Topic: 1982 Honda CB 750 Restoration Project - Gas Overflow

[oxygen147]

Hi All,

I am in the middle of a project with a 1982 honda cb 750: .  Just rebuilt the cards, replaced the petcock and finally got it running however... when it is running gas pours out of the carb overflow tubes for all 4 carbs.  Any ideas on why this is happening and how i could resolve?

Here are some pics and a summary: http://www.danielpeterjackson.com/1982-honda-cb-restoration-project-update/

Thanks in advance for any help,

Dan

[MrZxp]

Nobody seems to have noticed your post Dan, so I figured I'd have a go at helping you out! 

There could be crud in your carbs causing the float valves to not properly close or your floats themselves could be set at the wrong height, introducing an excess of fuel to the bowls. Also the float valves themselves could be worn (probably not likely considering the low mileage) but a possibility also. This was the problem with my 550.

When you had your carbs off did you give your tank a thorough cleaning? It might be introducing foreign matter.... an inline fuel filter will help here...

Cheers, Phil

[Hush]

If you took the carbs apart did you fit all 4 sets of floats in upside down?
I did 
It takes pure genius to do that but I can laugh about it now.
The fact that all 4 carbs leak is unusual.
Either you fitted something wrong (genius level)  or there is something worn on all 4 carbs (unlikely).

[oxygen147]

Hi Guys,

Appreciate the response and I agree that it is likely a mistake I made when putting the carbs back together.  However, I did not remove the floats, is there any other areas that could cause this leaking or is it most likely the floats?

[planning on pulling out the carbs again and checking the floats next week, want to make sure if there is anything else to check, i look into it while the carbs are off]

Thanks!

If you took the carbs apart did you fit all 4 sets of floats in upside down?
I did 
It takes pure genius to do that but I can laugh about it now.
The fact that all 4 carbs leak is unusual.
Either you fitted something wrong (genius level)  or there is something worn on all 4 carbs (unlikely).

[MrZxp]

Hmmm - sometimes the brass overflow post in the bowl can have a hairline crack... although it would be unfortunate (and extremely unlikely!) for all four to have the same malady... 

Other than that, apart from what has already been mentioned, I really cannot think what else could be causing the problem.

These would be CV carbs too I would guess? Not overly familiar with their operation either, could well be something I know nothing about!

Perhaps you could try posting a question in the Other Bikes category - it gets a bit more traffic there, others would maybe able to help?

Cheers, Phil

[Hush]

That's a phatt looking 750, must be the custom model I'm guessing cos I haven't seen a 750 like that here in NZ.
What did it set you back $$ initially if you don't mind me asking?
I think the clue to your problem is in your own statement "I did not remove the floats"!
If you did not take the floats off then you also did not drop the float valves out.
These little suckers become very used to either being jammed hard into the bottom of the carb or hanging loose when the floats dropped, this occurs when these bikes are left for long periods under trees and in barns etc.
You seem to be spending so mauch anyway on this bike and it sure looks pretty, the minor cost of replacing the carb float valves would be almost compulsory for you as you will have to do it sooner or later.