1972 750 SF carb options

eyeguy

eyeguy

Junior member
Location
London- where the streets are paved with gold
Chaps
My unrestored SF is a thing of great joy, but the restored bike appears to be , umm, challenged in the carb department. The vhb 30's were worn throughout and I changed all the jets, fitted the nearest needles ( the v3 is no longer available, so they suggested k31) but it's all so wrn that it runs hopelessly rich. I even tried smaller pilots ( 45 from 55) which helped a bit, but it's quite rough still. To compound matters, having spent ?120 on bits, the LHS float bowl thread is partially stripped in the carb body- grrr.
As my bikes are riders, I'm of the inion that lobbing this worn out junk and fitting new carbs might be the way to go. Anyone here have experience of alternative figments. I thought perhAps phbh 30's as a sort of period looking replacement.
Any thoughts and jetting advice. Uh appreciated.
Cheers
ATG
Pauly two lavs
 
  We fitted a pair of phf 32's off a triple - you can use your pilot adjusters off your VHB's and use conventional tops - probably quite a few of them about - the triple stubs can be fitted with some mods too - Regards - Phil
 
I have a similar issue with some PHF36 Dellortos - can't get them weak enough.
I'm a bit confused though. If you've replaced the needle and jets then the only worn bit left is the slide and where it runs.
Wear there is going to let more air and cause weakness isn't it?

My engine broke going back from Baskerville Hall but when I've got that fixed I'm going to see if I can ensure the choke circuit is properly blocked off.

 
Hi olly
I think you're correct- in theory. The reality, as I've often found, is that the rattlly, loose slide causes too much oscillation in the needle itself making correct fuelling setup impossible. It's fair to say that I'm a bit anal when it comes to carb setup and when I test bikes for the mag the proud owner tells me how it runs perfectly as they  extol the virtues of the repainted tank and shiny chrome, whilst I'm thinking how that money could have been better spent on swing arm bearings and a carb rebuild!

I'll talk to dellys tomorrow and see what they suggest, and will report back!
Cheers

Atg
P2L
 
Yup, I changed every brass part and fitted a complete seal/gasket kit. Hence the price :'(

There are no NOS slides left, that and the lack of V3 needles seems to be the main problem, sorry to say. In fairness the bike is 41 years old and has been sucking unfiltered air all its life, it doesn't owe me any good reason to carry on forever, but I seem to be the owner that's finally decided to sort it out properly, ho hum....

Cheers

ATG
P2L
 
Paul,

It's not really the slide that causes the wear at the needle and its' jet, it's the loose fit of the needle in the slide, very common fault in almost all types of slide carbs.

I can check if I can source further V3 needles, I've supplied several in the past.

New slides are not available, but I find that they are of secondary importance.  When fitted with new brass-ware, VHBs work surprisingly well again. 

piet
 
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