Any and all sugestions welcome.
Any idea why at wide open throttle (WOT) it starts to spit and sputter?
Things I've done and checked:
After I noticed it.
1. Pulled the K&N for cleaning, replaced with OEM.
2. Pulled plug on exhaust for cleaning. Nothing came out, even after running a hanger up in it.

Before it started.
1. Recently adjusted the valves to .006".
2. Was in some preety deep GA red clay.

Thanks
Kuntry

 

Full Throttle is on your main jet in your carb. Has the temp went up or down more than 30 degrees? Could also be your adjustments on your valves, recheck. Hope you resolve this, let us know. Good Luck.

 

Don't think it is the valve adjustment, earlier in the day it ran fine. I'm kinda leaning towards a fuel, exhaust or air intake problem. For what its worth one of the exhaust valves was way out of adjustment, almost a 1/4" after 1445 miles. Its probably a good thing that I checked them.

Kuntry

 

im pretty sure the sp500's have some sort of stuck throttle limiter, to prevent it from going out of control when its full throttle for a long time, that could be it,
or, like my freinds 2000 sportsman that he got a month ago and has been in the shop 4 times (broken linkage, oil leak, "to much play in steering", and somthing else) it was built on monday, or friday,
im not ranking, because im buying a 95 scrambler 400 today, what a gamble, but if it runs good, its mine

 

I hate to say this but I think your cam is failing. Take a look close look at the exhaust lobe and rocker for wear. Early Magnums and some Sportsman had some cam troubles.
The fact that your exhaust rocker clearance was 1/4" off tells me your exhaust lobe is going flat. Clearances normally will not change like that unless it was loose from the start or a failure like that.
Charlie

 

I am not familiar with red Ga clay, but I have a suspicion it is fine dusty stuff, that gets gooey when wet. If this is the case, I have one more thing for you to try. Find a long SMOOTH place to try this again. Go wide open, and when it starts to sputter, loosen the gas cap somewhat. What happens is sometimes dust can work into the gas tank breather, and plug it up to the point air can't get in the gas tank as fast as the gas is being sucked out, starving the carb for fuel. Sometimes you will think you are running out of gas, so you will stop, look in there, think there should be enough, and then it will run fine for a while before it does it again.
You can also stop as soon as you can after it starts to sputter, shut off the engine, and loosen the gas cap. Listen VERY closely & if you hear what sounds like air rushing in the tank, that is your problem.

Also, check the fuel filter as they will plug from time to time.

 

Last weekend I had a similar problem on my 00 SP500. I was towing a friend, and under load, it was sputtering and popping like crazy. I had just bogged it down riding in the river too fast and too deep, so I figured I had water somewhere it shouldn't be.
My friend gave it a good look-over and noticed that both bolts that hold the carb to the engine had vibrated off, so there was nothing holding those two pieces firmly together. Thankfully one of the bolts was stuck somewhere lower in the engine, and it ran the rest of the weekend fine with only one bolt.


Scott

 

Thanks for the help ya'll. It seems there were several problems. The water seal around the top of the head for the plug was kinda loose allowing some water in. the second was carb vent tube was kinked. I'm not sure which was the culpret but it doesn't do it any more.

Kuntry

 

Tell us a little more about the valves being 1/4 inch out of adjusment?

How could the engine even run?

 

Yes, please, I need to know about the 1/4 INCH. Wow . . . if all it does is sputter, consider yourself very fortunate.