What material are carb made of?

I have early Ninja 600 carbs on my kz650, Mikuni CVK32.
I've added overflow tubes to the bowls, but they are leaking.
I used a soldering gun and solder to seal the tubes, but 3 of the 4 are leaking.
I want to try to use a Propane torch to heat the solder up more to flow better into the cracks.

Am I at risk of damaging the float bowls.
What material/metal are the bowls made of?

Engine cases are made from MgAlSi alloy.
Modern carb bodys are made from MgAl alloy and early carb bodys are made from zinc, (Keihin/Mikuni/DelOrtho).
Soldering copper and aluminum together with tin isn´t possible. A 2K epoxy like JB Weld or LOCTITE® EA 3479 will seal the tubes.

I would be careful with a propane torch on a carb bowl but your torch will work fine with that soup.

I would not use a propane torch on these at, best you will probably warp them, then within half a second you stand a good chance of melting them, i would have made up screw in overflows, that way a little teflon tape does the sealing.  

wrote:

Engine cases are made from MgAlSi alloy.
Modern carb bodys are made from MgAl alloy and early carb bodys are made from zinc, (Keihin/Mikuni/DelOrtho).
Soldering copper and aluminum together with tin isn´t possible. A 2K epoxy like JB Weld or LOCTITE® EA 3479 will seal the tubes.

Thank you. I was just asked this. I’m trying to repair a broken web on the crank locator doll. 

Thanks for the replies.
I will keep them in mind if my fix fails.
I am soldering them in as it's been done before with success.
Didn't know about the different metals not being able to solder together.
Will find out how well this holds...


I spoke with a friend and he thought I should be fine using a Propane torch.
I found four bowls on ebay and bought them in case I screw up these.
I fastened a bowl to a piece of wood that already had a small hole to accept the overflow tube.
Held the wood in a vice, and slowly heated the bottom of the tube and bowl, keeping the tip of the blue flame (hottest spot) back from my work.

With a small sweeping action back and forth, not keeping the torch in one spot too long.
Working my way around the tube.
Not much was happening, so moved the flame closer.
This started to melt the solder, but not as much as I thought it would.
Kind of made a ball of the solder.
Didn't think it was working, but a leak test once it cooled showed no leaks.
Put a small piece of rag in the can so I could see any leaks easier.

A leak test on the second carb didn't turn out as well as gas poured out of the bowl.
I forgot to put the drain screw in the bowl.  
Drain screw in and test, no leaks.

I did all four bowls, and each passed a leak test.

Your overflow tubes need to have the tops closed off so there is just a tiny hole open.  Otherwise, when you lean the bike side to side, and hit bumps, fuel may dump down the tubes.

Your overflow tubes need to have the tops closed off so there is just a tiny hole open.  Otherwise, when you lean the bike side to side, and hit bumps, fuel may dump down the tubes.

Good point.
How would you close them off?
Sqeeze them a little?

I've made overflow tubes before and to close off the end I put the tube in a drill motor or my lathe chuck, and then used the dimple in the side of a threading die pressed into the tube to roll over the edges.  The tube was then flared a little on the opposite end and then press fit into the float bowl so there was an interference fit.  No sealing/soldering needed.

I did mine the same as Robs for my CVK34's. I found the procedure on the Concours owners web site. Mine use a different drain screw so my pipes do not exit the bottom, they are blind drilled to a depth of 1.5XOD then press fit in.

As for the top of the pipes being rounded, they do not mention that on the Concours site but did mention the pipe needed to be 8mm above the bowl mating surface. I measured a VM24 float bowl, it uses 4.5mm above the float bowl the pipe having .138" OD and the hole in the top is .058" ID.
I cut my .125" OD pipe (.014" wall) with a small tubing cutter which puts a healthy chamfer on the tube pinching it slightly so the hole is about .090" ID. With the pipe sitting higher and the tubing being smaller OD I figured it did not need the end to be rounded.

Since I press fit the pipes in I would need to remove them to put that round feature on the top and would probably dame them trying to get them out of there.
If leaking on a lean becomes a issue I will pinch the tube ends closed parallel to the lean angle.

The next time I do some I will probably take the time to close up the ends.
 

I measured my CVK34 carb bowls to figure out what kind of lean angle would make gas flow into the over flow tubes.
Looks to be 14 degrees (@8mm above gasket) not sure what that looks like when the bike is leaned over.

I think I am going to have to check and see if this would be a issue, wonder if the pegs are scraping at that point?
My bike is still in storage so I am going to have to wait till I drag it out.

By comparison the VM24 float bowl measures a 6 degree lean angle, but it has the rounded tip and a smaller drain hole.

Put a small diameter steel wire (something solder won't stick to) in the top of the tubes and solder them shut. pull the wire out for a tiny hole.