I am currently chasing a very intermittent problem with my sons 2014 400HO. The machine will run fine then it will get a real rough idle and even stall and then be fine 2 minutes later.
I have changed the plug wd40'd the plug wire upped the idle slightly, I have changed the oil and filter and run seafoam through it several times. There is no vacum leeak showing (sprayed brake clean around the block)
There is no codes that I can see no warning or check engine light and the fuel pump seems to be fine any idea's? I am wondering if it has a fuel enricher or something. The machine will never shut down or run shytty with a load on the motor just when it idles down and a little when you try to rev it up????

 

Even though it's fairly new, a tiny piece of plastic/rubber or a bit of trash in the carb can cause problems. I've found bits and pieces of both. If it's bothersome enough I'd take the carb out and physically clean it. All it takes is for something like this to get under the float needle or float around in the carb bowl and get sucked up by a jet.Even a partially blocked vent line can cause problems. Here's a good pdf section from a shop manual on the BST34 carb on cleaning,float adjustment,etc. https://www.google.com/url?sa=t&rct=...,d.aWw&cad=rja

 

Thanks OPT I am leaning toward pulling the carb but I would like to try to adjust the throttle first.

 

Yes could be as simple as too much throttle slack that can cause problems. Adjust the cable to where it's no more than 1/8" slack at the thumb lever. You can check the etc switch to see if it is working properly. Just pop the throttle control cap off,while the engine is running have it just above an idle. While holding the throttle, reach in with your other hand and grab the cable before it goes into the throttle lever control wheel. Release the thumb lever and it should spring back causing the etc contacts to touch killing the engine.

 

Going to save the link... Thanks OPT.

 

This link to the fuel system manual covers most of the carbs Polaris has used on their full size machines from the two stroke VM30,VM34 carbs to the 4 stroke BST34 and BST40. Pretty good link to book mark if you need carb references,jetting guides,rebuild info,etc.

 

This is gonna be much easier now!!! Thanks for all your help, now if it would only stop raining or snowing for more than 1 day!!!!!!!!