Author Topic: CB750F2 .... silk purse from a sows ear.  (Read 7428 times)

Offline UK Pete

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #210 on: June 01, 2019, 08:02:07 PM »
Wow you certainly have had your work cut out with this bike, keep up the good work fella

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Offline SumpMagnet

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #211 on: June 01, 2019, 10:17:13 PM »
She's not too bad .... It wasn't expensive but was actually pretty complete, and the engine internals were sound. I could just chuck away things like this and replace...but where's the fun in that :)

I want to try and get every bit working as it should, and try and make each piece look as nice as it ever did. Just looking at the smooth and shiny frame paint makes me happy ( is that wierd??? )

I want to try and complete the rebuild without spending more money than the bike is ever going to be worth....so...perhaps the slower I work....the more it will appereciate in value...so the more I can spend...Hmmmm......
CB750F2 - in pieces
CB900F Hornet - the daily transport

Offline SumpMagnet

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #212 on: June 16, 2019, 03:53:16 PM »
Gods Holy Trousers..... I give up!

Not on the project...but on a weeks worth of effort to break down the rear master cylinder. It's not happeneing.

The adjuster nuts on the rod are welded together by rust and won;t come off...and the centre section of threads look to made of iron oxide...which isn;t helping.

Worst of all..the circlip simply will not shift. Both ends where the circlip pliers should go snapped off in the struggle, and where I can see the groove....it looks....wrong. The profile should be  |_| .... but its more ... \_/ and the circlip will not move at all. Heat didn't shift it, soaking in penetrating oils/WD40 failed, and I can't even punch the ends and make it move.

I am at the point of drilling into the groove from outside to punch an end free ..... but I don't think that's a good idea. I have run out of other ideas....so I think this part is heading for the scrap pile and the quest is on for a servicable replacement.

So...in order to make myself feel better....I dug out the solvol and started cleaning the comstars. Not that they are bad...the alloy is really unpitted ...but really more because I felt I needed to achieve something!

EDIT:
actually...drilling 2 small holes through the alloy behind the circlip, and whacking it with a drift ( well..actually a snapped off old 1.5mm drill bit ) got the clip. It came out in 2 pieces, but it came out. Now...I have to make the piston move, and it won;t right now. Unlike the front MC, you can't get at the back of the piston to drift it out. There is no 'back' you can get at. So....more WD40 has been poured in through the available holes in the back of the unit, and it will sit for a few days to marinade. ....

And I have had zero like finding a replacement unit ...so this has damn well better work!
« Last Edit: June 22, 2019, 02:17:59 PM by SumpMagnet »
CB750F2 - in pieces
CB900F Hornet - the daily transport

Offline SumpMagnet

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #213 on: July 13, 2019, 05:13:43 PM »
Well...I didn't give up..... I don't think I actually know how :)

I had decided my rear master cylinder was scrap....and that kind of gave me the leeway to get a little bit....er...brutal.

So...I drilled the head off the piston. Cored out the middle and took the head off. This was the bit that had glued itself to the bore with crud and solidified brake fluid.

Got the piston top off...and soaked in some more WD40. Then...using a pair of forceps and a needle...I teased a split into the rubber seal, clamped it and tore the sucket out of there. With that out...the rest of the piston could be pulled out.



The wreckage of the tear down looks pretty sorry for itself....

Now I will see if I can polish the bore to the point where I reckon it can actually seal on a fresh piston/seal. A little irregularity can be taken up by the seal....as long as it's not pitted or scored to ruin a seal of let fluid past. The Solvol will be broken out and I have made up some round polishing mops gluing sponge onto some old sanding tools for the Dremel...so tomorrow...I shall polish and see if I can get a smooth durface. Worth a try! If I can get it smooth and shiny...I will buy a rebuild kit and see if I get pressure.

Victory.... OK...a small one....and not by means I would recommend to anyone.... but a victory none the less!
CB750F2 - in pieces
CB900F Hornet - the daily transport

Offline Spitfire

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #214 on: July 13, 2019, 06:37:36 PM »
Nice one, hopefully it will seal, fingers crossed for you.

Cheers

Dennis

1976 CB750F

1977 CB750F2 In bits

1964 BSA A65R In bits

2000 NT650V DEAUVILLE

Offline SumpMagnet

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #215 on: September 01, 2019, 11:35:07 AM »
Pressures of life...work...and...er..life have been keenly felt of late, and it's slowed progress on the project. As has the trusty daily rider Hornet....picking up two punctures in 2 weeks and needing new rear pads. But she works for a living..so that takes priority.

But...things have been moving slowly. Flushed with success on the rear brake......the swingarm was next on the list in my efforts to get a rolling chassis. Only taken me a year to get this far.....er....yeah.

The actual swingarm p[ivot felt fine when I was tearing the thing down with no real slop or play, so the bushes will stay. The rest was not so good. Much crud had to ber cleaned off, and strangely...one side of the arm was covered with a fair bit of surface corrosion, one was good. The corrosion was chainside....so I suspect Mr Previous Owner wasn't much of a one for chain grease.

The surface prep took a while, but the paint came off easy ( I have some REAL paint stripper... ) the chain guard threads were cleaned up, and a sheared off grease nipple was found on the swingarm. Nice to see Honda put one there....but this one was a goner. Also beyond usable were the rubber bushes for the lower shock mounts.

these had me stumped until I found a brilliant solution...well..I say 'found' ... my brilliant solution was to ask on here....and I got a souiltion that worked well!

I attacked the fossilised rubber with an old and blunt 3mm drill bit, drilling holes through the crumbly rubber around the edge between the inner and outer metal sleeves. This allowed me to pull out the bits in between with what are actually locking forceps I picked up years ago at an auto jumble. Then...I popped a hacksaw blade in and cut through the outer sleeve almost through...then punched in the edge to collapse it. On one I scored slightly through the sleeve....but no harm was done and teh metal on the swingarm was barely marked and not 'grooved'.

Now I can order replacements and press them in when the paint has had a few weeks to harden.



Happy days.

Oh...yeah...one fly in the ointment though...well actually...fly in the damn paint! Sprayed it on the washing line as it was a nice day. Then carried it into teh shed to keep it away from flies, dust or the chance of rain. Hung up in shed and I see a damn midge buzz past and settle on the fresh, tacky paint. Well...I know better than to try and sort that now....so midge is doomed, and I will have to flat that back later. It's on the underside....so no big deal. Just bugs me .......
CB750F2 - in pieces
CB900F Hornet - the daily transport

Offline Spitfire

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #216 on: September 01, 2019, 01:33:21 PM »
Nice to see a plan come together

Cheers

Dennis
1976 CB750F

1977 CB750F2 In bits

1964 BSA A65R In bits

2000 NT650V DEAUVILLE

Offline SumpMagnet

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #217 on: September 08, 2019, 01:08:05 PM »
No stopping me know...er...well...until I had to stop anyway.

Swingarm painted...



and then did the battery box and torque arm.

Battery box was in a rusty state at the bottom, and needed much sanding and prep to be paintable. Battery acid leaks and general neglect means corrosion is common. Tehy are also very fiddly to sand, with bits everywhere.

Need to order my shock bushings and I can put together the swingarm with the worn out old FVQ shocks going in for temporary. They will be replaced with modern/new units.
CB750F2 - in pieces
CB900F Hornet - the daily transport

Offline Crispy

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #218 on: September 09, 2019, 09:16:42 AM »
Just sat and read your story from start to finish, great read you should write a book! I can identify with a lot of your experiences, the highs and lows, master cylinders  >:(  and getting a lot of pleasure from simple things like transforming some part with a bit of paint or succeeding in doing something that you've never done before. Good luck with the rest of the rebuild and I'm looking forward to reading the next chapter!  ;)

Offline SumpMagnet

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #219 on: September 09, 2019, 05:55:42 PM »
Appreciate the comments :)

This is part resto...part therapy for me. Documenting the steps and the experiences is fun, and when it's all done, I can put it all together with the receipts and the pictures, and if I ever sell this thing...it will come with a story!
CB750F2 - in pieces
CB900F Hornet - the daily transport