2001 sportsman 500 HO

What things would you suspect with a weak and a slightly changing idle rpm? I find my bike won't idle strong anymore and it starts hard unless I feather the throttle even when warm.I still have trouble using the choke to start it ,but once it starts , i have to take the choke off quickly or it starts to cough and sputter.
I'm thinking of checking the spark , leaks around my intake manifold, etc.I might replace the fuel pump diaphragms too. The battery seems to be charging fine but I don't use the bike much anymore anyways. I'm wondering if I'm charging well enough or if my ignition coil is getting weak. I rebulit the carb a few times now and the last one not too long ago so I'm thinking it's clean and my fuel is fresh with seafoam added.
What things come to mind with a weak and slightly changing idle?

 

Easy things first.Check that the wire spring holding the idle adjuster hasn't broken,cable laying on the starter.Had plenty of these do this. Change the plug. If that doesn't help,pull the fuel line from the carb,crank the engine over. Should be a steady pulse of fuel. If not,then actually easier to just replace the fuel pump assy than to rebuild one,plus rebuild kit's only about 10 bucks cheaper than the complete pump.. Spray electrical cleaner around the intake manifold. If leaking and idle changes you can hear it and smell it through the exhaust. Plus even though you cleaned the carb awhile back,doesn't take long for fuel to turn crappy in the tank even with some brands of stabilizer,plus fuel just sitting in the bowl can cause problems over a short period of time.

 

Hi OPT

I checked the idle adjuster cable and it's fine. I even squeezed the metal holder so it holds the **** tighter. I hear that the ***** can turn on their own sometimes with engine vibration.
I checked the spark plug and it looks real good. No carbon and the color is gray. The plug is an NGK-R BKR6E. Does that sound right? I measured about .032" gap (the manual says .024" to .028")
My idle doesn't change much when I'm sitting still idling, I just notice a change when I've been driving for 20 minutes or so and I stop to idle again. It's either higher or lower than the last time i listened to it.
In my videos below, I can see a definite "skip" in the spark while the engine is turning over. Could this be a faulty stator or possibly an incorrect pulse trigger gap? (manual says trigger gap should be .016" to .040")
I removed the fuel inlet hose on the carb and turned over the engine.The engine actually started with no throttle too?? (I did adjust my pilot screw back to 2 turns out from 2.5 before this) The fuel sure doesn't come flying out of the hose, it doesn't pulse either, just a steady SLOW flow comes out. Is my pump too weak?

Kevin

 

Pull the recoil cover and clean any dirt/mud accumulation(almost all get a little) on the flywheel and pick up coil. Check the pick up coil gap,you can even tap the bracket in a tad and see if it starts better.Seems to be a common problem on the 500 as they get older. Grease the bendix while you're in there. Seal the cover and recoil with a good rtv to help keep moisture out. Some fuel pumps would pulse other would have a steady stream of fuel.If in doubt they're cheap enough to just throw another on. Make a mark on the idle adjuster inline with the carb bowl and after riding check for any cable movement.Some have a habit of doing this. You can check the resistance on the pick up coil white and white/red wires also. Should be around 97 ohms resistance +/- 20%. If it's getting close to allowable range these are cheap to replace also.http://www.ebay.com/itm/Stator-Pick-up-Pulsar-Coil-Polaris-Scrambler-500-2x4-4x4-2001-2002-2003-/291200395560?pt=Motors_ATV_Parts_Accessories&hash=item43cce56928&vxp=mtr

 

Thanks OPT ! I'll try to dig into my bike in my garage this weekend. The weather is getting crappy out here now, so what better place to spend time in right?
Does the values I gave you for my spark plug gap and pulse trigger gap make sense? I want to set the proper gaps when I'm in there again...
I think I'll get another fuel pump for sure.....

Kevin

 

Manual does say .024-.028 but like a lot of people,I used em straight out of the box knowing their pre gapped at .032 without any problem. But if you wish you can close the gap a little and see if it helps. Plus if it's an older plug,change it,as something simple as a plug could be the cause of your problems. Pick up coil gap sound right.

 

I was able to get some time on it today. The pick up coil gap was larger than 40 thous for sure and the flywheel tab and the pick up magnet were both were dirty. Cleaned them up good and set the gap at about 22 thous. Hard to check with regular feeler gauges , had some brass ones lying around. Tried using a business card also but I couldn't find anything thicker than .3 mm (min spec is .4mm) Of course I forgot to check the resistance on it while in there!
It started with the electric start and a pull start. Both fired up right away. I then gapped the spark plug down to about 26 thous and it pull started right away also. Looks and sounds ok. I'll test it out this weekend hopefully.... I'm going to order a fuel pump soon too....just for peace of mind. I'll probably get a new spark plug as well for peace of mind. I'm wrenching on this thing way too much lately! Got to ride more than wrench!
Thanks for the link on ebay for the pick up pulser coil. Too bad the shipping to me in Canada is the same price as the coil... Ebay is a good spot to look though if I need to....

Thanks...

 

Sounds like you got it going your way. I'd still mark the idle adjuster against the carb bowl to see if it moves from vibration,especially if it idles down after you run it a while. Plus crank it up every now and then even if on a maintainer just to keep fuel circulating.

 

Got it for a half hr run tonight, everything works good. Starts easy, idles ok and I marked the idle adj. but only a short run so I'll keep an eye on it.
I think the cleaning and adjusting of the pick up coil gap really helped...thanks OPT!
Crossing my fingers for some long trouble free trips with the old girl now!

Kevin