CB750C Carb 2 leaking fuel, entire bike runs only on choke

deeveeance

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Hello all, picked up a project for only the cost of the uHaul and gas by trading an unused laptop.

1982 CB750C

Previous owner had new baby, had the bike he wanted to work on, no time, sky is blue. He mentioned a gas leak, and he thought it was the bowl gaskets. Had the part, no time.

Swapped the laptop, took the bike home.

As the title says, after taking it apart and replacing just the gaskets (in hindsight, that was stupid and I should have just checked everything else on the carbs), carb 2 is leaking excessive amounts of fuel via the ejection ports, routed to the bottom via thin tubing. Bike only runs on choke, then dies down.

I was doing a bit of searching, found a couple videos, and a thread on here with the advice that the "idle circuit in the carbs are plugged" on someone else's bike with the same issue.

Anything else I should check for? I have the Clymer's book coming in the mail next week, but thought I'd ask here to see if anyone else ran into this issue.

Thanks in advance, sorry for the novel!
 

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DetailGuy

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Having sat, depends on if the gas was left in or carbs dried out...

A full carb clean is the only way, check the seating of all the rubber sections..

Check out
#motorcyclemd Cody is a master Honda Bike mechanic, he has plenty of video on similar things.

I took my other bike to a shop, for another repair it too leaked all over the shop. He too cleaned all the carbs put them back on,leaked again..mmm took them off to find another problem,so yet it does happen always fixable..could be old bad gas that has clogged the system.

#mustie1 is a big bike, carb guy on utube, good luck. 🇬🇧
 

scoleshi

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Hello all, picked up a project for only the cost of the uHaul and gas by trading an unused laptop.

1982 CB750C

Previous owner had new baby, had the bike he wanted to work on, no time, sky is blue. He mentioned a gas leak, and he thought it was the bowl gaskets. Had the part, no time.

Swapped the laptop, took the bike home.

As the title says, after taking it apart and replacing just the gaskets (in hindsight, that was stupid and I should have just checked everything else on the carbs), carb 2 is leaking excessive amounts of fuel via the ejection ports, routed to the bottom via thin tubing. Bike only runs on choke, then dies down.

I was doing a bit of searching, found a couple videos, and a thread on here with the advice that the "idle circuit in the carbs are plugged" on someone else's bike with the same issue.

Anything else I should check for? I have the Clymer's book coming in the mail next week, but thought I'd ask here to see if anyone else ran into this issue.

Thanks in advance, sorry for the novel!
When filling the float bowls after disassembly, make sure the bike is on the main stand not the side stand. Yes I did have this issue a few times in a row. After putting on the main stand, the issue stopped happening. I figure the float somehow gets hung somewhere during filling and will not float if it is on an angle after being empty, or the overflow starts before the float can close the float needle valve. Fuel will just keep coming out of the overflow if on enough of an angle.
 

Tomos

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You may have several problems with that carb.
- draining screw tip is damaged,
-draining screw gasket blocks screw (to tick or damaged)
-bowl seat mating surface with screw tip is damaged,
-over flow bowl tube(brass tube)is cracked or loose in bowl.
I hope this helps.
Regards Zoran
 

DetailGuy

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You can do a leak test, make a frame over a plastic box, fill with some fuel to see if it is leaking prior to fitting to the bike.

Any good new have you managed to repair them ?
 

ricerocket71

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i wold recommend looking at each carb (one at a time).
take of the float cover and turn gas on. you can then use your finger to lift float. (if gas stops that one is good).
continue to do this to all four. (most times it's only one float dirty or stuck )

Good Luck
 
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