Honda-SOHC

Well that clinches it !  My hub dimensions are exactly same as yours so it looks like the swingarm's the problem  -  mine being 5mm narrower than yours.  Having said that, if I've got the wrong swingarm it might not just be the overall width that's wrong but the offset too.  So I'm on the lookput for a swingarm with 240mm across the inside faces.  Anyone out there got one for sale ?

I've had a gut feel that this is the trouble spot all along and made a bid for the one captaindonut sold on Ebay last weekend but missed out 'cause I wasn't at my PC when it closed.

Pity about mine, with 235mm across the fork ends  -  it's all powder coated and shiny so will be looking for a good home.

So grateful to all who've contributed to the debate and especial thanks to Steve for his input.

Hope I can pass on some of the stuff I've learned in the same way.         Brilliant !!

Thanks Timbo !      Good of you to respond like that.  So your swingarm is 5mm wider than mine.  Well, that extra 5mil would help, but I'd still be looking for another 5 at least, so I'm not out of the woods yet.  The 'chopped' spindle spacer I have (and which I now realise has been used on this bike by some PO) is 24mm.  I went out and bought a new 32mm one  -  hope it will still be needed when all this shakes down.

Hi All
I'm Dave from Stockport.  'Oldbuthopeful' refers to the fact that I'm old enough to have ridden a 650 Ariel twin at 90mph on an 'A' road with cap turned back-to-front and not broken the law.  I was 17 at the time !   The 'hopeful' bit is about getting the CB550K3 I'm building onto the road this summer.  Well..........we all have to have a dream !
My wife thinks I'm slightly bonkers, building a bike at my age but, not having had a bike for many years, I decided last December to buy a job lot on Ebay and have a final fling. It was done on a bit of an impulse  -  I've never had a 'four' or even ridden one but it's a bit like climbing mountains,  you don't have to have a reason to do these things, you just do them because they're there and anyway, time's running out !
So this box of bits is coming together quite nicely  -  wheels rebuilt, forks re-chromed, many weeks pocket money spent with Dave Silvers and all being assembled onto a frame that one of the PO's had had powder coated. He'd obviously started the rebuild -  yokes, swingarm, airbox, fuses, loom etc all fitted but I've come to a dead stop because I can't get the back wheel complete with spindle, chain adjusters, collars etc to go into the open swingarm fork ends.  I need another 10mm or so in width and am beginning to think the cut-down bobbin spacer in with all the other bits must have been some PO's answer to the problem.  Trouble is, if I use that instead of the new bobbin I  bought, the wheel appears to be slightly offset to the right.  Any help from you guys out there would be greatly appreciated.
Good job I can keep stroking the re-sprayed tank and the new seat !!