Leaky Linkert

Linkert related issues
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Mark44
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Leaky Linkert

#1

Post by Mark44 »

I recently bought a Linkert M-74B carb that I went through, completely taking it apart and cleaning everything, and putting in one of Cotten's Durable floats. After putting it on my Panhead and getting it dialed in, I noticed that it was leaking gas.

After that, I took it apart, and checked that the float valve was seating correctly. When I put it together, I put in a new valve seat and solid needle valve. After taking it apart this time, I noticed that the float wasn't as tight as it should be, and tightened the little screw down pretty good. I also reinstalled a Viton-tipped needle valve that had been in the carb before. The float is level in the bowl, and set to 1/4" below the rim. After reinstalling the carb, it is still leaking, apparently from one of the vents indicated by the arrows in this image. The 1" float bowl screw is very tight, and besides, the carb is wet with gas well above the bottom of the float bowl.

One of the vents is the downward-opening vent on the Power needle; the other vent is a horizontal opening in the middle of the carb. The gas seems to be seeping out of one or the other of those openings. Both vents are above the level of the float, so the only explanation I can come up with is that the needle valve isn't shutting off the fuel, and allowing the fuel level to rise up to where it comes out the vents. I checked both of the needle valves by turning the float bowl upside down and blowing on the gas inlet. They both seemed to seal just fine. The Durable float I'm using is brand-new, and it's cocked a little to the left in the float bowl, but checked only by eyeball. I can't imagine that it's hanging up on the side of the float bowl.
IMG_1075.cmp.jpg
The image is of my other M-74B, which is what I was running before I bought the one that is leaking. I'm going to put the original carb I was using before back on, and try to figure out what's going wrong with my "new" Linkert.

I'm really scratching my head trying to figure this one out. Does anyone have any ideas for why I'm getting gas seeping out? It's not leaking very much - just enough that the lower part of the brass carb body is wet.
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Bigincher
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Re: Leaky Linkert

#2

Post by Bigincher »

Sometimes when you put on a new 'dry' carburetor, it will flood out and leak like crazy. Why? Because the float bowl is empty and the float is all the way down, and it hangs up on the carb main stem. A few raps with a screwdriver handle (or rapping tool of your choice) will free the float from hanging up, and allow it to come up and shut off the fuel supply as it's supposed to. I would try that before getting too crazy about tearing it apart.
Also, I've had better luck with the solid valve needles as opposed to the Viton tipped.
Mark44
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Re: Leaky Linkert

#3

Post by Mark44 »

Bigincher wrote:Sometimes when you put on a new 'dry' carburetor, it will flood out and leak like crazy. Why? Because the float bowl is empty and the float is all the way down, and it hangs up on the carb main stem. A few raps with a screwdriver handle (or rapping tool of your choice) will free the float from hanging up, and allow it to come up and shut off the fuel supply as it's supposed to. I would try that before getting too crazy about tearing it apart.
Also, I've had better luck with the solid valve needles as opposed to the Viton tipped.
I've been running the carb for several months, and just discovered that it was leaking. When I went through the carb, I replaced the Viton-tipped float valve with a brand-new steel valve and brass seat. Just a few days ago, when I took the carb apart, I switched out the steel float valve with a Viton one that I had been running for several years, but that looked to be just like it did when I put it in -- new swelling or other deformation.

The consensus seems to be (including a PM I received) that somehow the float is hanging up. I'll give the float bowl a few raps, and see if that takes care of things.
Mark44
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Re: Leaky Linkert

#4

Post by Mark44 »

Update: I think I have things squared away now. It seems that the float was making contact with part of the bowl stem on the low speed needle side. Another member advised me to use a dry erase marker on the parts of the bowl stem that protrude, and then put the bowl back on. After turning the assembled carb upside down a few times, I found a spot on the bowl stem where the marker had been rubbed off. After adjusting the position of the float in the float lever, the float doesn't contact the bowl stem any more.

I installed the carb on the bike and attached the fuel line, and opened the fuel shutoff to fill the bowl. After sitting all night, no leaks, no seeping (fingers crossed).

Thanks to all who contributed advice!
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Re: Leaky Linkert

#5

Post by Excalibur »

Could it be the float pivot is worn? I made a new pin for mine recently. I used a piece of twist drill shank. See detailed pics on my blog if interested. Go to Linkert carb page..
Mark44
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Re: Leaky Linkert

#6

Post by Mark44 »

Excalibur wrote:Could it be the float pivot is worn? I made a new pin for mine recently. I used a piece of twist drill shank. See detailed pics on my blog if interested. Go to Linkert carb page..
I put in a new float lever, and the pin seemed to be in pretty good shape. The problem seems to have been the position of the float on the float lever. The hole in the float lever allows for different positioning of the float -- if you get it in the wrong place, the float can hang up on the carb stem.
Lionel
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Re: Leaky Linkert

#7

Post by Lionel »

I used a ball bearing ,dropped into the opening of the seat and gave it a rap withe a punch and a hammer ,this corrected the shape of the seat ,I then used valve grinding compound to lap the steel needle to the seat , I finished the lapping using tooth past as a compound. Tested by applying about 3psi.to the fuel inlet ,which it held.
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