Topic: The infamous dripping carb secret REVEALED!

[Aaron J Williams]

I rebuilt the carbs on a customer's bike so he could go on a 1300 mile trip around lake Superior and when he got back he told me that 1&4 carbs were dripping fuel. Since I had replaced sunk floats on 1&4 I suspected that the used floats I put in were sunk also or the float level was a little too high. I checked the floats and level but both were spot-on. I lowered the levels to see if I could stop the problem but the dripping continued. This morning I decided to put 2 different used floats in and see what would happen but when I removed the float bowls they were almost empty. A closer inspection revealed this:



There were vertical cracks up the side of both float bowl overflow tubes! I took some bowls off of parts carbs and one of them was cracked too. After replacing the bowls with good ones the bike no longer drips. So if you can't stop your bike from dripping no matter what you do, look for cracked tubes.

[hcritz]

Hey Aaron...
I've seen this before as well. I think it's probably caused by moisture/water getting in there and freezing...splits the tubing.
Can be REALLY hard to see!

[Aaron J Williams]

Yeah, I totally missed it when I rebuilt the carbs. At least now I know to look for it in the future. It looks like water split them . I'm going to try soldering the cracks shut and see what happens.

[hcritz]

That will work fine...
Most of them you can pull out if you are careful...easier to solder that way.

[Magpie]

I used JB Weld on a cracked fuel tap pipe and it seemed to work fine. Just mixed it and smeared it all over the pipe to prevent more cracks. Should be fine for carb overflow pipes.
Cliff.

[SteveD CB500F]

Nice one Aaron. I've put it in the Carb FAQ. 

Now I need someone who has actually tried the solder/JB Weld route to post results.

Steve

PS Aaron - don't remove the image from your host or the FAQ won't work for future readers!

[Brantley]

Just use fuel line that fits directly over the tube. It really works. I had a CB350G that PISSED fuel from the overflow on one carb after sitting for a while during a top end rebuild. I told an old-timer at a local shop that I wouldn't reveal his secret so you didn't here it from me...

[dusterdude]

i had the same issue and i did use jb weld,however i cant say for sure yet if that fixed em.i still had a leak until i discovered last week that my petcock was leaking internally.i ordered a new one last week,so we`ll see how it goes.

[hcritz]

I have soldered several through the years...never had a problem with that.
Not sure how long the JB weld would hold up submerged in fuel all the time???
the fuel line sounds like a good Idea if the tubing is totally fuel resistant...
Maybe some of the small stuff like weedeaters use...have to make sure it doesn't touch the floats and cause them to stick.

[75750SS]

I've used Silver Solder on the brass pins that hinge the floats to the posts.  I just wicked the tips so the pins would stop slipping out.  This was done last year and no problems so far.  Just make sure you use the correct flux.  It really makes the solder flow.

[snyquist53]

bingo!!!!   thank you thank you thankyou.  the drips were driving me nuts.  i looked and mine has them also.  now i can repaint my block.

[Aaron J Williams]

I went to the parts store this morning and got some shrink fit tubing, cut it to 29/32nds, roughed up the tubes with sandpaper and shrunk the tubing on. Both bowls have been sitting full of fuel all day with no problems. Tonight i'm going to put them in my carb acid tank overnight and see what happens. If they survive that i'll post pics tomorrow.

[dusterdude]

cool idea,i hope it works

[Bodi]

"I've used Silver Solder on the brass pins that hinge the floats to the posts"
OK, I don't understand what this is for. The pins are captive once the bowls are on, aren't they?

[Aaron J Williams]

Ok, here's what I came up with for a solution. I took a piece of shrink tubing for 18 to 20ga wire and cut it to 29/32nds and put it over the cracked brass tube. After shrinking it on I put it in carb acid for 1 day to see how the tubing would hold up. The acid swelled the tube enough to slide it off the brass but after a couple of hours it shrank back down and was tight on the tube again. I then put the bowl back on the bike and after sitting in gas for 2 weeks it shows no sign of degradation. I think this is a viable alternative to JB weld or soldering and it looks a lot cleaner too!

[kayaker43]

You mention carb acid? What are you using to clean/brighten carb parts?

[Aaron J Williams]

The stuff I'm using now is Berryman B9 Chem-Dip but I prefer Gunk Hydro-Seal. It is right around $100 for a 5 gal. bucket and I got it from my local auto parts store. Here's the chemical breakdown:

Methylene Chloride 55-65%
Cresolic acid 10-15%
Xylene  20-30%
Sodium Bichromate <4%
Ethyl Benzene <6%

It works pretty good and lasts up to 5 years depending on how many carbs you clean but if you use it, be careful it is nasty stuff to breathe or get on your skin.