Topic: hairline crack in overflow tubes.

[outaline]

Hi everybody. This is my first post, although I am a regular visitor to the site. Two of my carbs on my 73' CB 500k continually leaked gas, even after I overhauled the carbs and checked the needles and float height. The bike runs awesome so I didn't think the float height was the problem. I took off the float bowls and discovered a hairline cracks in the overflow tubes on both of the flaot bowls that leaked.

My question is - how the hell do I fix this. Do I need to buy new float bowls?

Thanks in advance for your opinions!

PS: Has anybody put on an aftermarket carb for the CB500K?

Tony

 

[jaknight]

HEY OUTALINE,

     Welcome aboard!! I do hope you enjoy the ride(s)!

     Someone will show up to give you some good answers to your question.  I do know that you can buy new floats, they are still available  - - -  Like at David Silver Spares, possibly Old Bike Barn and several others.

     As for repairs........... I know that someone will come in with some good answers.

     Meanwhile, kickback, scoot around here and enjoy the roads........

     ~ ~ ~ jaknight ~ ~ ~

[Magpie]

It seems that's quite common. My "fix" was new float bowls from the bike salvager. Quick and easy.
Cliff.

[KB02]

A buddy of mine had this happen on his CB400T. There are two fixes that I know of.

SOLUTION #1 - (The one that we used) Find a used set of carbs on ebay that have good tubes and simply use those bowls to fix the problem.

SOLUTION #2 - Get some plastic or rubber tubing, that will hold up to gas, that just barely fits over the overflow tube. Find some kind of sealant that also works with Gas (I have a tube of some stuff in my garage that I have used in the past with sucess. Any auto parts shop should have something in stock). Coat the outside of the overflow tube with the sealant (lightly, but enough) and slide the plastic (or rubber) tubing (once cut to length) down over the overflow tube. Let dry, reassemble, test, ride, enjoy, go on with life.
   The trick is making sure the cover tube is very snug and the tahe sealant doesn't plug the inside of the overflow. Once the sealant dries, the tube is repaired.

Hope this helps.

[dusterdude]

j b weld and if you dont get it sealed up the first time and dont want to do it again,run overflow hoses off the nipples and run em up above the carb,thats what i did with mine.works good if you are not concerned with gas being in the hoses

[6adan]

I used J B Weld on mine and it is working fine.

[Mark M]

If you raise the overflow tubes to stop the fuel escaping it could have a simmilar effect to blocking the tubes - you could flood your engine. I list a whole tank full into my crancases once, cleans them out nicely but not recomended.

If you still want to try you need to ensure they only gaet raised to the same level as the top edge of your float bowl so that they can still act as an overflow should your float valves be leeking.

[cb650]

We soldered a float once would that work?




            Terry

[outaline]

OK,

So this is the story. First off, thanks to everybody for your input.

The cracks ran about a half inch long so I thought I would pick up some brass tubes at a hobby store and slide them over the tubes and then JB weld the ends. i figured there was less chance of failure if I minimizd the exposed area. As I slide on of the tubes over, the overflowtube breaks off where it comes through the inside bottom of the float. A couple off expletives later I thought - since I got some hobby tubes here, why not drill the hole sucker out and use the new tube. So that's what I did. I still have to JB weld it tomorrow, but the new tube fit fairly snugly into the float body so I don't anticipate any problems.

I'll keep you posted if it works or not.

[nunnik6]

I soldered mine on my '70 750 and they work fine.... nobody is going to see them anyway, so take the easy route:) Just make sure you dont solder the hole shut!!

[mrbreeze]

I for one would like to know how these tubes crack anyway? It sounds like quite a few of you had this problem. What kind of abuse or age makes these tubes crack?

[Juhani]

Hi, i had same problem in one of my carbs. I cleaned brass tube with fine paper 400 or like then used 200w solderingiron and normal solder ment for electronics.
Has worked fine 4 years now. I think these are normal symptoms in old Brass tubes they crack. Plastictube over it would work also if it does not hinder float movement. You can also plug rubber hoses but if your petcock leaks, or its left on, it will fill motor with gas. and you might even bent a rod or something if it hydrolocks at startup.
Cheers Juhani

[dusterdude]

I for one would like to know how these tubes crack anyway? It sounds like quite a few of you had this problem. What kind of abuse or age makes these tubes crack?

my carb guru told me that the moisture in the gas freezes and that of course cracks the tubes,im sure there are other reasons too.

[Raul CB750K1]

It could simply be that the tubes are made out of a rolled piece of brass sheet, and the junction split with time. I've never seen one, but if the split is a straight line then that could be the reason.

As used as I am to work with electronic equipment I would go the "soldering iron" way to repair the cracked tubes or the punctured bowls.

Best regards

Raul

[motorcycleclaude75]

Hello,

I believe I have the same problem for one of my carbs.  There are carbs on Ebay all the time.  I have been outbid several times but I keep trying.  I'm in Canada so shipping can be a bit pricy to get something out of the States but I keep watching.

It's worth a look.  There are several sets on Ebay right now, just don't outbid me. LOL!

Claude

[jtb]

I got a new float bowl for my 750F2 from Service Honda.