Gas proof sealing substance for Farmall carb

Zachary Hoyt · Dec 21, 2012

I have developed a leak on the top of the carburetor on my Farmall 300 where the gas line adapter screws into the casting. The casting is cracked in two places (at 11 and 3 o'clock) to the full depth of the threads where the brass looking fitting screws in. I found this out when I tried to tighten the fitting and found that it would not tighten. The bowl of the carb was cracked from water freezing in it before I got the tractor and a very kind forum member sent me a good bowl. The carb is in good shape otherwise and I would like to know if there is any kind of hardening sealer that I can use to repair the casting and secure the adapter that will be gas proof. I know epoxy and JB weld are possible, but I am not sure how the gas would affect them or if there is something else I should try. There is also a mystery screw in a passage that comes into the area where the screen would be if I had one at a 45 degree angle. It is not adjustable when the carb is mounted on the tractor because the head is aimed back at the block. I did not see it mentioned in the manual and I am wondering if I will do any harm by blocking the passage which will probably happen if I am putting any kind of goop in there. Any advice will be much appreciated.
Zach

colekicker · Dec 21, 2012

my dad always used a product that came in a can with a lid brush called Hi-Tack. We'd let it dry before putting gas through it. It never leaked. After it was dry, I would compare it to a taffy sort of substance. It worked very very well. I recommend that.

Royse · Dec 21, 2012

I have one that is held together with epoxy. Working fine.
It was that way when I got the tractor, so I left it.
Can't help with the mystery screw.

Mike M · Dec 21, 2012

JB weld will work

Richard G. · Dec 21, 2012

I have used a JB Weld made especially for gasoline and it worked well.
Richard in NW SC

rrlund · Dec 21, 2012

Permatex is made for use with petroleum.

old · Dec 21, 2012

Had that happen on a Farmall Cub about 10 years ago and I used J-B Weld on it and it has held so far with on leaks

JRSutton · Dec 21, 2012

JB Weld - don't use regular epoxy.

I tried epoxy-ing my float back together one day (it was either that or not cut hay). A couple weeks later when I got my new floats the epoxy had turned to peanut butter.

Granted I may not have let the expoxy cure long enough to immerse it in gas (waited like 20 minutes for the 5 minute epoxy)- but I don't know. I'd stick to jb weld.

notjustair · Dec 21, 2012

I bought some fuel tank repair that was just like jb weld. It was a two part that dries hard as a rock and works great. Use some of that.

MisterT · Dec 21, 2012

(quoted from post at 18:02:03 12/21/12) I have developed a leak on the top of the carburetor on my Farmall 300 where the gas line adapter screws into the casting. The casting is cracked in two places (at 11 and 3 o'clock) to the full depth of the threads where the brass looking fitting screws in. I found this out when I tried to tighten the fitting and found that it would not tighten. The bowl of the carb was cracked from water freezing in it before I got the tractor and a very kind forum member sent me a good bowl. The carb is in good shape otherwise and I would like to know if there is any kind of hardening sealer that I can use to repair the casting and secure the adapter that will be gas proof. I know epoxy and JB weld are possible, but I am not sure how the gas would affect them or if there is something else I should try. There is also a mystery screw in a passage that comes into the area where the screen would be if I had one at a 45 degree angle. It is not adjustable when the carb is mounted on the tractor because the head is aimed back at the block. I did not see it mentioned in the manual and I am wondering if I will do any harm by blocking the passage which will probably happen if I am putting any kind of goop in there. Any advice will be much appreciated.
Zach

That extra screw, going in at angle, isn't supposed to be there. The hole is there because that is where the factory drilled the passage to complete the port that allows gasoline access to the float valve. After drilling that hole, it is then plugged with a brass plug and sealed up. I have no idea why anyone would drill out the brass plug and replace it with a screw, but taking that into consideration, along with the cracked fuel inlet area, you need to find another carb top and toss the one you have on the scrap pile.

Zachary Hoyt · Dec 21, 2012

Thank you all very much. I got a tube of Permatex liquid metal filler for $2.20, it was recommended as being better for the purpose than the JB weld which was also on the rack. I have put it on and am hoping for the best.
Zach

rankrank1 · Dec 21, 2012

Brazing or silver soldering the fitting in would also be a repair option - of course you would have to take it a apart to do it.

That said "Yamabond" is by the far best type of "Permatex similar" liquid gasket maker that I have ever used. "Yamabond" is the liquid gasket maker that Yamaha recommends for use to seal motorcycle 2-stroke crank case halves together when assembling the crank case halves since there is no gasket betwwen them - just the Yamabond. And if you understand a motorcycle 2-stroke crankcase then you know it is pretty much always immersed in gasoline and oil mixture so the stuff has to be stout to withstand that.

Yamabond would be available at your local Yamaha motorcycle dealer but my guess is it is $12 to $15 a tube or so. I retired from the 2-stroke 2-wheelers back in the mid-1990's so it has been a bit since I bought any. Ride 4-stroke ATV now-a-days. Older guys need those training wheels - LOL.

504 · Dec 21, 2012

I use the parts of a gas tank repair kit. I used a single piece of the mat as thread tape, and sealer inside the threads and outside of the carb. It has held for 10 years now.

Gas proof sealing substance for Farmall carb

Zachary Hoyt

Well-known Member

colekicker

Member

Royse

Well-known Member

Mike M

Well-known Member

Richard G.

Well-known Member

rrlund

Well-known Member

old

Well-known Member

JRSutton

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notjustair

Well-known Member

MisterT

Member

Zachary Hoyt

Well-known Member

rankrank1

Well-known Member

504

Well-known Member

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