IH Carb Question

[Eugene]

Hi Eugene, Not sure how to post a question on the forum, so hence the pm.

I have an IH carb on my '48 cub. On looking at the plugs yesterday I noticed the electrodes were very black. Could the mixture be too rich, and is there any way to adjust to make it leaner?? Or would the cause be that the cub is not being worked enough, and is only taken out for an occasional spin round the garden.?? The cub starts up first time every time even though it could be months between start ups, and runs like a swiss watch once she is going for a minute or two.

Bernard, Donegal Cub.

[Smokeycub]

I would suggest it needs run a bit harder to help burn off the carbon/soot on the plugs.

Or would the cause be that the cub is not being worked enough, and is only taken out for an occasional spin round the garden.??

This would be my guess.

What plugs are you running? If you don't plan on much more than a fast idle and little load you may consider a hotter plug.

[Donegal Cub]

New Champion 16, Wagon 19 kindly took them to me on his last visit to Ireland.
Bernard,
Donegal Cub.

[bob in CT]

That is a cold plug, or a plug suitable for hard work. I run them in my mowing tractor. D-21 may be more suitable for light duty use.

[Boss Hog]

Hi Eugene, Not sure how to post a question on the forum, so hence the pm.

I have an IH carb on my '48 cub. On looking at the plugs yesterday I noticed the electrodes were very black. Could the mixture be too rich, and is there any way to adjust to make it leaner?? Or would the cause be that the cub is not being worked enough, and is only taken out for an occasional spin round the garden.?? The cub starts up first time every time even though it could be months between start ups, and runs like a swiss watch once she is going for a minute or two.

Bernard, Donegal Cub.

I would start with a complete tune up wires and the rest, and a carburetor rebuild too, the stiener kit

Oh on a somber note , check the oil bath cleaner, may need cleaning

[Smokeycub]

D-21 may be more suitable for light duty use.

[Eugene]

IH carburetor has a tendency to run rich. With not knowing any more I would suggest leaving things alone since the tractor starts and runs fine.

Could be several causes for soot covered spark plugs. Wrong heat range of the spark plugs, previously mentioned. Engine operating temperature, not getting hot enough. Fuel level to high in carburetor. Carburetor main jet orifice to large.

[SundaySailor]

"Carburetor main jet orifice to large."

There was some discussion here a few years back with Rick Prentice and some others getting rather deep into the discussion.

Apparently there were at least three different jets with different bores & associated parts that would cause the tractor to run better/poorly.

I don't remember when the thread occurred, perhaps one of the other members can remember back that far.

Yes, Eugene, I too have CRS.

It happens to the best of us.

[Eugene]

Bernard:

If you want to post a new topic, select the forum. Then, a bit down on the left side, click on new topic. Type in a topic name, then type in your message. Actually it;s pretty much the same as posting a reply to a previous post.

The only thing I have found is that I need to copy my message before submitting for preview or final submission. Some times my message disappears off into never never land.

Eugene

[Bob McCarty]

Sunday Sailor is correct about there being differences. The main jet, discharge tube, and bleed are calibrated to match each other. If the part # of the carb still shows on the edge of the flat part opposite to the gas intake, you can tell which parts should be in your carb. If you include the numbered LoBoys that had the IH carb and stationary engines, there are probably 6 combinations. The aftermarket kits are "universal", and some of the aftermarket jets do not even have the correct orifice size as the OEM. That being said, It doesn't seem like mixing parts causes any obvious and serious fuel issues, at least not frequently. I'd suggest changing plugs first and seeing if that helps.

Bob

[SundaySailor]

Here are some of the previous topics regarding jet bore sizes: http://www.farmallcub.com/phpBB2/viewtopic.php?f=1&t=50223

http://www.farmallcub.com/phpBB2/viewtopic.php?f=1&t=74036

http://www.farmallcub.com/phpBB2/viewtopic.php?f=1&t=10754

I'm sure there are more, but these cover a lot of information.

I ran into a similar situation where I had mismatched parts. My cub ran very poorly until I read some of these articles and was actually able to get the new correct parts for my IH updraft carb.

I later sold that carb and purchased the newer reproduction carb of which I've had for years now, and it's still running great.

[Jim Becker]

Don't look for problems that aren't there. In this case, I'm sure that messing with the carburetor will just cause problems.

Your plugs are too cold for the way you are using the tractor. You need Champion D-21 or equivalent in another brand. Black is the normal color for deposits on plugs. It is just a matter of whether so much has accumulated that it causes fouling. The remedy is hotter plugs or working the engine harder.

The gray color that showed on plugs back in the old days was from lead deposits. With no lead in modern gas, all that remains is the black that was mixed in with the lead. All the old documents that talked about proper color of spark plugs is obsolete.

[bob in CT]

I run D15Y Champions in my tractor for mowing. It gets worked hard for over an hour at a clip in hot weather. The plugs are a nice brown color with no soot. This winter I had my tractor in the shop to rebuild the hydraulic system. Short runs at no load and fast idle for testing the touch control and the plugs were black. I put in D-21's for the time being, but I will change them back to the colder plug if the grass ever starts growing here (still a little snow out back).

[Donegal Cub]

Thanks Eugene,
Also thanks to you guys for all your advice. I will do as Jim Becker advises, ie do not look for problems where there is none. I was wondering is the screw on the top of the carb a mixture screw??
Thanks All
Donegal Cub.

[Rick Spivey]

The screw on top is a mixture screw. It adjust the air flow, not gas, so out to lean, in to richen. I like to get a smooth idle with no black wisps out the exhaust, and then adjust slightly until I get a smooth fast response to full speed. It should not hesitate or stumble when I blip the throttle from idle to full speed.