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Discussion Starter · #1 ·
Just picked up an 86 fourtrax 350 4x4. It's been sitting for a while. Previous owner told me it ran when he parked it, but it was backfiring and thinks the valves just need adjusted.

So, I've put new battery, new oil and filter, new spark plug.

When I hold the plug to the head, I get spark. It's not a bright spark like a car would get, but there is a spark I can see. Should it be a bright spark? Also what should the gap be? It's at .025

Next is fuel delivery, I'm getting fuel to the carb b/c when I take the plug out of the bottom of the bowl, gas comes out. But I'm not sure if it's making it into the motor. Is there a way I can tell? I was trying to start it with the airbox and filter off and I could see a couple drops of gas shoot out of the carb.


Will it crank in any gear but neutral?

Can I use automotive gear oil for the differentials?

I've got it cranking, but won't start. So, that's why I'm wondering if I've got enough spark and the gap.

Thanks for the help. I'm sure I'll have more as I get deeper into this thing.
 

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have you tried spraying starting fluid into the air intake? If it will run until the starting fluid burns up, then you know it has enough spark, and the problem will be in the carb (assuming you have already drained the old fuel fromthe tank and replaced with new.) Anything that has been sitting for a while needs a carb job, so I would go ahead and get that out of the way first. Then if you can get it to run, burn a few tanks of fuel with Seafoam in it (see post in this section) before you do anything else.
 

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Discussion Starter · #3 ·
I've sprayed starting fluid into the carb/motor, but the fluid is probably a little over a year old. So, I'm going to pick up a new can tomorrow and try. Will be ordering a carb rebuild kit off ebay tonight. Thanks.
 

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You can also just take the sparkplug out and pour a little gas down into the cylinder. Put the sparkplug back in and see if it will start and run for a second or two. If not, then the carb is probably stopped up.

You should have a bright blue spark.

You can use automotive gear oil in the differentials.

It needs to be in neutral before it will start.
 

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Discussion Starter · #6 ·
Couple more questions.

If I have fuel and spark, is there anything else electrically that could prevent it from starting?

None of the lights light up on my "dash" and the fan isn't plugged in, could that prevent it from starting too?
 

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Couple more questions.

If I have fuel and spark, is there anything else electrically that could prevent it from starting?

None of the lights light up on my "dash" and the fan isn't plugged in, could that prevent it from starting too?
I would try to get power to the lights and get them working like they're supposed to, because that bike has the electric fuel pump and control unit. Usually, the neutral light needs to be on, but since you already have spark and fuel, the electrical shouldn't keep it from starting, but it might keep the electric start from working. The neutral light bulb is probably blown or the bulb and socket might be corroded. Don't hold me to that though, because it's been a long time since I worked on one of those Fourtrax 350s. Those Fourtrax 350s are wired up different and have a lot more wiring than most of those older ATVs. It's a little more complicated.
 

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If the pump is working you'll hear it when you turn on the key. It's on the right side of the machine, under that panel. It should pump a few times until it builds up pressure. Once there is pressure it may cut off, but it at least should pump when first turned on after sitting for a while.

If you don't hear that, then it has no fuel pressure.
 

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Discussion Starter · #9 ·
So, I have fuel and have adequate spark. I tested with a different coil off a running bike. Would the valves needing adjusted keep it from starting? That's next on my list of fixes. Have to adjust the valves and replace the choke cable b/c it's frozen.
 

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I would try pouring a little gas down into the sparkplug hole and then quickly put the sparkplug back in before the fuel evaporates and see if it will start and run for a second or two.
 

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Discussion Starter · #11 ·
Tried that with starting fluid. Nothing. I haven't tried starting it with the kick start though. I should probably try that tomorrow. Maybe the elec start isn't cranking fast enough.
 

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If it doesn't start by putting gas or starting fluid down the sparkplug hole, then I would check the compression with a compression gauge. I would try adjusting the valve clearance, first, though.
 
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