9n runs good until warm

9n 12v just bought it. It will start fine and run good for about 20-30min. then you have to choke it and keep choke on to keep it running. but gradually worsens and stalls.

It takes three things for an engine to run: spark at the right time, compression, & fuel in the right mixture. For the moment, forget about compression & concentrate on narrowing the problem down to spark or fuel.


There are three very important tools you always need to have in your N tool box: a 3 inch piece of wire w/ alligator clips on each end, an old spark plug w/ the gap opened to at least 3/16” ( ¼” is better) and a 7/16 box end wrench. (see tip # 50 at the link below) And, you really do need a working ammeter on the tractor; it is a very important diagnostic tool. With these tools, you can quickly narrow down most N problems to spark or fuel.

Next time it stops, check quickly for fuel then spark. When I say quickly, I mean get off the seat, grab the tools & do it right then. Do not wait a minute or two. First, check for fuel. Get a can & put it under the carb. Remove the bolt in the bottom of the carb; as long as the fuel is turned on, you should see gas flowing out of the carb. Let it run for at least 30 seconds. If it’s a dribble, or runs for 5 seconds & stops, or none at all, you have solved half the problem: it’s fuel related. If gas flows well out of the carb & only stops when you turn it off at the sediment bowl, chances are very good it’s not a fuel problem. So, next, turn the key on, crank the engine & look at the ammeter. What is the needle doing? Does it show a constant discharge, no movement at all, or does it move back & forth slightly? Next, get the old plug, ground it to a rust & paint free spot on the engine, turn the key on & crank the engine. If the spark jumps the 3/16” gap, you probably don’t have a spark problem. If it won’t jump the 3/16” gap, you have a spark problem. If the ammeter needle shows a constant discharge, or doesn’t move at all, that also tells you that you have a spark problem. Jump the ignition switch w/ your jumper wire & see what happens. If it runs, you found the problem. If it doesn’t have spark after you jump the ignition switch, post back for more info on further troubleshooting. (and do not forget to turn the ignition switch off; see tip # 38)

If it does not have gas coming out of the carb at a steady stream w/ the bolt out for at least 30 seconds, you have a fuel problem. First, remove the gas cap. Your vent could be clogged & it vacuum locked. If that doesn’t work, tap the carb bowl w/ a hammer handle in case the float is sticking closed. (don’t whack it w/ the head of the hammer; you can crack the bowl). If you still don’t see gas flowing, the N has three fuel screens; one in the brass elbow, one in the top of the sediment bowl & one on the stem of the sediment bowl in the gas tank. Check the screen in the elbow & the screen in the top of the sediment bowl. (don’t worry about the one in the tank) Both probably need to be cleaned. If you have the fuel knob turned on all the way, & 1 gallon or less in the tank, it may be trying to feed off of the reserve inlet which is probably clogged. Only open it 2 full turns. Put at least 2 gallons in the tank. (and do not forget to turn the gas off; see tip # 9)

There are ways to check for spark & fuel that work & ways that don't. For example, having gas to the carb is nice, but having it past the float is what counts! That’s why removing the bolt in the bottom of the carb is the way to do it. And, same thing w/ spark at the plugs. Some folks think that checking for spark means pulling a plug wire off & looking for one. Well, it's the distance the spark jumps at the plug that gives you the info you want. It takes about 17kv to jump a 3/16" gap & 22kv to jump ¼” in the open air, so that's why you need to use a spark plug. Or, a store bought plug checker (on the left in the picture). Remember, it’s 14psi outside of the engine & about 90psi at a 6:1 compression ratio in the cylinders & compressed air creates electrical resistance, so you really need the 17-22kv to fire the plugs when the engine is running.

Post back w/ results or other questions.

50 Tips

Will......there are 4-common "runtime issues" with the 4-nipple frontmount distributor. Which one is yours???

1) runs fer about 1-min and quits; restarts in about 5-mins. BAD condenser, NOT yer problem
2) runs fer about 5-mins and quits; restarts in about 10-mins. CLOGGED fuel tank filter, NOT yer problem
3) runs fer about 1-hr and quits; restarts in about 4-hrs or overnite cooldown. BAD squarecan ignition coil, NOT yer problem
4) runs fer about 15-mins and quits; restarts in about 30-mins. BAD weaksister ignition switch. Sound like yer problem???

The internal contacts gitt gunked-up and cause weak sparkies that will run on choke enrichment until the sparkies can no longer sparkle the rich gas and stalls out. You doubt? jumper yer weaksister ignition switch with jumper wire and alligator clippies. NEW 2-wire ignition switch, $12 (cheap) ......Dell, yer self-appointed sparkie-meister

I had the same problem with my 8n side mount.I switched it to 12v and installed the resistor that was inclued with the alt. kit and I should'nt have because I switched the coil to 12v.The resistor is to reduce the voltage from 12v to 6v to your coil. Check to see if it could be possible that maybe there could be a resistor installed between your key switch and your coil and check to see what volt coil you have.

thanks pete(f1)due to 5 foot snowdrifts not mutch work has been done on my tractor,but we did tunnel to it i did not see any resisters with the exception of the resister ignition switch I was unable to check coil voltage because i fouled the plugs on last attempt to get her started. I will get back to it once the shoveling is done the drift was about 200 feet long.Thanks again for the suggestion.

thank you dell(WA)not much work has been done on my tractor since your reply due to 5 foot snowdrifts about 200 feet long between me and the ford,but we did tunnel to her and dig her out so when they clear the road I can get some plugs. I managed to foul the sparkies after rebuilding the carb and trying to dial it in before the drifts came.Thanks again for your suggestion I will check it as soon as we are running again.One more question Is it ok to to leave jumper on while running or are you to just check spark?

thank you Bruce(VA)not much work has been done on my tractor since you replied to my qustion due to a 5 foot snow drift between me and the ford about 200 feet long,but we did tunnel up to her and get her un covered.Ichecked the ammeter and it is doing nothing,I know it was working but there was a small electrical fire from rewiring the head lights it was my fault not thinking and hurrying against coming snow storm.I did not notice the ammeter not working until checking what you had suggested.I cleaned the tank and settlement bowelassembly and screens and rebuilt carb,all had a lot of dirt,afterwards while trying to dial in carb I fouled the plugs and cannot get out for more our road is still blocked.After I get plugs I will try jumping the ignition and check the spark thank you for your advice.One question should I jump the ignition after it tries to die out?

You need to find where it lost battery voltage that caused it to stop running. You can't do that until it actually stops. It might not be your ignition switch. As soon as it stops, jump the switch.

Post back if you have any other questions.