Backfiring

[Gator73]

I just put in a new distributor for my 8n and made sure it was
all times up n when I hit the starter switch it started to backfire.
Any suggestions?
Thanks
Gator

 

[Bruce (VA)]

front or side distributor?

6v or 12v?
75 Tips

 

[Gator73]

12volt
Side mount distributor

 

[Bruce (VA)]

start w/ the easy stuff first.

Confirm the correct firing order, 1-2-4-3, ccw.

If that does not fix it, start over.

Remove the #1 spark plug. (removing all of them makes the job a bit easier) Ignition off, place your thumb over the #1 spark plug hole and crank slowly until compression is felt. Continue to crank the engine until you see the timing mark, 0* (top dead center) on the flywheel through the timing hole in the right side of the bell housing. Use chalk on the flywheel to exactly align the 4 degree mark with the pointer. Hold the distributor beside the engine. W/ the distributor oiler at the 7 o'clock position & the stud at 9 o'clock, turn the rotor until it points roughly at the right front head bolt. (close counts) Now insert the distributor. Rotate the distributor housing counter clockwise until the points are closed. Put the cap on & double check the plug wires, 1-2-4-3, CCW. Then, remove the primary wire from the side of the distributor (or at the coil, whichever is easier) Put one lead of your VOM (set on resistance) on the stud on the side of the distributor & the other on the block or other good ground. Slowly turn the distributor. The needle will move as the points close & then open. Find the exact spot just as the points open & then tighten down the distributor.

Now check your work (and the dynamic timing) w/ a light.

If it won't idle below 500 rpm (400 is better) don't bother w/ a light.

If it idles ok, make 3 marks w/ chalk or white paint on the flywheel:

4*
10*
17*

Start the engine.

At idle, the light should flash & the marker should line up exactly at 4* if you did the static timing correctly.

If not, loosen the distributor & turn it until the marks line up. It should take very little adjustment.

Once you've got that done, increase the engine speed to 1200 rpms. The light should flash & the marker should line up w/ the 10* mark. Then, increase the rpms to 2000 & look for the marker to align w/ the 17* mark.

Close counts on the advanced timing. A degree or 2 either way is ok. But, no movement or 5* or more off means you have an advance weight problem. You don't adjust the distributor to fix that.
75 Tips

 

[Gator73]

Thanks a lot!
Gator

 

[Bruce (VA)]

You're welcome.

Got it running?
75 Tips

 

[Gator73]

Not yet still trying.
When I get #1 on compression stroke and I go back to the flywheel I don't see any numbers on the flywheel is that normal or 180 off?
Gator

 

[R Geiger]

(quoted from post at 08:19:37 09/15/17) Not yet still trying.
When I get #1 on compression stroke and I go back to the flywheel I don't see any numbers on the flywheel is that normal or 180 off?
Gator

no, not normal, make sure you are on compression stroke at top dead center. that is when the timing marks should be there. can be hard to see at times. I light to put some white paint on the ones i use.
there are two sets of marks on the flywheel. 180 degrees apart.
good luck

 

[Bruce (VA)]

No, it's not 180 out if it's on the compression stroke. Those numbers are just hard to see. Get a BF screwdriver and move the flywheel a tooth or two st a time. Use a flashlight. Marks are there.

 

[Gator73]

Well,she is trying to crank but I haven't got her there just yet.
Any suggestions?
I thought maybe take the distributor out an turn it clockwise one tooth and see what she does.
Gator

 

[Bruce (VA)]

(quoted from post at 13:11:34 09/20/17) Well,she is trying to crank but I haven't got her there just yet.
Any suggestions?
I thought maybe take the distributor out an turn it clockwise one tooth and see what she does.
Gator

Did you find the compression stroke, timing marks & insert the distributor as I suggested above? And set it w/ a meter?

 

[Gator73]

Yes Sir,She's trying to crank up but not there yet.
Any suggestions?

 

[Bruce (VA)]

(quoted from post at 04:37:54 09/21/17) Yes Sir,She's trying to crank up but not there yet.
Any suggestions?

If you put the distributor back in & set the static timing exactly as I described, then timing isn't your problem.

You need to answer 2 questions before you do anything else:

With the bolt in the carb bowl removed and the gas on, will the fuel flow fill a pint jar in less than 2 minutes?

Next, get out your adjustable gap spark checker * , open the gap to 1/4", hook it up, turn the key on and crank the engine. Does the spark jump 1/4"? Post back with the answers.

And do not buy a new part for the tractor until you can answer this question: how do I know the part on the tractor is defective?



* Don't own an adjustable gap spark checker? Buy one! Not a test light! Until then, take an old plug, open the gap 1/4" ground it to the head & look for spark. It’s not the color of the spark that counts; it’s the distance it jumps.