H plugs

Struggling keeping my H running. Took the plugs out and they were horribly fouled. Cleaned them up and that solved the problem. Ran it for 5-10 minutes full throttle and it started to act up again. Took the plugs out and sure enough they were solid black again. Is that left over and I should clean them a few times or is there another issue going on? New plugs? These are pretty new autolites

Your carb is running too rich. Either from a bad needle and seat, float with a hole in it and sinking or just plain carb adjustment.

Try a plug with a higher heat range but to foul plugs that fast makes me think it's running rich or your air intake is restricted.

Matt, I'm curious about which Autolite plugs you're using. Hopefully, 3116 which are truly non-resistor plugs. 386 and 388 are actually resistor plugs although Autolite's application charts show they are the "proper" plug for the application. Resistor plugs will work, but they make your magneto coil work much harder than necessary which will shorten the life of your mag coil.

Some people hate Champions, but I haven't had any problems with them. I use D21's in my "H" as well as Autolite 3116. 3116 plugs are a little colder than D21 plugs which are fairly "hot" and shouldn't have any fouling issues unless you're running way too rich as others have suggested.

My "H" will run forever at a low idle, but the plugs look horrible upon removal. They'll be totally black with soot except for the actual arcing surfaces between the tip and ground electrode. But they'll still fire. If the tractor is working hard, the black stuff will be mostly burned off, but unless the tractor is working, the plugs will look black.

It might be interesting to see if your "fouled" plugs will spark. Remove them, place them on the engine block, and hook up the plug wires making sure the plug terminals and wires don't short out to the block, then crank the engine and see if the plugs actually spark. If they spark in open air, they'll almost certainly spark inside the cylinder, especially at the low compression ratios of the "H".

WARNING!! - Be VERY careful doing this - there have been some horrible accidents where flooded engines were cranked and raw fuel spurted out of the spark plug hole onto the person turning the flywheel. The fuel was then ignited from a spark arcing to the engine, and you can guess the rest....

If theyre fouling and turning black that often I suspect the carb is way too rich and no plugs can cure that. Id use Autolite 3116 non resistor plugs especially on Magneto ignitions, lean the carb, use shutters etc to get the temp up to at least 170.

John T

Thank you all VERY much for the help. I have been fighting this issues for months...I am getting closer!

I checked as I walked out the door this morning and see it has 388 plugs in it. I will get some 3116 today. I also have no doubt the card is not set right anymore....I have adjusted that thing so many times trying to make it run. I will change back to default settings and try again tonight.

Thanks again for the help, I will reply back with my findings.

Wow, I have new tractor! Started first turn and ran perfect. Adjusted the load down a hair so it ran right. Took it out and ran it for a few miles to get it warmed up and it never missed a pop. Thanks again for the help everyone!

Matt, good to hear she's running well again. Fresh (or freshly cleaned) plugs always seem to help "H's" run and start a little better. And if your magneto coil is a little weak, it might be having problems throwing a spark across those Autolite 388 resistor plugs as things warm up.

I enjoyed meeting you and seeing your neat "H" at CCT a few weeks ago.

Great meeting you as well! If you run across any "H" implements for sale in your travels please let me know!

~Matthew