Back Fire!!

Mon Oct 29, 2012 8:19 am

I was trying to troubleshoot why my tractor would not start and tracked it down to the Mag. Took the mag off check the point and condenser and those looked fine....swapped the coil with another new one that I had on hand.......nice blue spark :D ...Re-installed and timed the mag.......tried to start it with the starter....turned over ....didn't even hit once.....released the starter and BAM!! the flapper on my muffler almost went into orbit!!! Flames about 2 ft high out of the muffler. Re-checked timing.....right on.....checked again....timing is correct...... What am I missing?

I am going to pull the valve cover when I get home today......I am worried that somehow the cam isn't turning somehow and the valves are staying open......scary!! :shock: ...just in time for Halloween I guess........ :?

Appreciate any help or suggestions.

Re: Back Fire!!

Mon Oct 29, 2012 8:29 am

Are you sure you aren't 180 degrees off time? If the mag was set with the #1 piston on top during exhaust instead of compression you could get what you are getting.

Re: Back Fire!!

Mon Oct 29, 2012 8:32 am

My first guess is that you've timed it 180 deg. off. Second guess is plug wires in wrong sequence. Is the rotor properly timed to the pinion gear?

Barnyard's too fast for me!

Re: Back Fire!!

Mon Oct 29, 2012 8:33 am

Barnyard wrote:Are you sure you aren't 180 degrees off time? If the mag was set with the #1 piston on top during exhaust instead of compression you could get what you are getting.


I agree with Barnyard, backfiring is usually a timing issue. Ed

Re: Back Fire!!

Mon Oct 29, 2012 8:47 am

I have timed it several times before and am pretty sure It was on the compression stroke (Turned it over with #1 plug out...finger over hole....felt pressure .....turned to mark ....then rotated mag till it clicked).....I will check it one more time. I removed the rotor assembly but the shaft is keyed so that should have been fine as I didn't remove the rotor itself. The tractor was running perfectly .....only removed #1 wire to remove plug.....I am certain the wires are correct.

Thanks for all the suggestions....

Re: Back Fire!!

Mon Oct 29, 2012 8:57 am

CPIII wrote:Re-checked timing.....right on.....checked again....timing is correct...... What am I missing?
The tractor was running perfectly
Ignition timing fault some place, as the guys suggest.

Re: Back Fire!!

Mon Oct 29, 2012 9:09 am

I corrected the issue with the "no spark" which initially caused the tractor to not start.........I will re-check everything again tonight and maybe take some video so hopefully someone can spot my mistake.....

Thanks again guys!

Re: Back Fire!!

Mon Oct 29, 2012 9:15 am

CPIII wrote:I removed the rotor assembly but the shaft is keyed so that should have been fine as I didn't remove the rotor itself.

If you put this back without making sure the rotor ended up pointing back the same direction, you had a 50/50 chance of getting it right. The pinion gear on the shaft turns 2 revolutons for each turn of the rotor. Take this back off, turn the rotor 1/2 turn and put it back. Probably all you need to do.

Re: Back Fire!!

Mon Oct 29, 2012 9:28 am

Wow...didn't realize that......guess i have been getting lucky all the other times I have had it off......Thanks Jim!!

Re: Back Fire!!

Mon Oct 29, 2012 9:33 am

Re run your finger over the hole TDC line up on plug one then pop off the cap to verify the rotor is pointed to the distributor cap tower that #1 plug wire is connected to.

Re: Back Fire!!

Mon Oct 29, 2012 9:52 am

Jim Becker wrote:
CPIII wrote:I removed the rotor assembly but the shaft is keyed so that should have been fine as I didn't remove the rotor itself.

If you put this back without making sure the rotor ended up pointing back the same direction, you had a 50/50 chance of getting it right. The pinion gear on the shaft turns 2 revolutons for each turn of the rotor. Take this back off, turn the rotor 1/2 turn and put it back. Probably all you need to do.

That is what is called 180 degrees out of time.

Re: Back Fire!!

Mon Oct 29, 2012 9:57 am

Cub tip of the week - "An Alternative Take on Finding TDC When Timing A Cub"
http://farmallcub.com/phpBB2/viewtopic.php?f=1&t=17676&p=482422#p482422

Re: Back Fire!!

Mon Oct 29, 2012 10:46 am

I have had the rotor cover off tons of times .....guess i got lucky each previous time going back together.... :oops:

So hopefully when I get back home a can change my tractor back to being a tractor instead of a shotgun 8) ......Neighbors thought I was bird hunting in my back yard :lol:

Re: Back Fire!!

Mon Oct 29, 2012 11:30 am

Winfield Dave wrote:Cub tip of the week - "An Alternative Take on Finding TDC When Timing A Cub"
http://farmallcub.com/phpBB2/viewtopic.php?f=1&t=17676&p=482422#p482422


Good method if the valve cover had already been removed but I wouldn't recommend removing it to to locate TDC.

Re: Back Fire!!

Mon Oct 29, 2012 2:12 pm

lazyuniondriver wrote:
Winfield Dave wrote:Cub tip of the week - "An Alternative Take on Finding TDC When Timing A Cub"
http://farmallcub.com/phpBB2/viewtopic.php?f=1&t=17676&p=482422#p482422
Good method if the valve cover had already been removed but I wouldn't recommend removing it to to locate TDC.
I [and others] would recommend it...2 bolts and you know for sure TDC.