So my 2001 Sportsman 500HO is giving me fits. Before I dive in to everything, just want to get a general opinion, and also have a shorter hunting trip planned for the weekend and won't have time to really dive in prior to that.

Facts are this, it won't idle without choke on and when up in higher RPM's it runs good with choke and without choke. It does backfire out the exhaust when you rev it hard. I have completely disassembled and cleaned everything in the carb (had water in there when it got put away last year and sat for 6 months), however nothing was replaced as Amazon decided that shipping a carb rebuild kit to Alaska is considered hazardous.

I know the infamous exhaust lobe failure on the camshaft, however, from all my reading, I thought the 2001 didn't have that issue as much. I have a carb rebuild kit shipping to a friend in the lower 48 and then they are going to forward it up, but it won't be here by this weekend to try replacing parts. Up until it was parked last year after starting this issue it ran great and had no signs of backfire or idle problems.

My question is this: would it be worth paying the polaris dealer prices for carb pieces so it runs better for this weekend or does this sound more like a cam shaft issue? If its the camshaft, I am going to baby it through this trip and then replace that after the weekend.

Just looking for some other opinions on it.

Thanks!

 

take a look at the cam to rule it out..but with water sitting in the carb, even tho you cleaned it, there might still be something in there

 

Parked for this long with no stabilizer and you'll have problems unless you have access to non ethanol fuel.Even if you do water can still accumulate over time and settle at the bottom of the tank. Flush the tank if needed,double dose with Marine Stabil, StarTron or other good stabilizer and run the devil out of it and see how it does.

 

Forgot to say I drained the entire fuel system out and added fresh fuel and ran some sea foam through it, however I didn't replace the filter or pump. The only reason I question it being the cam is the choke to idle issue and when it backfires it's not through the intake but the exhaust. Can the cam issue have those symptom? I'll try to check the cam but in order to get to the valve cover on this one, headlight pod, plastic and gas tank all have to come off. It was worked on by a shop last year with a no start problem, (ended up being an electrical harness shorted out and stator) and I had asked about the cam and they said it looked good a year ago with only a few hours riding in the last year.

The other thing I noticed, the throttle module that is mounted above the throttle. It idles pretty well when the electrical contacts in that module aren't touching without choke. If they are touching, it needs choke to idle, albeit at about 1500-1700 rpms.

 

The etc contacts in the throttle housing must be open or the machine can die or back fire if the throttle is suddenly released and the contacts "bounce" against each other or completely close. 1/8" slack only at the thumb throttle.Any more slack than that and you can have problems. This was and still is a common problem that a lot of people have and adjustment is shown in the owners manuals.

 

Wow, I had no idea. This might be my entire issue? My throttle cable is pretty well worn at this point. I will see if I can play with that tonight.

 

ahhh...sounds like a clogged idle circuit...opening the choke adds more fuel (bypasses the idle circuit)...they tend to have very small jets with tiny little holes...did you do a really good cleaning of the carb? I just started using an ultrasonic cleaner...I mention this because I thought I was doing a good job of cleaning my carbs, then I put a "cleaned" carb into the UC...ahhh...it really wasn't clean

 

Yeah, I'm sure it could use either new parts or an UC cleaner, one of which I can get before the weekend.

Which jet is the idle circuit?

 

Or better stated. What parts at a minimum should I throw at it to see if I can get a better running machine by tomorrow night? :-D

 

#36 is the pilot(idle) jet.Located right behind the main jet. This is a funky carb on setting the float height right. Look over this good write up on this BST40 carb used on a Ktm. A little different on the exterior but the guts are the same.The BST-40 Bible | Adventure Rider