Well fellas, I need a bit of help with this one again if you don't mind. A few months ago I posted about a sportsman that I was working on. It had a bogging problem. It idles fine, and runs low RPM ok, but as soon as you start to accellerate, even in nuetral, it bogs real bad and you can't get the RPM's up. When I take the air box apart and take the filter out it is a little bit better, but still bogs. I am thinking its gettig too much gas???
Last time I replaced the float needle, and adjusted the level of the gas in the bowl and it ended up running really well for me. Now it is having the exact same problem. I used a hose to check the level of the gas in the bowl, and it is exactly the same hight as the seam between the bowl and the rest of the carb. That is correct, right?
Now, I was thinking, is there any chance that this could be something as stupidly simple as a bad spark plug, and I am overlooking the obvious? I didn't think the plug could be the problem because of the way it runs better with the air box open. I am really strapped on time lately so I am hoping someone here can give me a tip to get this thing rolling again. I appreciate it!

By the way, this is a 2001 Sportsman 500HO.
Thanks!

 

I would change the plug anyways my 99SP was bogging last summer (the plug was 4 years old) and it fixed it. If you get a plug don't get Champion as I noticed no improvement.

 

Just a thought, I had the same problems with mine. I cleaned the carb, new plugs and a new filter. Gave up and pulled the engine. I have a worn out cam and exhaust rocker. Looking at past posts here it looks like Polaris had a problem with the HO cams and them wearing out too quickly. Just a thought.

 

hello
I just had this happen on my 98 sp500 after a lot of looking I found that there is a metal plate(9: JETBLOCK ASM) that slides up and down
in the carb It's the first thing you see when you look in there' mine was stikking and would not move up when you gave it some gas. IT would run just fine but when you gave it gas it would sputter and not run over idle level'
It would also corbon up the plug instantly.when I spraid the carb and worked the slider with a finger It fixed it right up
good luck man
after I fixed it I made it 3 miles from home and blew out a u-joint in the rear.*** lol $200 and back on the trail!***

 

Start it up. Open the throttle to get it to bog down. Hold it open for at least 10 seconds or so.
Continue to hold the throttle open, and shut ignition "off". Pull plug and check it. If it is wet, you're either getting too much fuel, or not enough air (as stated above). If it is dry, then it may be that the valves are not opening enough, due to improper valve adjustment or wearing of the cam lobes(also stated above).

 

i had that same problem with a 2004 sp 400 it was the vent line off of back of carb dirt dobbers had it stoped up i cleaned out and it ran like new again. there is three line in back of carb this one was stuck in frame on left side

 

Similar problem with the solution.

This might be your problem

 

check the breather lines on the carb i have had mine do the same and it was those lines. on my 06 500HO there is two off the back at the top of the carb. folllow them or the one and make sure they are clear, pull them off the carb and see if you can blow through them. also is your vacumn line to the fuel pump good? could have a pin sized whole in it and would be sucking air. Also is your diaphram good above the slide block??

Erik trailblazzers@shaw.ca

 

Well,
I checked a few things out tonight. Checked all the vent lines & the diaphram in the carb, all were good. I put a new spark plug in. I tried what IdahoVinnie said and held it wide open for 10 second and let it bog, and when I pulled the plug it was completely dry.
I pulled the valve cover to take a look at the cams. It appears that the larger lobe, (the middle one) is worn down pretty good. What and where should I be taking measurements? Im not used to working with cams & rocker arms because snowmobiles don't have them! (not yet) I replaced a camshaft a few years ago. Do you take the valve clearance measurements between the rocker arm contact and the top of the valve stem when the rocker arm is up all the way?? Is there an acceptable amount of lobe wear, or is the camshaft shot is the lobe has visual wear like this one does?
Thanks for the help guys!

 

You check the valve clearance where you stated, with the cam lobe rotated to the opposite side of the rocker contact point.

Any wear of the cam will decrease the distance and duration that the valve will open. The more the wear, the greater the performance loss will be. It sounds as though your cam is shot, but that depend on how badly worn that it actually is. Can you post a picture of it?