to a shop that makes them.
Drain plug is now on the highside. Deal with it.
Fender is on backwards. Drill out the rivets on the forkbrace/fender mounts, turn the fender around and bolt it back together with cute little stainless steel bolts and cap nuts. Or use rivets.
Wheel is in backwards. Drop it and turn it around. No problems.

Don't know about your other questions.

[markjenn]

The first disc brakes on motorcycles had calipers facing forward, but the industry convention quickly changed to placing them behind the forks.  Behind is considered superior because it places the weight of the caliper nearer the steering axis of the bike running through the triple clamp which reduces the rotational inertia of the entire front end.  The early bikes like the CB750 used a primitive pivoting brake carrier to provide for caliper centering and I suspect this assembly has quite a bit of flex.  With the first CB750 perhaps Honda thought it better to have this assembly in tension than compression.

Anyway, reversing the caliper location was commonly done with dual-disc conversions and if you can get the parts to swap around and line up, it is a good idea.

The swingarms on our bikes look like they are made of two stamped steel sections with a welded flange on inside and outside edges.  I'd be hesitant about grinding these flanges off - those flanges may carry a lot of load and without the flange, I doubt you'd have enough metal to get a good seam weld that would be nearly as strong.   But I'm not a welding expert.

- Mark

[bryanj]

Having converted a 500 before i had the option of 550 forks you can even run one in front and one behind but you do get some odd looks, also with an Italian Marving exhaust system on it i could bottom the forks enough that i had to go straight as the front fender went between the two centre pipes----interesting when howling into the Right hander at Glen Hellen and watching the IOM plod leap over the straw bale

[madmike750]

Thanks guys!  The top pic is my front end and having the parts rebuilt, drive plate modified, and front end assembled, I guess I just needed someone to tell me that its ok to do it this way.  I feel better about ordering custom lines.

MarkJenn, thanks for the bit of history. It just makes more sense to me to mount them behind the forks for compression even though im sure Honda engineers put them in front for a reason.

Anyone else have any comments about the swingarm? 

[754]

IMO by the time you did all they work(I assume you meant grind it off and add a plate) you are well on your way to the work done in building a new one or re-tubing one. Not really worth the effort,

There are other arms that fit in quite easy. less work

I guess I got used to the look of the 750 arm, athough I absolutey cant stand things like the lower tank seam on a cbx or the cheezy motor mounts.. man do those parts look cheap..

[cafe750]

Being that the cb750K swingarms are two stamped steel halves welded together, that ridge is what holds the whole thing together. I'd leave it alone.  As far as getting the calipers behind the fork legs, just drop the forks out of the trees, and swap the left for the right, and right for the left and the mounting ears will be where they have to be...

[madmike750]

754, what swingarms can I substitute? 

I have heard a 550 swingarm will fit but is shorter.  Is this correct?

[SOHC4 Cafe Racer Fan]

Check out Voxonda on the forum.  Rob makes sweet looking Dresda-like swingarms with the stock bushings.  The price is great, too.

[crazypj]

Having converted a 500 before i had the option of 550 forks you can even run one in front and one behind but you do get some odd looks, also with an Italian Marving exhaust system on it i could bottom the forks enough that i had to go straight as the front fender went between the two centre pipes----interesting when howling into the Right hander at Glen Hellen and watching the IOM plod leap over the straw bale

 I remember it well, the forks would bend as well as compress. (to answer the question, just do it and deal with taking forks off to change fork oil, its the proper way to do it.) I did mine in 1979 or 80, forget exactly when
Marving was not one of the worst for making 550's go in straight lines, that was the RC drag pipes but I think everyone I knew with 550 and dual discs had 'speed bumps' just above lower mudguard brace. I ended up fitting a GS1000 fiberglass copy mudguard, plus CB750 fork tubes and springs
I had an S&S exhaust (the British company), not USA S&S

[bert96]

Check out Voxonda on the forum.  Rob makes sweet looking Dresda-like swingarms with the stock bushings.  The price is great, too.

I can't find the thread,anybody does?

I would like to see that.

oh, and by the way(i don't want to hyjack) but any body know if a swingarm from a cb1100 fit on a cb750 k4?