[Greatwhitehunter]

Hi everyone,
I am new to this whole forum thing and I do not know if this right place to be asking these questions but here is goes it is a long story, sorry in advance lol,
Okay I have a 1998 Polaris sportsman 500 it ran great then it was stolen three years ago and I ended getting back but when we found it the individual crashed it into a ditch it was submerged in water. I cleaned everything out and it would not run, so I called the local Polaris dealer and they told me to unplug the CDI box, the black wire and see if it runs, and it did so I wired in a taggo switch in there and for the last three years that is how I allowed it to start and that is how I shut it off. have not had a problem. two weeks ago I got it stuck in the snow and like an idiot I got it stuck and was horsing the crap out of it. I finally got it by using the winch and realize it was very loud and running like crap but it idles great. So I tore thought it was backing firing because it was leaking exhaust so I put all new exhaust on it and it was doing the same thing, so I checked the spark that was fine, I cleaned the carb and that was fine, so I started doing research and found that people are saying it is the exhaust Lobe 100 percent just change it that will be my problem. but wont I run into problems one I open up the motor? and everyone is saying to replace the camshaft with the HO 2001+ camshaft... but then some people say that I will have to change the carb from the stock one to a 2001+ 40mm carb... I just don't know so I figured I would post on this forum and see what you all have to say. I know it is old but it ran great I have replaced a lot of stuff on it to just junk it... help please

 

[Unlimitedor]

Pop the valve cover off and check the center lobe. It will most likely be worn. Check ouy ebay for a new cam as they dont produce the non ho cams anymore. You can install the cam without opening the motor up. As far as the carb put one size bigger jet in it and run it.

Sent from my SPH-D710 using Tapatalk

 

[Bruce!]

Welcome to the board!

 

[jgue498]

i got a 98 sporty too

had similar problems (as far as backfiring) but it was NOT the exhaust cam like everyone online said, so don't assume, you know what happens! Ok here's the deal, carbs on these units have 3 stages. First stage is used to start & idle, so i'm guessing yours is ok on this stage? Second stage takes up after idle and goes to about 12-14 mph, is this where your's stumbles, backfires? Then stage 3 takes up where 2 leaves off. Mine did fine on the first 2 stages, then would backfire as i would attempt to give it more throttle. The backfiring came out from between the 2 pipes held together with a spring (front of engine). Mine turned out to need several small parts like jetneedle, screws and the jetblock assemble. This part was bent on mine and would not move smoothly all the way up/down. Odd part is my quad was running great (up to 60mph) then suddenly this happened. No idea how but after replacing parts and tuning carb it runs great again. So check out your carb more closely. Good luck!

 

[Unlimitedor]

Take the airbox lid off and fire the engine up if it backfires through the carb its the cam

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[EricW]

If it starts and idles great you might check the TSS (throttle safety switch) just inside the cover above the thumb lever. What you will see in there is a set of contacts that look like distributor points that are designed to disable the spark/timing of the engine if the throttle position/cable shows anything off idle and the thumb lever in not depressed. Once you open the cover and cycle the throttle a couple times it will all make sense, then you can adjust it until it runs right off idle. Might be a possibility it got wet or corroded. Mine just stretched over time and got out of adjustment. It will make the motor respond like it does in reverse if you don't press the override button.

Worth a look, hope it works. EW

 

[Brentski]

1998 sportsman 500 backfiring through carb

Hi everyone,
I am new and am in need of help figuring out how to fix my 98 sportsman 500. I have torn the carb apart several times making sure everything is clean and working as it should. I hve tken the valve cover off and im trying to see if the timing is ok and also if the cam is ok. My ? is does anybody know what i need to look for to make sure they are ok? Thanks

 

[Brentski]

Hi I am new to this and am in need of some direction on my 98 sportsman 500. It backfires through the carb when I try to give it gas, I have torn the carb apart several times to make sure its good and I also have taken the valve cover off. I need to know what to look for if the timing is off or the exhaust lobes are worn. Any help would be great! thanks

 

[jgue498]

Fellow '98er

backfiring thru the carb Can be indicative of a bad exhaust cam (cuz it can't get out any other way). See the pic below when you peek at your cam lobes, the middle one is the exhaust cam (1 big one for both valves) and is the one that wears down, see how this one is much smaller in the center than the other 2 lobes?

I haven't done a timing check but know the technical guide has info on that. Lets see where is that thing? ah here we go:

File xx: Polaris Factory Service Manual for ALL Polaris ATVs 1996-1998
File Name: 1996-1998_POLARIS_SERVICE MANUAL.PDF
File Size: 50.19 MB
Download Link: Download 1996-1998_POLARIS_SERVICE MANUAL.PDF from Sendspace.com - send big files the easy way

Luck! :banana: