BS34 Carb Diagram/Schematic/Exploded View

there is a minuscule spring/ball that popped out of somewhere but not sure where; is this a detent for the choke pull rod? If so, I assume I can deduce which carb body it goes into as I expect that I'll finding a corresponding divot in the choke pull rod.
Correct. Iirc it's the left carb, but the choke shaft will let you know. They're a bitch to install. Grease keeps 'em grounded. ;)
 
The parts diagram calls for 2 sets, one in each carb. Sometimes you find two, sometimes only one.

That small o-ring is most likely for the float bowl drain screw.
 
Correct. Iirc it's the left carb, but the choke shaft will let you know. They're a bitch to install. Grease keeps 'em grounded. ;)
Thanks Jim. I missed the earlier part of the thread where this was made evident. Shame on me!
What about the little O-ring; looks like it goes under the screen on the needle valve body. True?
 
The parts diagram calls for 2 sets, one in each carb. Sometimes you find two, sometimes only one.

That small o-ring is most likely for the float bowl drain screw.
Sorry 5T, didn't see your response as I was typing my last reply. Not sure that the O-ring goes on the drain screw, as the drain screw has a tapered seat which shouldn't really need an O-ring. I'm thinking it goes between the needle valve screen and the needle valve body. Possible?
 
No, it goes on the drain screw, just under the head .....

BowlDrainScrews.jpg


The float needle seat o-ring is larger and thinner .....

Float Seat Assembly.jpg
 
Last edited:
Huge THUMBS UP, Skull. Thanks most of all for the BS repair/overhaul document. I also found 5T's carb guide and between the two, I think that I have all the bases covered. What remains to be seen is how much of the buggered stuff comes in the overhaul kit from Cruzinimage. The stuff that appears to be missing is the pilot jet plug, the pilot screw, its spring , washer and O-ring, the main jet washer...we'll see when I receive those kits.

How did you find the Carb kit. Are the needles much different to factory??
 
How did you find the Carb kit. Are the needles much different to factory??
I used only those parts of the Cruzinimage kit that I really needed to replace damaged/deteriorated parts. The original Mikuni needles were fine, so I did not change them. I also did not compare them to the kit's needles. I may have another set of needles, so I'll have a look to see if I can answer the question.
 
The Cruzinimage kit contains two generic needles, a Y265 and a Y267. The Y267 appears to be a copy of the '78-'79 5O2 while the Y265 looks to be a longer version of the XS400 5Z1 .....

KitNeedles.jpg


I have the XS400 5Z1 needles in a couple sets of '78-'79 BS38s and quite like them. I've put the Y265 copy in a spare set of BS34s I refurbed but have yet to run and test them. They are fatter than the original 5HX12 which would make them leaner, so I'm not sure how well they're going to work. I'm hoping I can jet up to compensate. It took some fiddling on the BS38s to get them right and that including bumping the mains up another size (from 140 to 142.5).

KitNeedleTips.jpg
 
Carb Schematic. I like pictures. If you want to have a 1/2 choke then a recess can be drilled on the rod between the full choke and no choke
Sorry to resurrect an old thread, but can anyone tell me what the “other” main jet (#44 in the diagram) is for? Does it ever get replaced with a different size jet when someone tunes their carburetor?
 
44 is the pilot air jet. You can change it, along with the pilot jet and turning the mixture screw to fine tune idle and low speed mixture.
For instance... one pilot is too lean so you go up one size. Now it's too rich. You can swap the air jet to find the sweet spot between the 2 pilot jet sizes.
 
Back
Top