Topic: Options for non-standard parts

[eigenvector]

I must have been high when I bought that CB700SC, nothing on that rig is standard. 

I am looking for replacements to the exhaust studs and come to find out they're also one of a kind.  8mm to 6mm 55mm long.  When I took off the Yoshi exhaust I saw that it wasn't made for this bike - the exhaust flanges were all F'd up and it was clear the owner used the 'bigger hammer' method of installing it.

Have sized up as many options as I can find, but nothing is looking good - all of them have some problems.
I can machine them from 8mm rod blanks, I can attempt to recut the threads on a 5/16 to 1/4 reducing stud (5/16 and 1/4 are both ~8mm and 6mm), I can try a thread insert to reduce the exhaust hole to 6mm (like it should have been all along!!  Honda you bastards), or I can try using a thread reducer/inverted flare nut.  I can also e-bay them but I'm not sure I want to persue this route except as a last resort.

If I machine them, probably the best solution, I'll have to farm that out.  I don't have a lathe, but I'd also have to buy like 50 of them to make it worth their while.


What does your experience tell you in situations like this - when you have a part which is no longer available and not easily produced from existing options?
So far my experience is telling me to hit up a machine shop and have them made.  But if I can find a flare nut that will work that doesn't sound like a bad solution either - if I can find one in steel rather than brass.

[demon78]

What about Helicoils ?
Bill the demon.

[eigenvector]

That's an option, but for some reason I thought helicoils would ruin or alter the existing 8mm hole.  I am really interested in preserving the original hole in case I do eventually have the bolts machined.  I operate on the principle that I can't put the metal back once I drill it away - so first try to save it.

If helicoils will preserve the original 8mm hole, then problem solved - end of discussion.  I can go with a timesert as well - I do already have a 6mm timesert kit that I used to repair the valve cover mounts on my CB750.

[demon78]

Well it's been a day or two since I last used them but It's a permanent solution and they are in metric I'd check with them and see what they say.
Bill the demon.

[eigenvector]

Honda used a 8mm to 6mm reducing stud, 55mm long (edit, corrected to 55mm).  So I have an 8mm stud hole in the cylinder head and a 6mm hole in the exhaust header.

[madmtnmotors]

What's the header flange look like? Can it be drilled to accept an 8mm stud?

[eigenvector]

I would rather keep it stock - but yes, potentially I could oversize the flange holes.  My guess is that all I'd end up doing is cracking the flanges but if no other solution presents itself then that could be the best solution.