Workingman's CB750 seat fitment and frame modications

Here's what the stock tail section on the CB750 looks like - grab rail, tool box and a brake light that can also be used to send semaphore signals between fleets.

The owner was after a seat that was a little funkier than stock, but still comfortable as the bike was his everyday rider. We sourced a shorter unit that looks pretty good, but the frame has to be modified fairly extensively for it to fit.

That's us getting enthusiastic with a red marker - that's all the bits that have to go. Here's the rear loop bend and welded in place, ready for paint.

Now at this stage we'd ordinarily like to take everything out and 2 Pac or powdercoat the frame but as the customer wanted a bike that he would ride every day and 'never, ever clean' it was hardly worthwhile. But here's the seat in place...

Perfect. We also added a neat little brake light and some indicators but, er, we forgot to take pictures. Sorry about that. When you're on a roll, you know?

While we were there we also cut and folded that aluminium sidecover. As with the tank there's no polishing there - just the fold and cut marks cleaned up.

Workingman's CB750 Tank

Here's a tank swap we did some time ago.

The bike is a late 70's CB750 and the tank is an aftermarket aluminium number designed for the SR400. We cut the bottom out of it and fitted a new tunnel, and moved the fuel tap over to the left hand side.

It's now gravity fed rather than vacuum. Slots in quite nicely.

And this is my favorite bit - we fabbed up some new mounts on the tank so it can bolt down to the bike firmly - the tabs allow the seat, which is also an aftermarket item, to lock surely in place.

The black CB750 all finished.

Here's the completed black CB750...

And some more detailed shots. The rearsets are a generic type and a backing plate had to be made from a 8mm plate of alloy, cut down to fit. The one plate also mounts the rear brake and exhaust to keep things simple and looking light.

A bank of the CR carbs. With the 865 kit on board, heavy clutch kit and with a proper exhaust the bike should run a lot better now than it did before.

That's a Joker Machine CNC'd top triple clamp. Bolted up nicely. I think a cast type might work a little better but to be fair it is an 80s CB750 so it makes sense. The speedo his a generic Posh unit or something like that and the bracket was made by us. It was drilled and finished for a row of idiot lights but after pairing down all the electrics it turns out that the bike can run without them.

Small headlight. The instruments, which are only just visible here have been chromed. It has a twin disc front set up and runs two brake lines the whole way rather than using a splitter box. The brake lines at the front and rear are stainless Goodridges.

The new exhaust system we fitted was okay, with the exception of the muffler. So we cut off around 8 or 9 inches and looked around the workshop for something that would suit. We scavenged this off our Bimota. 

And there you have it - a nice clean and simple CB750 cafe racer.

Some of the 'easier' things that we do.

And here's some of the more straightforward things that we did to the black CB750. Firstly, the ignition was moved to the front and tucked way under the tank.

Heavy-duty clutch kit installed.

A 'Dyna S' system was fitted from the pickups through to the brain. It ended up being a bit of a tricky job - while they can build great coils and pickups their control units take a bit of effort to get working correctly.

And a bank of CR carbs were fitted to make sure it breathes correctly.

Looking good so far.

Black CB750 - Making the seat and surrounds.

Here's a 1982 CB750 that we worked on a while back.

So first up, a little information about the seat, which was purchased from 'Benjie's Cafe Racer' in the US. It was apparently a straight bolt-on job but when it arrived it was twisted and bent out of shape and appeared to be fibreglass mixed with talc. We ended up spending 10-12 hours just trying to make the thing fit. Constant cutting and reshaping until we managed to make it work. In retrospect we probably should have cut our losses and just made a mold of the seat and started from scratch. It would have been quicker.

So after some altering of the seat the frame was cut and a new loop added. When this was done the seat matched up neatly...

There was more work to be done underneath the seat. The battery goes in the rear hump...

In that last photo you can see the beginnings of the work that we did under the seat. Brackets were made and stainless steel mesh was fitted to allow cool air to flow around the electronics. Other stainless plates were fitted and polished.

 And a plate was fitted in lieu of a fender. Small tabs welded up for this. Dry fitting it here to make sure all the screws were lined up correctly.

We did some more work which we'll outline in another blog post shortly. But in the meantime here's how the seat and rear frame looks at the moment. We think it looks pretty neat - especially given the quality of the item we had to work with in the first place! We painted the tank and seat in 2 pack gloss black.

Have you thrown some money on a part that needs some massaging to fit? Contact us for a chat to see if we can, cut, shut or weld to make it work.