How's the air filter?

 

I think you are right that you can rule out the cam since the problem came on so fast. You can also rule out the clutch since the problem occurs in neutral.

I am not very familiar with your model, but after doing some more thinking I am wondering if your cam chain has jumped a tooth. You can have it jump one tooth and the engine will usually run but not very well. That would sure explain a lot of the problems you described - although I would think your neighbor would have found it difficult to adjust the valves if this happened.

Do you have any idea on how many hours or miles you have on the motor?

I would check to make sure your cam is still perfectly aligned to the crank. If that checks OK, then I would go back to looking at the rev limiter since it's free to bi-pass it.

I don't know how the decompression mechanism works on your machine but most of the automatic type keep the exhaust valves from closing completely at very low rpm (like the RPMs you spin the machine to when starting it). Usually a defective decompression mechanism (one that stays open) would make the eninge very easy to spin / start (since you cannot develop full compression). If the mechanism failed the other way, you would have full compression all the time - even when you go to start it. That would yank your arm pretty good. But, if the decompression is not working at all, it would not hurt how the machine runs, just make it stretch your arm or work your starter over.

 

Polaridoo,

Thanks for the reply. My Neighbor also has speculated that it could be the the cam chain skipping a tooth, but did not have the time to rip the whole motor apart to verify, so I am trying to eliminate all other contributors prior to having to do this.

As far as how many hours/miles, I am not sure. I bought the machine this past summer from the original owner. He thought it might have 2000-3000 miles on it, but based on the condition of the tires I would have thought less (although I did replace the tires with Mud Bugs as I wanted a little more traction).

The 1997 500 Xplorer (They only made it that year) is Identical to the 1997 Sportsman with one exception. To save money, it did not come with the handlebar mounted headlight/speedo pod. That is the only difference.

As far as the rev limiter, any ideas how to bypass it?

Thanks,

Mike

 

GE4x4,

Thanks for the reply. The Air Filter looks good, we also ran the motor without the airbox on, same problem occurs.

Thanks,

Mike

 

The 500 won't run without the airbox on anyway's, getting way to much air. Air filters are cheap and they have very simular symtoms of what you are talking about. Have you changed the filter since you got it? Getting to much or not enough air will make it sputter.

 

I am not sure how to bi-pass the rev limiter on that model. Maybe you can create another post just for that question? As far as the cam chain, I think you could check it without much effort. I think you would need to remove the valve cover and that might be it. I would think you could get the lower end aligned using the timeing marks on the flywheel. Once you have put the crank at TDC on the compression stroke you could verify the timing mark on the cam / sprocket. I know that was overly general instructions, but I don't have a 500 Polaris so it would be something similar to that.

 

GE4X4,

No I haven't replaced the air filter yet. When you say that it won't run without the air box, do you mean it won't run or it won't run well. The reason I ask, is that we did run it without the air box and when we got the higher RPM's and it started running like *+#$@*, it started spitting gas out of the carb intake. Is that what you would expect?

Look forward to your reply.

Thanks,

Mike

 

It won't run well without the air box. Air fuel mixture is what makes the engine run. With the air box off it will start but once you get on the gas it will suck in to much air for it to run right. On the other end if the filter is bad and it doesn't get enough air it will run like crap. My brother had a 400 Scrambler and had simular symtoms. He said his filter look allright. I told him to clean it or get a new one before you dig into anything else. Always do the cheapest thing 1st because many time that is the problem. Well he clean his filter and he could not believe that's all it took. I'm not saying it will solve your problem, but what I learned in atv class, do the simple things first.

 

just my 2 cents...did you try a new spark plug...same issue happen to me, would run great at lower rpm, went I floored it..it would boog, spit...slap a new plug in it..and away I went!

Just a thought!

Sbishop

 

To bypass the rev limiter just unplug the black wire from it.That will disable it but you will still have to use the button for 4x4 in reverse.