Model b wont start need help

The backfiring sounds like a timing issue (to me). Are the gears in the mag timed correctly? The gears (rotor) inside the mag must be timed correctly or the points will not be opening at the time the rotor is contacting the terminal in the cap.

Are you using a Fairbanks-Morse or WICO mag?

If you are using a FM mag, #1 wire should go in the 10-11 oclock position, with the #2 at 2-3 oclock, #4 at 4-5 oclock and # 3 at 7-8 oclock.

If it's a WICO, (I believe) everything is moved clockwise one position so the rotor (pointer) is pointing to the "window" in the cap (I'm not that familiar with a WICO mag) I believe the #1 cylinder will be at 2-3 oclock.

My advice is to turn the engine until it is on the compression stroke. Have someone watch the hole in the left side of the tractor for the "FIRE" mark (forget TDC and time using the impulse). Stop with the "FIRE" mark at the pointer on the compression stroke. The slots where the mag mounts should be nearly horizontal (slightly above horizontal on the engine side). Turn the mag backward until it lines up with the slots. Install the mag. The rotor should be pointing at the #1 pole in in the cap.

If the gears (rotor) inside the mag are not properly timed, you will continue to get backfiring and you could hurt yourself cranking it if it kicks.

I think the cam timing is off, we had a short break in the weather so I pulled the carb and cleaned it made sure the float was working properly. Then I followed the spark it fires on 1 but the intavalve starts opening after it fires and the other valves seem to be off. Hopefully the weather is good tomorrow I'll pull the front cover and see what's going on in there hopefully this is the problem. Also he has a ball valve on the gas tank with a inline filter instead of the glass bowl. I found it in the ahead but the lines are missing. So could this be the reason for over fueling?

CTuckerNWIL wrote: Your spark is on the exhaust stroke.  You are off 180 degrees.

There's more askew if the exhaust valve wasn't open as the piston traveled upward before ignition, yet started to open after ignition. Both valves should be closed as the piston travels upward and remain fully closed for the entire downward stroke. It's almost as if the engine was turning backwards - if I understood the description correctly.

Sorry I got the intake and exhaust valves mixed up and compaired it to the old one it's the second valve from the radiator that opens after it fires on cyl 1 so it was the exhaust valve opening again sorry I'm new to this I ordered a allis chalmers manual so once that comes in I'll have lots of info on this tractor haha. I didn't realize the valves switch from cyl to cyl that was my mistake. The weather is suposed to be nice tomorrow so I'll work on pulling the front cover and check cam timing. I've never done it so any pointers or tips be for I tackle it? It seems the radiator, starter pully and all that needs to come off before the cover can come off anything else?

Yes there are 2 TDCenters. One is the compression stroke and the other is the exhaust stroke. All 4 cycle engines have the timing mark show up twice for each cycle .
 All you should have to do is switch the plug wires out 180 degrees and start it up.

you have nothing to lose by switching wires....and its a lot easier than pulling the cover...try it....just keep them in order....sounds like you are 180 out.

I think that is right 4312. Easy way to be sure you are not off 180. Leon

Glad you are making progress. So now you know about TDC on the compression stroke.
I read the thread, maybe I didn't grasp it all, can you please answer some questions?

1) Do you have the hand crank?
2) Does it have an electric starter?
3) What make and model carburetor?
4) If yes to hand crank, how tough is it to crank over?

   If the engine was rebuilt wrong and the bearings are
   not right, when you do get it running it may hand grenade.
   Try to tell us how much effort to crank.

I think it's a zenith I'll look tomorrow and let you know!

It sounds good that you can turn the engine easy with no plugs. That engine has a tricky situation with bearings and shims and clearances.
It would not be too hard to get a bearing in a bind, which equals heat, which equals disaster. I would say you are cleared for takeoff.

It has been my lifetime experience that the Champion J8 was a random headache. I went out of my way to get Autolite 295's for my tractor.

Your B has no electrical system? No starter, no lights, no generator?
Does the flywheel have a ring gear, does the torque tube have a hole for a starter? I don't know the production history of what got in as standard when, plus there was a war on you know, maybe they reverted back to hand crank only for a time.

You got to know that a carb and the needle valve/seat problems can drive ya a little batty. Just as frustrating as the spark quest.
And then we will have a spat over inline filter and rubber hoses vs. original fuel bowl and steel lines. Some carb rebuilder outfits send an inline filter with each rebuild and a note saying "use this filter or warranty void". I think I read you do not have the stock fuel bowl shutoff? My advice, add an inline gravity type filter now. Then you will only have to take apart the carb for cleaning just once.

Well got the carb all straightend out and it started second crank no smoke no rattles or leaks she purrs like a kitten. Took it up and down the property a few times with no issues till it ran out of gas. Got a few errands to run then I'll get gas and run it some more. Thank you guys for all your help.

And yes no electrical system no lights no e start hole for the a start it's a 1942 hand crank only

DougS wrote: When everything is working you can pull the mag and turn it 180. Then put the wires back where they were originally. Retime the engine with a timing light and you'll be good to go.

WHY! The wires are were they need to be the way the mag is mounted. It doesn't matter one bit if he leaves it that way or wastes time going thru this all again.

It's alive! Very good. Another B stirs the dust.
I bet your status went up a few notches with the father in law.
Oil pressure good? Check the valve lash after running some.

Glad you got 'er running again!! The "B's" are nice little tractors....

Hamblin I don't know how it can happen but the shaft to the mag gets bent. I know, it can't happen, but it does. You might check that, and at the same time check the bushings. If there is to much vibration it can screw up the timing. But I still think it's in the mag. timing.