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'03 400 backfiring/bogging under throttle

47K views 6 replies 7 participants last post by  DUHNIS 
#1 ·
Hi fellow AC riders! First time poster here! I'm sorry that my first post is a request for help. Here's the scoop:

My riding buddies and I went to the "Sunday at the Park" event at Carolina Adventure World on 4/01. It's was a great ride. Man it was packed! Anyway, we rode throughout the morning and part of the afternoon with no issues. My 400 was running great. Out of the blue, she backfired on me and I lost power. I pulled over and poped it into neutral. She wouldn't rev with the throttle. The engine would only sputter and bog down, kinda like the choke was hung. I cut it off and started checking a few things. The oil level was perfect. The choke cable seemed to engage/disengage just fine. The air filter was a little dusty, but it didn't appear to be enough to hinder the air flow. I went ahead and drained a little fuel from the carburetor float bowl in case condensation had built up. I didn't remember the fan running, so I checked the fan fuse, but it was good. I didn't remember noticing the temp light coming on either. After not finding any obvious problems, I cranked her back up and she ran fine and rev'd fine with the throttle. I rode it up and down the trail a couple of times with no trouble. The guys said it was probably just a fluke, so we took off again. After another 10 minutes, the same thing happened - backfire, then loss of power. I pulled over and cut it off again. We tossed around some ideas among us, but we couldn't find a clear cause for the symptom. None of us had tools other than our standard atv kit. I cranked it up after sitting for 10 minutes or so, and it ran fine, so I took off for the parking area. She died once more on the way back, so I opted to let my buddies tow me. On the drive home I began to think it she could be overheating. I don't remember the temp light ever coming on, or the fan running. Could the cooling fan switch be bad? Would it prevent the fan from running and the temp light from coming on too? Or do you think it could be something else? I'd just take her to my local dealer, but they are 2 weeks plus behind with the riding season coming into full swing right now. Plus, my riding buddies just invited me on a trip to WV in a couple of weeks. I hope to get her back in shape in time to make the big ride. I thought somebody on ArcticChat may know exactly what's going on.

Thanks in advance for your help!
Woodbutcher
 
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#2 ·
Sounds like a bad coil. Had almost the same thing happen last year with an old 500 Bearcat. When it was cold, it would run fine, but once the coil warmed up, it would short some of the windings and cause a misfire, so bad that it would kill the bike. Once it sat for a while, it would fire up and run good for a little while until the same thing happened again. Eventually he got towed out as the coil gave up. I would check that first, look for any cracking of the outer case or carbon tracks to the frame. If it's running fine when it's cold, I wouldn't suspect a fuel problem.
 
#3 ·
Welcome aboard Wordbutcher.

Sounds like the ubiquitous fuel delivery problem. Could be water or dirt in the fuel. Just because you drained the float bowl doesn't mean you've gotten all of the contamination out of the fuel. Drain the float bowl into a clear container and look for contamination. Shake the machine around to slosh the fuel. Pull the fuel line off of the carb and run a cup full or so of fuel out of the tank. Look for more contamination. Pull the float bowl off of the carb and look for contamination. If you find water or dirt in the fuel, I'd drain the fuel tank completely into a gas can using a siphon that can reach the bottom of the tank. You want to suck up as much contamination off of the bottom of the tank as can be reached. What I use for this purpose is piece of hose attached to a small diameter plastic pipe. The pipe works like a vacuum cleaner wand and you can get it into more places in the tank. When that's done, put in fresh clean gas, put an in-line fuel filter on and see how it goes. Good luck.
 
#4 ·
hello all i'm new here and was reading your problem i had a similar problem, i have an 03 ac 500 auto, running fine up and down the lane, then took it out in some snow, and soon as it was under good load it would bog and bog then stall, would not restart for about ten minutes, took it back to garage and checked all fuel supply, found that when i changed my bars the vent tube for gas tank was kinked, staightened it out and made sure it was clear and bam problem solved, so in any event it does sound like a fuel delivery problem or starving for fuel once under load
 
#5 ·
welcome call Woodbutcher and tattooedcat!! Rockerdude

I agree with what has been said and sounds like a fuel delivery problem. Checking the vent hose would be the easiest solution and then onto cleaning the carb, be sure to check all carb boots and connection. If the problem still presist after that then when it shuts done check for spark at the plug.
 
#6 ·
I had the same problem with my 400 last weekend too. It would idle but not take gas. If I let it sit for awhile it would run fine then all of a sudden run reallllllly rough. I wasnt getting spark(or not much) when it wouldnt run. I think from what I got on the forum here is that my coil is bad. I believe that more than anything. I went through the fuel system ALL Friday night. But it sounds like yours is doing exactly what mine did.
 
#7 ·
My wife's old 400 had a similar problem, but that was traced to a broken wire in the main wire harness from the stator plate coming out of the engine cases just below the carb. When it went in to a fit , a little jiggling of the wires cured it for a while , but I had to solder in a new wire after the ride was over . It was quite a little task, as you need to split the cases and get a new gasket to reassemble the engine.
 
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