Carb problems made worse due to colder weather??

Sat Dec 18, 2004 3:48 pm

I've pretty much got my 51 Cub restored. I'm running with a temporary fuel tank till I get the hood painted in the Spring. I rebuilt the carb as part of restoration, and first started it up several weeks ago. It ran fine, driving it around for a half hour or so on several occasions. One thing I did notice is that it was running much too rich, despite what I could do with the idle screw. The new plugs (I had changed to hotter plugs) quickly had become carboned even after only an hour of running. I had set the float up as per Lurker's guidelines (measurement dry), but after seeing the carbon on the plugs I figured I would now have to try the wet level method, thinking the float could be too high and thus causing the over rich condition. I hadn't gotten to that yet, because the Cub had been running smoothly.

I began experiencing problems running my 51 Cub today. The only difference is that the temperature today was about 35 F, compared to the 70 F degrees it was when I was running well a couple of weeks ago. Of course this was the time I wanted my kids to finally get a chance to drive the machine that had been apart for two years!

I couldn't keep it running. Every couple of minutes it would just quit, particularly under load. I could restart it, it would run for a minute or so, and then quit again. Nothing else had changed, same gas (even added dry gas just in case). Is it possible that this is the same problem made worse by the colder temperature?

I would appreciate your suggestions.


Sat Dec 18, 2004 4:53 pm

Paul sounds like dirty fuel as you describe it. I had fine rust or some such in my 63 low boy. Drained out almost all the gas. Ran it through a coffee filter. PUT in a gallon at a time ran that through the filter. did this 5 or 6 times till there was no more crud. I took a piece of telephone inside wire and poked out the tube in the carb. cleaned the carb bowl. carb screen and the glass bowl bowl screen. No more trouble. ran like a top.
I was able to keep it running with the choke. The problen happened while I mowing in a field aways from the garage.


Sat Dec 18, 2004 4:59 pm

I think you have two problems. The first was the over rich and the next was starving for gas. Let us know when you get it running and we will go from there.


carb problems

Sat Dec 18, 2004 5:13 pm

I had a similar problem, make sure the fuel tank you are using can get air in to replace the fuel going out of it. Also this time of year the fuel companys switch to winter blend fuels, old summer blend fuels have a hard time vaporizing this time of year. Just adding fresh fuel should help.

Sat Dec 18, 2004 6:45 pm

I think Mike probably hit it with the tank not being able to vent. If you are using a small (gallon or less) type tank as a temporary, it cannot vent quickly enough to allow fuel to meet the demand of the engine. Try loosening the cap and see if it will run. You can then concentrate on getting your carb set correctly.

Sat Dec 18, 2004 10:48 pm

Thanks for the suggestions. I will try them next week and report back.


Sun Dec 19, 2004 10:24 am


Just my two cents...

I had a similar problem in that I repainted my Cub and was running fine for several months until one day, Henry'd fire up but as soon as you put him under load or even increase the throttle more than half way, he'd quit. The culprit was small paint chips that plugged the strainer orifice. The action of unscrewing and rescrewing the gas cap scraped off tiny little pieces of paint which would fall down into the tank. I blew compressed air back through the fuel line and that did the trick. Of course this hasn't solved my problem in the long run since the particles are still in the tank but I'm running like a top again.

dirty tank solution

Sun Dec 19, 2004 2:16 pm

I also had a tank with some rust in it that would cause fuel blockage. Someone suggested to me that I add a pound of sharp/fine gravel (aquarium store) add some muriatic acid (forgive my spelling) and shake the tank until it is shiny inside.

Since I did not want to pull the tank off right now, I instead removed the fuel filter from the bottom of the tank. I tapped out the hole a little larger and deeper to (tightly) accept a two inch long 5/16 OD stainless steel tube. Before I shoved the tube into the threaded fuel filter housing, I drilled several small holes in it starting about 1 inch up.

It seemed to work real well. The rust and other fine debris settled below the new tube. The only problem is that I can not use the last inch of fuel in the tank - big deal!

Too Bad IH did not use a much larger tank outlet opening. I think the Ford tractors have a sock/filter that screws into the bottom of the tank.

Any thoughts ?

Sun Dec 19, 2004 2:43 pm

I saw the remains of a screen in the tank when i bought my 63 Low Boy. I was at least the third owner so I have no idea if it was stock or not.


Sun Dec 19, 2004 7:04 pm

Don't know if all of them did or not, but many of the original IH tractor sediment bowls had cylinder shaped scrrens sticking up into the gas tank. They seemed to break off in a few years, I assume from vibration.

Tue Dec 21, 2004 8:46 pm

I removed my sed bowl all together, repiped the entire line with copper tubing and installed an automotive fuel filter and has been working great for two seasons now. Big troubles! I was told I would have a flow problem but I haven't yet, on the contrary, the fuel flows well and will use every drop in the tank.

Tue Dec 21, 2004 11:39 pm

If you use the right filter it is ok. Some of them were designed for pressure systems and have a problem with getting enough fuel through. I've had one on my 48 for 17 years (not the same one). Might want to keep an eye on the copper. With age and vibration it soemtimes gets brittle.