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A buddy called me last night and wants me to take a look at his sled, it's a late 80's early 90's 500 or so Arctic Cat, he just got it last year and doesn't know a lot about it other than it ran good until the end of the season. It was rebuilt before he bought it and towards the end of the season he said when you started it, it would run for a few minutes and then just shut off like someone hit the kill switch.

He figures it's electrical but isn't sure where to start looking. Stator? CDI? Not that familiar with Cat's but I'm sure they are like any other 2 cycle engine.

Anyone have this experience?
 

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Cats have a lot of issues with safety switches in the throttle or carbs going bad. There's also a couple of plastic bushings on the throttle lever pin that break, which can cause problems. Also, check the tether if so equipped. Sometimes the tether doesn't push in on the switch completely and the engine will die.

You can disable the carb safety switches by jumpering, I think Blaine1 has posted a video of how to do that. I would check all those first, even if it's just to rule out problems before heading to the stator/coils.
 

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Closed Ignition: Primarily Pre-1998
A "Closed" ignition means the wiring needs to have a closed circuit in order to run. If the connection to any switch; key, kill, tether, throttle safety switch, etc.. is interrupted there will no longer be power to the ignition system and spark will cease. All Cats 1997 and earlier run a closed ignition, with the exception of the 1997 ZR 580 that is an open ignition.
Diagnosing no spark, weak spark or intermittent spark issues
First you want to see if it an issue in the switches/handlebars or if it is in the primary ignition components: stator, cdi, coils, trigger coil or possibly plugs, plug wires or plug caps.
1. First put the spark plugs in the spark plug boots and lay them on a cylinder head bolt so they are grounded. Make sure the plugs are not near the spark plug holes when you pull it over.
2. Pull the recoil rope checking the spark at the plug. Is there spark at each spark plug? Is the spark blue (indicating a strong spark) or is it yellow/orange (indicating a “weak” spark). If you have nice blue spark on one plug (if it is a twin) or two plugs (if it is a triple) and not the others, it may be as simple as having a bad/fouled out plug. Try replacing the non-sparking spark plug/plugs with new a new plug.
3. The next step is pretty much the same if you had no spark or a weak spark. On the “Closed” ignition you unplug the connector from the stator containing the yellow wires. This connector sends the power to the lights, hand warmers and tachometer. When you unplug this connector you need to put a jumper wire connecting the 2 “non yellow” wires together in the connector. This completes the electrical circuit which is needed to check for spark. I have a youtube video showing how to do this. By putting this jumper wire between the 2 non yellow wires you are bypassing all of your switches (Throttle Safety Switch, Kill, tether ect..) all of your lights and hand warmers ect..in your handlebars. Pull the recoil over and see if you have spark or if the previous yellow/orange weak spark is now blue. Carbureted models can be started and run with this 4-prong connector unplugged and the jumper wire in it but you won’t have lights ect..as mentioned before. If you have an EFI, you can only check for spark and it will not start or run with it unplugged. You need it plugged in to power your fuel pump. You can hook up a battery to the fuel pump and start it.
4. If by using the jumper wire you now have spark, there is something shorted out in your switches like the tether, throttle safety switch or kill switch. If you had weak spark and now have blue spark it also tells you that you have a short with one of your switches. Again likely culprits are the TSS, tether or kill switch. There is a 3 prong connector in your handlebars that if you unplug and jump the 2 outside prongs it will bypass your kill and TSS switch. After bypassing these switches you will only be able to start and turn off your sled with the key. I have a video on youtube showing how to do this. The 3 prong connector is usually not by the thumb throttle but rather just a little bit down the steering shaft about at the point where the console containing the key switch is located. If you’re not sure which connector it is, just follow the group of wires from right handlebar area down to where the plug is located. There are a few other plugs by the handlebar on the right side by the thumb throttle, but they contain yellow wires and are for your hand warmers and thumb warmer. You also need to bypass the tether. You can just cut the wires in the back of the tether and splice the wires together which "completes" the circuit.
5. If after unplugging the 4-plug switch and using the jumper wire you still do not have spark or the spark continues to look weak this tells you that the problem is in the major ignition components like the stator, coils, cdi, spark plugs, spark plug wires or trigger coil.
6. The first thing to check is the connection from the stator to the cdi. Make sure all connections are free of moisture, are tight and use a little bit of dielectric grease on it. Check the ground. You should have a ground wire coming from your stator and your CDI/ECU box. Make sure the grounds are clean, tight and that the ground wires are not broken. Sometimes the ground wire is pinched and broken inside the eyelet connection and is making only intermittent if any connection. Some older model Arctic Cats have the ground up closer to the handle bars on what some would consider the “firewall” of the sled and they are notorious for rusting/corroding out badly.
7. If all connections are solid and the ground checks good then you start electrically checking components. Most twin triggers are 90 ohms and most triples are 175 ohms. I have a video on youtube showing how ot check it. It is very easy and quick to test. The frustrating part about the trigger coil is that it can test good, but still be bad.
8. Next you want to test the stator itself. I have several videos for different models on youtube. I have 3 separate tests using the 3 main plugs used on carb and EFI 1990’s model stators.
9. If you continue to have no spark/weak spark and your trigger tests ok then we may be looking at a secondary coil issue. First you want to make sure the spark plug caps are on tight. They just screw on and off the spark plug wire. If your wires are long enough unscrew the spark plug caps, trim a ½ inch off the end of the wire and then screw the spark plug cap back on. Also, some spark plug wires unscrew from the coil itself. I had 2 sets of coils go “bad” on my sled. My triple coils showed 1 spark plug with extraordinary blue spark and the other 2 plugs were weak/yellow-ish in color. After I trimmed them and screwed them back together they ran perfect. Warn spark plug ends usually cause a miss or acts like a rev limiter. Be warned though that I did have one wire that would not unscrew from a coil and I ended up tearing the spark plug wire. Also, always check the spark plug gap and set it to the correct specifications.
10. If you have no spark and your trigger tests ok, your stator tests ok and you have trimmed the plug wires then we’re looking at a possible bad CDI box There is no real good way to test the CDI other than swapping the box out with a known good CDI box.
11. Specificly on Battery EFI sleds here is another thing to check. There can be a bad relay on the back of the ecu. There are 2 of them back there 1 for the spark and 1 for the fuel pump.
12. Also, bad reeds on a sled will cause it to back fire and run poorly acting like it is an electrical issue.
13.Other issues that I have seen/read that have caused a no spark/bad running issue:
A. Wrong flywheel on it.
B. Frayed wires in the wiring harness or under the seat caused a short
C. Sled was only running on one cylinder. Low side coil on his stator read 360 ohms and it should have measured 450 ohms. The low side coil was bad.
D. It kept fouling plugs left and right. The guy before me ran ethanol, and never told me. This was on an EFI sled.
E. Hood harness was routed between rewind/stator housing and frame and had 4 wires smashed. Repaired wires and ran good.
F. Got it running again tapped the ECU and died. Pulled the ECU cover off and found some corrosion
G. Wires running to the carbs were rubbing against the jack shaft (Shaft going from secondary clutch to the top sprocket in the chain case). After rewrapping/rerouting the wires it ran great
H. Bolt for the recoil cup broke off and hit the trigger coil, bent the bracket slightly and gave it too much air gap. Air gap between the trigger coil and flywheel should be around .010-.020. I know it will not fire if the gap is .040.
I. Oil Injection turned up too high
J. Fuel Lines hooked up backwards
K. Lean jetting will cause a bog. The sled would start and idle but if you pinned the throttle the sled would bog and quit running. We were able to determine that it ran better when you choked it a little. We jetted up and it ran good.
L. Sheared Timing key
M. Crank out of Phase will cause it to run very poorly.
N. Too much dielectric grease in the trigger connector caused sled to bog.
O. Bad TPS Switch/TPS wires shorting/grounded
P. The wire on the carburetor was put on backwards
Q. Loose key switch wire
R. Harness got to close to the pipe and fused wires together causing no spark issue
 
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