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Discussion Starter · #1 · (Edited)
I just picked up a Mule model 2520 kAF620B
It has good spark and I cleaned and rebuilt the carb. It will not start, it backfires, as if the timing is off. I replaced the ignition module and no change. I tested the pickup coil resistance and they both were 115. Compression is 190 and 195psi. The timing marks on the flywheel line up with top dead center, but the flywheel magnet is not near either pickup coil? Doesn’t the magnet trigger the spark when it passes the pickup coil? See picture
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How can it trigger the coils if the magnet is in the middle. Should be firing #2 cylinder based on timing marks? How is spark triggered if not by magnet??
 

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"Doesn’t the magnet trigger the spark when it passes the pickup coil?"

I think the pickup coil is the magnet, and it's triggered by the protrusion on the rotor passing by the magnet.
If you have spark but suspect a timing problem, suggest hook up a timing light, check it.

Otherwise, sounds like it's back to the carburetor, to get the idle passageway, slow jet, choke system cleared out?
 

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Any chance the ignition wires got swapped somewhere in the path?
Not looking at your manual, but in general, the magnet will be well past the pickup when the flywheel mark gets to TDC, so the timing can be andvanced.
 

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Discussion Starter · #4 ·
Any chance the ignition wires got swapped somewhere in the path?
Not looking at your manual, but in general, the magnet will be well past the pickup when the flywheel mark gets to TDC, so the timing can be andvanced.
The wires from the pickup coils, ignition wires and coil all look like they have never been moved. They lead into a wire harness that only plugs in one way. I can’t figure out how you change the timing. It looks set with no way to adjust. The pickup coils don’t move other than in and out. Flywheel has a key, no movement. Ignition module can’t adjust. Manual says timing is static and does not advance. How can it be off???
 

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If the ignition timing is off (and that remains to be confirmed) it could be because the flywheel key has sheared. I think it unlikely but you asked the question.

Also, I think your timing is advanced first by the position of the pickup coils relative to the flywheel protrusion and secondly by an electronic advancer in your igniter. Note I don't have a service manual for your Mule but I do know that some Kawi igniters provide electronic advance which does away with the spring loaded mechanical advancers.

I assume you are getting a healthy spark at both spark plugs?

Have you checked your valve clearance and valve timing? I would at least check those before taking the carb apart again.
 

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Discussion Starter · #6 ·
I pulled flywheel and key is intact. So for fun, I rotated the crank on the flywheel without the key to where the flywheel protrusion (magnet) was just before the pickup for cylinder #1. Tightened flywheel and it started and ran on only cylinder #1! It ran fine and idled only on cylinder #1. Pulled flywheel and aligned for #2 pickup, tightened and got it to run on only #2!
How can that be!!
BTW, I adjusted valves earlier.
 

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Discussion Starter · #11 ·
Both plugs fire at the same time on compression and exaust ... Check spark plugs .....
Wouldn’t they have the same Top Dead center if firing at the same time, just one on compression and one on exhaust? TDC are different on each cylinder based on my check placing slick down spark plug here Le and per the service manual. Why would it run on only one cylinder moving the flywheel (without the key) to line up with timing mark? I can do this with each cylinder and get it to run on that cylinder, so it is not the valve timing or spark plug.
Find the service manual at Manualslib.com ...PDF version .....
I have it, shows timing as static, no advance.
 

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Also, I think your timing is advanced first by the position of the pickup coils relative to the flywheel protrusion and secondly by an electronic advancer in your igniter. Note I don't have a service manual for your Mule but I do know that some Kawi igniters provide electronic advance which does away with the spring loaded mechanical advancers.
That's what I thought too, and that's how most motorcycle engines and some ATV engines work.
This particular model is more like a generator engine, using a Governor system of rods
and springs to change the amount of fuel needed to support the rpm's called for.
 

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Back to Basics?

"I just picked up a Mule model 2520 kAF620B"

Did previous owner provide any background, anything beyond "ran fine when I put it away two years ago"?
Why did you dial into ignition right away, instead of intake/ carburetion?
 

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Back to Basics?

"I just picked up a Mule model 2520 kAF620B"

Did previous owner provide any background, anything beyond "ran fine when I put it away two years ago"?
Why did you dial into ignition right away, instead of intake/ carburetion?

AND

Who put the red marks on the flywheel and pickups, and why?
 

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Discussion Starter · #19 ·
Back to Basics?

"I just picked up a Mule model 2520 kAF620B"

Did previous owner provide any background, anything beyond "ran fine when I put it away two years ago"?
Why did you dial into ignition right away, instead of intake/ carburetion?

AND

Who put the red marks on the flywheel and pickups, and why?
Mule had been sitting on a farm for a couple years, no history.
First thing I did was pull the carpet and go through it and clean all the passages and rebuild it. It had spark and good compression. That’s when I tried to start it and it would backfire would not start. As I mentioned earlier, when I change the timing to those red marks, It will start but only run on #2. Runs fine and idles, but only on #2. I can move flywheel and get it to run in #1, so not carb or valves. It just will not run in both cylinders when I put the flywheel where it should be with the key in it. Very confusing!
 
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