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80 Super Sport Accelerator Pump Nozzle

Exit39

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Hey everyone. I have a 1980 CB750F Super Sport project. While rebuilding the carbs I noticed in carb #1 (left side) the accelerator pump nozzle was damaged by the previous owner. No gas nor cleaner will get through and it looks like somebody tried to remove it at one time, only to damage it. Question is, because it's pressed in with no access from the bottom like the other carbs, can this be replaced? If so, how so? Or do I have to find another #1 carb? If so, does anyone know where from or who might be selling one?

Here's a pic of the damaged unit. Any assistance is most appreciated!

20200703_150151.jpg
 
You could drop the accelerator pump system entirely like the Euro models do. They don't have them at all.

Nobody I know of ever made replacement parts for that.
 
You could drop the accelerator pump system entirely like the Euro models do. They don't have them at all. ....

Ok, I can eliminate the pump system altogether, which will solve my issue with the damaged nozzle. Also, I can eliminate the Air Cutoff system as well?

Any information on deleting the accelerator pump system would be great. Info on BOTH system deletes as well, if you know. :)

And thank you for your involvement in this.
 
Okay, so I seem to have found a #1 carb, but the numbers don't match according to this chart:

http://www.hondachopper.com/garage/carb_specs/carb_specs.html

The carb I have is a VB42B (CRH) for a 80 CB750F.

The carb I found is a VB42A (FTA) which according to that chart may be from a 78 CB750F.

The differences listed appear to be limited to the type of float and jets. So my question is, are those simply interchangeable with my components, or are their also physical differences internal to the carb body itself? Exterior, they are identical.

Also, I found another carb and it is a VB42B but from an '82 CB750, they say. I think it's from an '82. But by all respects to the chart, it looks like it should be a match, body-wise. Help confirm?
 
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There is no VB series carb for SOHC 750 which is what a '78 is. ALL VBs are CV type carbs and use began in '79 on DOHC. The carb from '82 if correct will not have pressed in pilot, it screws in. It will work though.
 
Thanks all. I placed the order for the 82 and hopefully will be able to make her work. If not, I'll be pursuing any DIY option I can come up with. 8)

Here's some pics of the damaged one that I didn't have at the time of posting. Really chewed and mashed over the port; no fluid gets through.

20200704-185005-HDR.jpg


20200704-185154-HDR.jpg


20200704-184903.jpg
 
Oh, there's likely a way to recover that carb but the problem is how you commit to do it. I would remove the brass bb underneath that allowed the vertical passage to be drilled and then drill upwards until into the nozzle then you have to drill from the carb entrance to go through the top to the other side and then plug the outward wrong facing hole side as well as the bb hole. Typical carb mod work but not for those who never have done it. You would be basically redrilling the original shooter passage out again. You have to find the hole size of the other 3 first to get some idea of it. The hole actually aims to hit the nozzle the needle goes into but shoot the others and see where they hit. Pump shot is intended to hit something to further break it up to dissolve faster in the carb throat air.

Or maybe clamp locking small visegrip on the nozzle top and while not crushing it enough to break it off. Then pry up on the visegrip with a slot screwdriver against the carb material to possibly pull the nozzle out the top of hole. Then cobble up another nozzle of some type.

Haven't done it on these yet but have done that work on other carbs before.
 
If that brass nozzle OD lucks out to be close to a standard size of brass tubing then a piece of K&S brass tubing could likely be used to make a nozzle, the brass is found in bigger hobby shops.
 
New issue fellas regarding the accelerator pump itself.

After thoroughly cleaning the ports and valves on the pump bowl and fuel bowl and ensuring flow using pressurized carb cleaner everything works, disassembled. The diaphragm looks good when viewing it back lit, and is flexible with no tears. With the fuel bowl off the carb, I filled the bowl with gas and tested the pump by pressing down on the rod. The fuel gets sucked into the accelerator bowl, but does not spit out of the valve, instead the fuel fountains back up in the bowl. I tested both valves and they flow nice even sprays through all 4 sides using the carb cleaner. This leads me back to the diaphragm because even though it looks good, maybe it's mashed a bit (internally when sealed) and not creating enough pressure? No fuel leaks out the assembly itself.

Just don't want to waste money on a new diaphragm if something else is at play here. Can't think what though.

What say Ye?
 
If it was pump diaphragm the fuel would not pull into the pump.

One way check valve issue in the bowl. Pump intakes fuel through it open and then at pumping out the one way check seats to block backflow back into the bowl. It's not blocking.

'.....they flow nice even sprays through all 4 sides using the carb cleaner.'

That's on the pump intake phase, they must cut off and seal 100% on the pump exhaust phase. What makes it a one way check.
 
If it was pump diaphragm the fuel would not pull into the pump.

One way check valve issue in the bowl. Pump intakes fuel through it open and then at pumping out the one way check seats to block backflow back into the bowl. It's not blocking.

'.....they flow nice even sprays through all 4 sides using the carb cleaner.'

That's on the pump intake phase, they must cut off and seal 100% on the pump exhaust phase. What makes it a one way check.

Nice! Excellent answer. I have seen where the plastic valve/spring/ball have been removed and along with the inside of the cavity cleaned. I suppose it's doable with the brass one. Sucks because I already ordered a new diaphragm. I'm going to continue the quest of backfeed cleaning the valve with a small wire. You're most likely spot on, and might be something wedged in there preventing the spring/ball from closing the valve.
 
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