1981 CB400T hawk carb issue.

M

mustang319

New Member
I own a 1981 CB400T hawk.

I am having one heck of a time with the carbs. After rebuilding my original carbs that sat for 10 years and thinking they were toast I bought a set off ebay. Rebuilt them with the new parts from my original carbs. All new parts.
I thought I had a needle seat issue on the originals but now I'm not so sure. The fuel would drip out of the overflow tube. After rebuilding the ebay set I still have the fuel overflow problem which leads me to believe something was missing in the rebuild kit or I'm missing something. I found a small ball bearing about the size of a BB like in a BB gun from the ebay set in the accelerator pump cover. The parts fiche doesn't show it. I'm thinking that my overflow problem isn't a seat issue but a shut off problem. I'm also thinking I may have had one in the original set and could have lost it when I soaked them out but not sure. They were pretty gummed up.

Has anyone rebuilt a set that could give me a little help via email or phone?

How about a better drawing than in the Honda manual?

I'm missing something so simple and the drawings on line just didn't show this BB. It definitely came out of the accelerator pump section.

Its the only problem I have run into.

The original rebuilts ran but would drip. I havnt put this set on the bike due to the dripping.

Someone else had to of have this same problem.


Thanks in advance
Mike
 
I apologize if this seems too obvious, but are your floats set properly? That would sure cause some dripping.
 
I was thinking that. I shimmed them and the same side was still dripping. The needle slides into the plastic holder on the plastic float. I see no way of correctly shimming them up. What I did was jam some foil under the springy part of the needle. I also took the needle and float from the side that was not leaking. No change. I was not able to make the other side leak.
 
Are you sure you have the float bowl drain screw screwed all the way in? If not, fuel will leak from the overflow tubes. Check to make sure the drain screw is not damaged as well preventing it from seating correctly. Also, have you checked the overflow tube (thin brass tube) in the bowl itself to see if its cracked or anything. Could be damaged and causing fuel to drain down the overflows. Swap the float bowls to see if the problem follows it.

A buddy of mine bought aftermarket carb kits for his CX500 (which has the same or similar carbs) and he found the float needle to be shorter than the stock one and this was causing him issues like you're having. Not sure if this could be the issue with yours but something to consider.

Do the carbs drip when running or only when the bike is off?

I had my 400T carbs completely disassembled and I don't recall a ball bearing, however my memory is not the best. :)
 
If its leaking across both carbs, bottom line is that its getting too much fuel into the bowl. Did you use the floats that came with the new carbs, or your old floats? Are the seats replaceable?

Since its happening on 2 different banks of carbs, but on the same carb within the bank, im guessing its something you brought over from the old carb, or you just got really, really, really unlucky. Maybe try swapping the float and needle (and seat if it comes out) from one of the "Good" carbs from the old bank if possible?
 
Both of you folks have given me a idea. I will swap the float bowl and everything except the Accelerator pump.

Will be back later tonight with results.

THANKS!!!

Mike
 
Heres what I tried. I took the float bowl and filled it with water and let it sit. No leaks. Tried the old parts that I still have and still have same problem. Took the slide section apart and put old parts back in. Still have a drip from the overflow. If I take and push the float up by hand the needle shuts off completly. No fuel at all. I wonder if I could have 2 bad seats on the same side. Am going to try and pop it out tomarrow.

Will tell more later.

Thanks for the sugestions


Mike

Added this after thinking. When you said shim the needle were you talking about the fuel needle or the slide needle?
 
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