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CB750F2 .... silk purse from a sows ear.
SumpMagnet:
Only been able to do a few small things, but some major decisions await that could affect teh whole direction the project takes......so I got some serious deciding to do...
Today, though, I decided to try and sort out my poor old exhaust headers. They are not in bad shape...but where the join to the silencer sits....corrosion had set in. The back end of the pipe was a wreck. BIG hole blown out and the thing was rotten as an old pear. But the headers were nopt so bad. When I took off the clamp and chiselled off the crusty gasket...I found a chunk of the surface under the gasket was ......not metal anymore.
It was quite localised, with an area the size of a postage stamp gone.... so I figured I would have a go at fixing it.
I cut out the bit that looked bad....only to find I needed to cut out about 4 times that to find metal that wasn't too thin. It's bad enough trying not to blow holes in sheet metal without it being so thin you can poke holes in it with your finger....
Found a bit of scrap steel the right thickness....and spent a while shaping it. Got it perfect roundness...then realised it's only round at the end...and had to 'unround' it to fit right.
Fired up the old MIG welder....and then spent a while grinding it back and making it nice. Found the pinholes I had missed....filled them...ground back again... Quite pleased with the end result. Well..on the outside. It's not so nice on the inside, but there isn't a whole lot I can do about that. Its solid though, which was the thing I needed.
My problem now, though, is how to proceed. It was always my intention to go mildly cafe-racer on this, but the question now is how far to go down that route. The only rule here is I will not cut,slice or ruin anything Mr Honda made....but the seat is in the bin ( it was too far gone to save and not a genuine part anyway ). The exhaust is toast at the back. I also have some issues with the brakes.
The rear brake has issues with the master cylinder and reservoir...and the actuating rod. It also has a shot piston and needs new seals, dust caps and hose. I have cleaned a LOT of corrosion out of the master cylinder...and don;t know if it will actually hold pressure. Trying to find a decent replacement has not turned up anything that looks any better than mine...and some that look much worse. The fronts need hoses and new pistons....but at least the rest is OK. Need to read up on the seals...as they don;t look directional...but I want to be sure before I put them in!
I had a glimmer of hope when I was told that the brakes off a later CB750F/900F could be used with the brackets and give me twin piston calipers....yeah. They are rarer than the hens teeth I am already looking for. So that was a no
plan a) rebuild rear master cylinder and hope!
plan b) use a non standard replacement master cylinder. This will involve making a new bracket, which is no big issue, but I have no idea how to select a suitable replacement. Ideally I would want one that shared the same hose connections...so I can buy a proper hose...and be able to fit it.
Plan b) is where things get complex though.....as if I am making brackets....I could get some ally and make footrest brackets to fit rearsets....which leads into exhausts.....
I simply cannot find a set of exhausts I like. The Delkevic straight pipe system looks OK...but I do not like the lines under the engine not being horizontal. I could get my headers rechromed....if I can ever get the damn things apart ( one header out....one not shifting!) and fit a replacement silencer....but it's not convincing me. The only setup I went YES! at was a custom setrup on a KZ....which would mean having it made. But..if I am making custom footrest hangers.....
Just got no idea how to find a compatable master cylinder.
Oh well....time to drink beer and ponder. Usually works
McCabe-Thiele (Ted):
Thinking of your exhuast system particularly the manifold pipes - how about having them all made in stainless steel?
About 20 years ago the front pipe on our Merc a W124 260E was very badly corroded due to the PO visiting building sites so cement slurry rotted a lot of underbody parts.
A new MB front pipe was daft money - over £500.
A firm in Huthwait, Notts http://www.stainless-exhaust.com/ basically made a replica manifold a 6 into 1 system. I've just looked it up my manifold cost me £200 in 1999 - including fittting.
There is a similar firm called PD Gough who build similar systems they are in Watnall & have a website https://www.google.com/search?q=pd+gough&rlz=1C1CHBF_en-GBGB934GB935&sxsrf=AOaemvKCWX7C9DfnQgrAv3U9CK71BbeZLQ:1630619189766&tbm=isch&source=iu&ictx=1&fir=hyf40v1P6rRpDM%252C8yiKlWGz0XjIdM%252C_&vet=1&usg=K_Nbz7H1lSAlaJEX6q0gauX7u1-Ao%3D&sa=X&sqi=2&ved=2ahUKEwiBjsfsoeHyAhVpQfEDHThdBm4QuqIBegQIbBAD&biw=1920&bih=937#imgrc=hyf40v1P6rRpDM
Maybe there is someone similar near you offering a similar service - might be expensive - we had a full system made & fitted for our SL back in 2003/4 by PD Gough's they even asked me how loud I wanted it to be - they baffled it accordingly so you can't tell it from a standard system it was way cheaper than a genuine MB system.
SumpMagnet:
Thats an interesting thought. If I can find a reasonably local supplier.
There are plenty of places selling exhaust pipe and pre-bent mandrel bends. Now....my little home MIG kit isn't up to a neat job ( not my welding skills at fault...surely...I mean....blobs and spatters add character..) but I could tack weld bits together and get them professionally welded up. Most custom pipe makers seem to need the vehicle to build the system on, which is a bit of an issue for me.
To ride the bike..I need an exhaust...which means I either paying for a trailer job, or finding another way. It's either that or finding someone who has the right patterns for making up a suitable system. I've contacted a couple of possibles, and will see how I get on.
Could be interesting!
K2-K6:
I've made accurate forms in tube before for rally car roll cage on which the tubalist (made up name for man wot bends pipes) got me to bend sections in aluminium welding wire to work from as they involve compound bend section. He was very competent in that craft though, but it is relatively easy to interpret if given an accurate form.
You can also do things like thread foam pipe forms (like those swimming float things) onto the wire to get clearance etc.
Spattering on fluxed welding wire, keep anything with flux component in airing cupboard or similar ensuring it's bone dry as it's the moisture content that makes it spatter and stick. It's much more consistent when dry and you'll usually be able to use a more accurate amperage to weld with if you're not coping with it being awkward.
K2-K6:
Also may be of interest
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Loose copy of Yoshimura pipe made by "Carpy" expat brit bike builder in USA, he has ordinarily been helpful of shipping protocols from what I've read and so may be an option you'd like.
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