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Discussion Starter · #1 ·
I'm getting so frustrated. I have 2 jag 340s. Both 78s. Bought recently. One was easily back to running condition with a clean out fuel tank and a dang ignition switch. The other was ran on straight gas and nearly seized. Here is my issue...

Motor was just completely rebuilt, ignition switch and throttle safety switch just replaced. They test "open" when "on" as per the manual. Everything thing else checks out other than the inability to test CDI, but precious owner put a new one on. It will run however when you unplug the engine wire harness. Although you have to jump the "non-yellow" wires! Which confuses me because my other 78 jag will run with the engine harness unplugged also but not with a jumper! Maybe someone swapped in a 79 spirit engine (I think they switched from NO to NC some years after 78?) What am I missing??? I was thinking maybe a ground wire could on the sled side harness is bad somewhere...urgh electrical. Let me know what you guys think. First time posting. Love the forum btw. Y'all have helped me so much already
 

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Did you clean the carburetors? If not then do so on both. Along with changing out the fuel filters, cut back a 1/4" off the spark plug wires and replace the caps as well. Along with replacing the fuel pumps because if they are that old then I would do them regardless for the cost so you know they are good along with changing out all the fuel lines, make sure the gas tank has the weighted fuel filter on the end of it as well.

As far as electrical others are better at that then I am.
 

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Discussion Starter · #3 ·
Did you clean the carburetors? If not then do so on both. Along with changing out the fuel filters, cut back a 1/4" off the spark plug wires and replace the caps as well. Along with replacing the fuel pumps because if they are that old then I would do them regardless for the cost so you know they are good along with changing out all the fuel lines, make sure the gas tank has the weighted fuel filter on the end of it as well.

As far as electrical others are better at that then I am.

Literally all new! Rebuilt pump, new filter, new lines, cleaned tank (weight did fall off but on now). Single carb...totally clean like new. Didn't cut back the plug wires but they ohm tested perfectly. It runs and idles perfectly but just when jumped on unplugged engine harness. Even tried leaving it plugged in and alligatored clipped the ground wire to give it artificial ground to frame. It had to be sled side wiring issue but I just can't figure out what. Does anyone know where ground wire actually attaches to the frame? I guess it's grounded to the motor from the sparkalator....maybe I run a ground wire from frame to motor??? Or just not buy a 40 year machine...
 

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Wait for KCCats to arrive he is the Arctic Cat guru around here. You covered what I would do so idk, I replace caps every few years as they get brittle and loose and for the cost of 3 bucks a cap eh I just replace. I've had one go bad on me out on the trail many years ago and since then I do that and keep spares with me at all times. I would just make sure the in gas tank line is Tygon as that is the only stuff you can use other then that wait for KC and good luck!
 

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Discussion Starter · #6 ·
KC should be able to answer. My "guess" is that the engine in it is a short to ground type for shutting off and the switches etc are set for a "open" circuit type for shutting off. Hence why when it's plugged in it doesn't run.

I think your right! Engine is a AA34F4, which may be a '79. The '78 manual calls for engine AA34F3. I'm still confused though, because I thought a '79 should still be normally open to run also??? Pulled the plugs and messed with the safety switches. I do get spark with TSS in off position and key switch in off or on position. This makes sense to me if the engine is in fact "NC" to run and my switches are "NO" but I'm not convinced the AA34F4 is "NC" to run...Could a bad ground going to the CDI box cause this "backwards" operation? It works with a jumper, which is basically just grounding the CDI. Also, previous owner installed this CDI BOX...Do CDIs come open or closed? I removed the CDI to look for part number and noticed some melting on engine side of the box. Very slight. Maybe I'll swap the cdi from my other sled and do continuity test on switches again to rule out cdi.
 

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Welcome
OK ok what I have learned is that although they say it is an open system not all from that era are! Dont get hung up on it!
Again New dont mean anything any more double check it!
There would be a ground inside the flywheel! (Brown)
But there should be a jumper wire from the upper recoil bolt to the chassis
Check the wire color chart above in this section
 

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"Jumped" typically means a NC system. Key ignition can be just re-wired, but if you have a kill switch or tether, they will need to be the correct type. I have a 1989 and 1990 that is a NC system and a 1999 that is NO.
 

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They were all normally open til 94 but I have found several that were in the Norm closed
 

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Discussion Starter · #10 ·
Yeah I'm coming to that realization...the key switch is a simple swap, but I'm having trouble finding a TSS switch that even mentions whether it's "NC" or "NO" on description. May have to just disconnect it and run some kind of a tether switch instead...
 
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