Topic: Have I solved the problem of cracked overflow tubes?!

[davis96]

So if you have cracked overflow tubes and have searched the forums for a solution, you are probably familiar with the heat-shrink tubing fix which has been done by others including myself in the past. The problem I have experienced (as have others) is that, inevitably, the shrink tubing soaks up gas, expands, and thus loses its effectiveness.

My solution is really just an addition to the old fix. I found, at a local Ace Hardware, that brass tubing is available in a number of minuscule sizes. It happens that the tube labeled 5/32" (which is the outer diameter) fits quite snugly over a cracked tube which has been covered with regular 18g electrical heat shrink.



Hobby stores (i.e. hobby lobby) also often carry these brass tubes. They are cheap, I got a one foot piece for $1.39.

I haven't re-installed the carbs yet, but the theory is that the heat shrink will not be able to expand because of the brass tube. I will update after I test the solution, but I really can't think of any reason why it wouldn't.
-Davis

[Tugboat]

Nice work!

[phil71]

heat shrink will disintegrate.

[Killer Canary]

In the past I've used fuel line tubing for nitro r/c planes.

[TwoTired]

Why not solder up the crack in the brass tubing?  Acid core solder has always worked for me.

FYI: R/C planes now have two types of tubing, btw.  One type for pump gas, usually Tygon, and the other for alcohol based fuels.  Each is unreliable in misapplication.

I recommend you put a piece of the heat shrink tubing in a container with gas, then check the tubing after a month of soaking.  You'll either be happy or sad.

Cheers,

[LesterPiglet]

Out of interest, does anyone have a theory why these tubes crack? Is it age/mileage related?

[Killer Canary]

In my case it was water getting into the bowls and then freezing over winter because of numbnuts pre owners.

[davis96]

Why not solder up the crack in the brass tubing?  Acid core solder has always worked for me.

Because I (and many others) don't have the requisite skill or equipment (I have been told that my little electrical soldering iron isn't powerful enough)

I recommend you put a piece of the heat shrink tubing in a container with gas, then check the tubing after a month of soaking.  You'll either be happy or sad.

Already did, as the last time I attempted to fix the problem (about a month ago) I used only the heat shrink. It worked for a bit. But like I said, it swelled up and became loose. It did not, however "disintegrate" as phil71 (above) said it would. The heat shrink was still there, in one piece; it had simply deformed a bit, rendering it useless.

[BobbyR]

You soldering iron or gun has the heat, you do not want too much heat. If you can search the site a lot of guys have used the brass tubing. Some I think soldered the tubing in place which should be permanent. I think even JB Weld would be better that the shrink. Good idea though, but there are better solutions.

[lucky]

Out of interest, does anyone have a theory why these tubes crack? Is it age/mileage related?

Just a guess.
I think it mostly east cost or cold climate bikes.
I think water gets in the tube and then expands when it freezes.
Never heard of it happening  on the west coast.

[ekpent]

I have had very good luck with this product in carbs. Think if you 'glued' the brass tube on with this as a filler instead of the rubber it would hold up very well and long.  http://www.biosafe-inc.com/sealall.htm

[killersoundz]

I had two cracked overflow tubes. Managed to solder one up successfully but the other one not so much, it's a little more damaged. I just purchased a replacement bowl on ebay for $16 including shipping

[TwoTired]

Why not solder up the crack in the brass tubing?  Acid core solder has always worked for me.

Because I (and many others) don't have the requisite skill or equipment (I have been told that my little electrical soldering iron isn't powerful enough)

What wattage is your iron?  If the tip can melt solder, you may only need to increase the tip's mass to heat the pipe enough.


But, there is the proper tool for the job, thing.  So rather that get the right tool, you are going to experiment with materials that you already know don't withstand fuel?

While I like creativity.  There is a practical and correct function side of the issue to consider. 

Anyway, I never found soldering to be that difficult a skill to learn.  I know I was soldering while still in high school perhaps before.  It's hard for me to imagine not being able to solder.

Good luck!

[fmctm1sw]

I used a burnzomatic torch to heat mine when I soldered it.  My bike is a Florida bike and had a cracked tube...

[davis96]

Re-installed the carbs and they hold fuel beautifully, its the first time in a while my bike has been leak free. I will let you all know if any leaks appear.

I could have soldered the cracks I guess, but it seems like a hit-or miss solution for the amateur solderer (and I am worse than average at soldering, for whatever reason). The only thing that happens when the heat shrink is exposed to fuel is expansion, just like float bowl gaskets. And just like the gaskets, they dry up and shrink after being exposed to air for a while. However, when prevented from expanding, it seals nicely.

Whether or not it constitutes a "proper" fix is certainly up for debate. I'm sure there is someone out there who would swear up and down that the only proper way to fix a cracked float bowl is to buy an NOS Honda unit.

Thanks guy,
Davis

[Dimitri13]

My heat shrink has lasted nearly a year with no signs of giving up.

[BobbyR]

Time will tell, keep us posted.

[davis96]

Time will tell, keep us posted.

Spent a few days on the bike without any significant leaking (using an aux fuel tank with no "off" switch for purpose of vacuum syncing, so they were supplied with fuel constantly). Due to mysterious air leaks, I was forced to pull the carbs off again today. While they're off I'll pull the bowls and check on the fix.