2004 Polaris Sportsman 600 Carb question

[n4cer26]

Hi guys!

I recently acquired a 2004 Sportsman 600 4x4.  It originally ran great but now It runs very rough and only with choke on.  It dies when you hit the throttle. I will be removing the carb for a good cleaning.  At this point I'm thinking it's a fuel issue.  I replaced the fuel pump and fuel filter today as they are cheap.  When I get the carb back we will see how it goes.  If it still runs bad I might try bypassing the fuel pump and running direct from tank to carb.  Any ideas as to what I should be trying would be greatly appreciated.

Also, the carb has two nipples in the front in the front on each side.  The left side has a vent hose on it but the right side is capped off.  Shouldn't this one be venting as well?  See pic.  

I did pick up a new aftermarket carb to have just in case.  There is a hose fitting on the right rear that my OEM carb doesn't have.  What would this be for?  I would think just keep that on capped? (See pic)

Thanksnin advance.

[Gwbarm]

I would check to make sure you are getting a good fuel supply to the pump and also to the carb, but from what you describe it sounds like a partially clogged main jet. The capped port appears to be a vacuum port for running a vacuum operated petcock, if you dont have that on your original carb just keep it capped.

[n4cer26]

Thank you for the advice and for taking the time! I really appreciate it!

[Cj Winds]

The second nipple that is capped off is another vent, same as the otherside. The carb only needs one vent to work properly. 

If the fuel pump is bypassed the machine will run out of fuel when the tank gets to approximately 1/3 full (just my guess) Fuel pump is used for when the fuel level in tank gets near level with the float bowl on carb.

I would not recommend using an aftermarket cheap carb, they are crap. The fitting is probably for the pulse line on the fuel pump. Rebuild original carb is best

 

[Gwbarm]

I would also recommend using the OEM carb.

[n4cer26]

2 hours ago, Cj Winds said:

The second nipple that is capped off is another vent, same as the otherside. The carb only needs one vent to work properly. 

If the fuel pump is bypassed the machine will run out of fuel when the tank gets to approximately 1/3 full (just my guess) Fuel pump is used for when the fuel level in tank gets near level with the float bowl on carb.

I would not recommend using an aftermarket cheap carb, they are crap. The fitting is probably for the pulse line on the fuel pump. Rebuild original carb is best

 

Yeah, I bought the aftermarket carb as a back up just to have.  I rebuilt the Mikuni OEM carb and it now runs like a champ!  Thanks.

[Gwbarm]

Thats great news, and aftermarkets are hit and miss some work very well. I have one on a suzuki now that is working very well, idles perfect runs perfect, but i dont go full throttle and act the fool like i used too, that is when you notice the difference.

[n4cer26]

18 minutes ago, Gwbarm said:

Thats great news, and aftermarkets are hit and miss some work very well. I have one on a suzuki now that is working very well, idles perfect runs perfect, but i dont go full throttle and act the fool like i used too, that is when you notice the difference.

Yeah, I have an aftermarket on an arctic cat quads.  Would have rebuilt the OEM but it was in terrible shape.  Couldn't get it apart, all the screws were seized up with stripped heads on them.  Drilled them out and the jets and were the same way.  The aftermarket carb is working perfectly.  The pilot screw was waaaaaaaay off so I adjusted that to spec and then installed it.  Smooth idle and lots of power.  Very satisfied with it!