Topic: Vintage Keihin CR31 Carbs

[H2Eric]

I've had a set of these on my CR750, but the spacing on this particular set of the carbs is not quite right for the CB750 cylinder head as they were spaced for the Suzuki GS1000 and/or Kawasaki Z1 and as a result require a set of special inlet rubbers. Unfortunately these rubbers have all split badly. They originally came from Mark McGrew (M3 Racing). Does anyone know of a source for these? Failing that it looks as if its possible to respace the carbs (the gap between 2 and 3 is too big), has anyone tried this? If so, how easy was it?
All help and advice gratefully received.
Eric

[PeWe]

Look like the rubbers Mikuni VM29 Smoothbore used.
SUDCO sell them.

[Jerry Rxman Griffin aka MuthaF'er]

The NEW CR31's use K7/K8 manifold rubbers for a standard head ie +1mm on the carb side. If used with a F2/F3 head then you would need the rubbers for this head ie +1mm on BOTH ends. I do not know how the ticklers measure. The F manifolds are difficult to source as original equipment. I picked up my set from Kenny at CycleX. He matches his sets by length meaning the ones I got from another vendor/vendors have different lengths in the set.

[H2Eric]

Thanks for the info guys. I'll try Allens Performance here in the UK to see what they can supply.

[H2Eric]

I'm still searching. Drew a blank at Allens Performance and the Sudco ones apparently only fit the Mikuni VM29 smoothbores and have an I.D. of 34mm.
The early (tickler) CR31 carbs have a 40mm diameter spigot.
The inlet rubbers for the CB750F2 may fit if the carbs are spaced correctly, which can be done, but without knowing the dimensions of the F2 rubbers I'm very reluctant to take a punt as they don't come cheap.
I'm waiting for a response from CycleX, but if anyone has any further suggestions / info I'd be most grateful.

The alternative is to fit a set of modern CR31 carbs, but the bike wouldn't be a replica of Mr. Honda's original 1970 Daytona winning bike, which it what I've tried to achieve.