2001 Polaris Sportsman 500 HO.


The ATV is bogging down--under load and not under load. It runs fine for a little bit but eventually the problem materializes. I pulled the air filter box off and under a heavy throttle I see oil coming out of the hose on the driver side and gas/gas vapors coming out of the passenger side hose. Is this normal?

 

What about the oil tank? Is it over full,does it have a gas smell to the oil? Plus have you ever changed the inline filter from the crank case line? Plus have you installed a carb kit recently? May be what it needs.. Plus with the air box off,the Sportsman 500s will run crappy and bog even if it was running great before you took the air box off.They're jetted for the air boxes and filters in place.

 

[QUOTE=old polaris tech;3324355]What about the oil tank? It is a little over the "normal range". Is it over full,does it have a gas smell to the oil? Not that I can notice. Plus have you ever changed the inline filter from the crank case line? No. Plus have you installed a carb kit recently? May be what it needs.. Plus with the air box off,the Sportsman 500s will run crappy and bog even if it was running great before you took the air box off.They're jetted for the air boxes and filters in place. I could tell no difference between the air box on or off.

 

No difference with the air box off or on,then I'd definitely look into the carb area first. Plus wouldn't hurt to check the intake manifold and carb support brackets. Some models were actually bad about the supports pulling the carb out of the intake manifold a little and this can cause air leaks and bogging.

 

Great. Thanks for the advice. I am now a firm believer that these are disposable units. All I do is work on it. I kind of wish it would catch on fire so I have no choice but to scrap it.

 

Have you ever been in the carb since you've owned it or installed a rebuild kit? If you haven't then I'd say 15 years is a pretty long interval. Plus a 15 year old machine will need up keep and repairs. Same as an old car.

 

I agree with maintenance. I have a couple of 1966 cars I have restored. They get driven way more than the ATV--and the ATV gets used once a week at most. I work on the ATV probably in 500-1 ratio to the cars. My friends with Hondas have no where near the problems I do.


Is it a big job to take the carbs out and rebuild them?

 

Not really. This is main fuel section from the manual and shows the basics on your BST34 carb also.https://www.google.com/url?sa=t&rct=...U2gGlaHJWSIlbA This Shindy kit is about the best out.Made in Japan for this Mikuni carb.Polaris Sportsman 500 Carburetor Repair Kit Fits 2001 2002 Carb Shindy 03 408 | eBay Plus there's some fairly good videos out there for Keihin and Mikuni cv carbs that can help you become acquainted with them.. One correction that i missed!! You have the BST40 carb which is similar to the BST34 except for the float setting. Here's a good section on these carbs as the float is different and setting is different.This carb is from a Ktm,but similar to ones that Polaris uses.The BST-40 Bible | Adventure Rider

 

Thanks again. Before I get to digging into the carb I have a couple questions"


1. Is the oil shooting into the air box normal? How about the gas?
2. I recently replaced the stator. Could that be a cause?

 

Oil shooting oil into the air box isn't normal. Could very well have some to do with the oil tank level being over the normal range and that could be because of excess fuel contaminating the oil. That's why I recommended the carb kit first so you could eliminate it as a problem area,plus replace or blow out the inline crank case filter that leads to the air box. Change oil and filter if need be and go from there.