Buddy's Late 8N - Won't Start

Thanks to all you guys' help here, and from working on my own 841 getting her running this spring, I felt like had just enough knowledge (which may be a dangerous thing) to help a friend of mine get his late 8N started (side-mounted distributor). We pulled it out of the barn, rolled it down to his work shed, flushed the radiator (didn't have a cap--let him have my old one for now), turned the motor gently by rolling it in 4th gear (per advice gotten here), drained out the old gas, hooked up jumper cables (it's a 12V conversion)...no spark.

No way to easily diagnose, so I went to the most likely issue and he spent ~$10 for new points and a condenser. The plugs looked awful, so he got new plugs, as well. Did the best we could gapping the points, got yellow spark. No start. We tinkered with the points a while, still the best we could get was a weak yellow spark.

I know you "don't throw parts at a problem," but I'm wondering if it could be the plug wires, since we're getting some spark, just not a bright blue one. They don't look in the best shape. Or could we still have the points gapped wrong? I used a dollar bill as I've seen my uncle do.

Isn't a coil either "all or nothing"? Or could it cause a weak spark, as well? Didn't see the brand, but it's a 12V, no resistor needed type.

Also, as a separate issue, we can't get the rotor cap off the post. On my 841, there's a clip you slide and the cap comes right off. His cap looks identical to mine, but I can't find the clip, and it won't budge. Made gapping the points an interesting process...
 
but I'm wondering if it could be the plug wires


Pull the coil wire out the dist cap and check the spark there.
If it is good there and you have a new dist cap and rotor then yes the plug wires are bad.

If the spark is weak at coil wire you have problems before that point.
Points; condenser; coil; power to points.
 
(quoted from post at 22:41:19 09/15/14) I don't think a dollar bill is enough gap for the points, ok to wipe points clean but not to gap.
orrect! If he has them gapped at dollar bill thickness (~0.003?), that is far too close & will result in weak spark (all the energy is going into the arc at points, not to HV for plugs). Set to0.025"
 
(quoted from post at 09:37:49 09/16/14) Thanks, JMOR! So something like the thickness of the box the points came in?

0.025" is correct. Just for reference, a business card is typically about 0.015". So, a "little less" than two business cards...

Or get a feeler gauge set and get it spot-on.
 
"we can't get the rotor cap off the post. On my
841, there's a clip you slide and the cap comes
right off"

Look carefully. There should be a clip. Or someone
has goobered it up.
 
(quoted from post at 00:38:37 09/16/14) Thanks to all you guys' help here, and from working on my own 841 getting her running this spring, I felt like had just enough knowledge (which may be a dangerous thing) to help a friend of mine get his late 8N started (side-mounted distributor). We pulled it out of the barn, rolled it down to his work shed, flushed the radiator (didn't have a cap--let him have my old one for now), turned the motor gently by rolling it in 4th gear (per advice gotten here), drained out the old gas, hooked up jumper cables (it's a 12V conversion)...no spark.

No way to easily diagnose, so I went to the most likely issue and he spent ~$10 for new points and a condenser. The plugs looked awful, so he got new plugs, as well. Did the best we could gapping the points, got yellow spark. No start. We tinkered with the points a while, still the best we could get was a weak yellow spark.

I know you "don't throw parts at a problem," but I'm wondering if it could be the plug wires, since we're getting some spark, just not a bright blue one. They don't look in the best shape. Or could we still have the points gapped wrong? I used a dollar bill as I've seen my uncle do.

Isn't a coil either "all or nothing"? Or could it cause a weak spark, as well? Didn't see the brand, but it's a 12V, no resistor needed type.

Also, as a separate issue, we can't get the rotor cap off the post. On my 841, there's a clip you slide and the cap comes right off. His cap looks identical to mine, but I can't find the clip, and it won't budge. Made gapping the points an interesting process...

I would START with wires. Poor spark is often because the DPO (Dreaded Previous Owner) installed resistor wires with modern cores. Old machines require copper core wires, nothing less. And this will maybe surprise you - install new battery cables. I got this advice many years ago and didn't believe it until I happened to change the cables on a Cub Cadet I have. You'd have thought I got a new engine. It smoothed out, runs with more power, starts effortlessly, etc. Really a surprise.

Apparently, the corrosion inside the cables interferes with the strength of the current to the coil. The coil cannot overcome a weak signal from the battery, nor can you ever get a good spark with a weak ground. Cables are cheap, too.
 
(quoted from post at 05:37:49 09/16/14) Thanks, JMOR! So something like the thickness of the box the points came in?

You have a new spark plug laying there.
Find something that matches its gap, then stick it between the points.
In the field, I just eyeball em. If the point gap looks the same as a new plug gap(side distributor),
it'll run........excepting other issues of course.

disclaimer..if it's a new plug from the land of never right...all bets are off :D
 

In the old days we used a match book cover as an emergency gauge for setting points. Dont know if it was correct as I never measured it.

But..

are you choking the carb fully while cranking,, its an updraft and must have a really good working choke when cold to allow it to pull the very heavy gas mixture UPWARDS... If you cant make the plugs wet, then your not choking it enough.
 
We did some more work yesterday afternoon. Still can't get anything beyond a yellow spark (although at one attempt it looked to have a little blue in it). I am just wondering if we're getting the points wide enough, since it was mentioned that the points need to be gapped as much as the plugs.

Still can't get the rotor cap off. I'm starting to think someone "boogered" it up.

I think our next step will be taking the battery cables off and making sure they've got good ground, cleaning the terminals good, and checking that the choke is choking correctly.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top