[tlivingd]

Recently picked up a 1000 mile 03 Sportsman 600 from my FIL. It would run but fall apart at partial throttle backfiring out the exhaust. He took it in for service shortly before I purchased it, and they found one fouled spark plug. I then got it and it still would fall apart and backfire. I dug into it and found a cut in the rubber boot from carb to head but not though, and a chunk of something in the bowl. Replaced the boot and cleaned the carb, and inspected the diaphram.

It now starts great, however the exhaust at idle smells super rich. Immediately after going through the carb, puttering around the yard it was ok thought i didn't have a problem and now after sitting for a week it again falls apart just giving it gas and during partial throttle till you get going a little faster then it seems ok. If it's super warmed up it doesn't seem like there is a problem. I haven't pulled the plugs yet.

I was thinking ignition related but as I type this I'm wondering if the float is partially sunk. (I don't notice fuel coming back into the air box.) I'm also thinking I could try to tweak with the idle air screw but after that I'm out of ideas. I'm not terribly knowledgeable on slide valves so if there is something else to look at let me know.

Anyone else have thoughts to what I should look at before dumping a ton of money into an ignition system. (it's the OE Ducati ignition that I've read were problematic.)

Nate

 

[Flintlock52]

I would exhaust the fuel system fixes before diving into the ignition. The 03's did come with the bad ignition systems but when they went bad the atv wouldn't crank or even turn over, yours isn't doing that.
That rubber boot should be replaced first.Then crank it again and see how it runs.
Buy a good rebuild kit and completely rebuild the carburetor including the needle and slide. Drain all the old gas from your gas tank and replace with fresh gas and go ahead and mix fuel stabilizer with new fuel also. There will be a air fuel adjustment scew, replace with one from kit. Turn this screw in until it touches the other side, then back it out 1.5 turns.
If the machine cranks then lit it sit and run for about 10 Min then set your idle to 1100 RPM.
This should fix or improve the problem. If not buy a new float and set it carefully.

k

 

[Flintlock52]

About that float......my 2003 SP600 has a funky looking float, the top of the float is not level with the top of the carb. but it's on an angle. I did some research and haven't found another float that looks like this one. On top of the float is a stainless plate. I picked a spot and marked both sides of the plate. This is where I measured from, taking care that both sides were equal. After setting it best I could examination showed what looked like adequate travel on both top and bottom to hold an adequate amount of fuel.
Part of my test drive was a fairly flat, clean powerline, I had also replaced both spark plugs and when I dumped the throttle it pulled so hard I could feel it trying to come out from under me. So for me, I consider the way I set the float height to be correct.
Just thought this might help a little.