Triggers bucket

[Ewan 500 K1]

Not really any idea Ewan. It's clearly something from around the 70s, something that used the same sort of design as the 500/550s. Maybe a 400/4 or one of the 750s like say a K4/5. I can't think of anything else offhand, maybe Bryan can shed some light on it.

 ..... over to Bryan then

[Bryanj]

What size is the piston? Later 750's had a bigger piston and bigger calipers with different bracket arms and of course bigger diameter discs so looks like one of those, if you have a 750 disc about you could always fit that and make it a real mongrel, just as long as you have a good memory or accurate note book!!

[Trigger]

Ewan, Oddjob, This is why i am so confused on this 50mm arm. I was going to do a twin disc on the 550F1, and had matched the two 50mm caliper arms and the two wide body calipers up to fit the F1. Was about to start the double disc conversion when someone made me an offer on the bike. So that got sold.
So then i put the 50mm back on the black one.(where it originally came from)  And the confusion started. I have a number of arms and calipers but, all the rest are 42mm. I took it that the 50mm was from the F1, F2 , K3 and 750K. The 42mm where from CB250, 400/4, 500T. It was not until Bitsa sent me an arm that was 42mm from a 750K that i understood that the 750K had the smaller one also.

[Trigger]

OK, everything fits and lines up. Nornion was right. I have informed him off-line. Cheers for all the info. The F1 i sold must of had a bigger disc. From what Honda CB is another question. Anyone have any ideas?

[Trigger]

I have just spoke to the new owner of the CB550 F1 and he said the disc is 295mm. This explains why it fitted OK.

[Ewan 500 K1]

I have just spoke to the new owner of the CB550 F1 and he said the disc is 295mm. This explains why it fitted OK.

This thread just goes to show how uik and effective this forum is at getting to the bottom of tings ... brilliant  .. so the 50mm arm/ caliper comes from later 750's + 550F1 ?

[Trigger]

Ewan, now that is another question. Anyone out there have a CB750 F1 or F2 that could clear this up. Ewan and I may have some parts for you

[Ewan 500 K1]

Ewan, now that is another question. Anyone out there have a CB750 F1 or F2 that could clear this up. Ewan and I may have some parts for you

 

[pptom]

Very interested to know the answer to this too. The second disc setup I recently sold also has the same problem.
I removed it from a mates non running '77 550, so it either had a front end swap at some point or it was a model change.
I believe the disc is the correct 550 size, but caliper and bracket do not match with the new owners forks.

[Ewan 500 K1]

Very interested to know the answer to this too. The second disc setup I recently sold also has the same problem.
I removed it from a mates non running '77 550, so it either had a front end swap at some point or it was a model change.
I believe the disc is the correct 550 size, but caliper and bracket do not match with the new owners forks.

yep, that looks like the same 50mm bolt hole centres caliper arm ... which then seems odd that it came off a 500, unless the disc was also a larger 295mm non standard disc

Did the disc also come off the 500 ?
Does the purchaser mean that the caliper arm bracket holes dont line up with the holes on the fork case ?
What bike is he trying to fit it to ?

.. and he might not want to use the stainless bolts ... was told their low tensile strenth makes them a bit dodgy as disc bolts 

http://www.sohc.co.uk/index.php?topic=6550.msg35809#msg35809

[Trigger]

I second that about the bolts Ewan. You need High tensile bolts.

[Ewan 500 K1]

Very interested to know the answer to this too. The second disc setup I recently sold also has the same problem.
I removed it from a mates non running '77 550, so it either had a front end swap at some point or it was a model change.
I believe the disc is the correct 550 size, but caliper and bracket do not match with the new owners forks.

yep, that looks like the same 50mm bolt hole centres caliper arm ... which then seems odd that it came off a 500, unless the disc was also a larger 295mm non standard disc

Did the disc also come off the 500 ?
Does the purchaser mean that the caliper arm bracket holes dont line up with the holes on the fork case ?
What bike is he trying to fit it to ?

.. and he might not want to use the stainless bolts ... was told their low tensile strenth makes them a bit dodgy as disc bolts 

http://www.sohc.co.uk/index.php?topic=6550.msg35809#msg35809

.. and given what bryan says re pistons .. if the piston and seal are standard 500 ones , they might not fit that caliper if the caliper fits the caliper arm   

[pptom]

He might be along soon....
As for the stainless bolts - I know it can be a much discussed subject and don't want it to become the subject of this thread but my reasoning was that lots of modern bikes use 6 x m6 bolts to secure the brake discs, these are m8 and they aren't subject to anywhere near the braking forces that modern brakes produce. I think it would be one hell of a shear force to break 6 x 8mm bolts, plus there is the resistance to corrosion etc.
Good enough for an aprilia rsv4, so it's good enough for me

http://www.pro-bolt.com/stainless-steel-disc-bolt-duca-ti-aprilia-m8-x-20m-fl-head.html#.U2vqgSe9KSM

[Ewan 500 K1]

He might be along soon....

.. think I just saw him passing the window with a package under his arm 

[Trigger]

If A2 stainless, they are very soft. The modern bikes are High tensile and a lot are chromed.