Hello,

New to the board here-was hoping someone might be able to pass along any hints/suggestions on proper adjusting of a Mikuni slide carb on a water cooled Polaris 350 2X4. As best I tell, there appears to be 3 separate adustments: A small "wheel type adjuster(idle speed maybe?), the choke aduster? and a small slotted brass jet(mixture maybe?). All 3 of these are on the right hand side of the carb. The thing was barely idling and had very poor throttle response before I began my "meddling"....Now the thing is really messed up! Any help would be greatly appreciated!

Thanks!!!

Roger

 

The bigger wheel type adjuster is the idle screw.You may want to back it out a couple turns before you mess with it again.The small slotted brass screw is the air/fuel mixture screw ,you may want to screw that one in all the way then back it out one and a half turns then start the bike and see what happens.You shouldn't have to mess with the choke.Start the bike and if it idles to low then turn the bigger screw in ,till it idles like you want.Hope this helps.And welcome to the forums.

 

Thanks so much for that quick reply CED. Yes indeed, your tips will help! Not sure what to do with the choke adjustment since I've already messed with that too. When you back out on the idle mixture screw, does that result in a leaner mixture?

Thanks again

 

Yes it does create a leaner mixture.The choke cable has a small plunger on the end of it that sits in the carb ,and if it's not seated all the way down you will be leaking fuel into the carb creating a rich condition.It's kinda tricky but take your time and you will get it.

 

When I am adjusting/replacing the choke cable, I always screw the adjustment nut all the way down (choke fully closed/seated) - then with the engine running and warmed up, I start backing the adjustment nut out with the choke lever at 1/2 choke (1st latching position - straight out - full choke is with the lever at greater than 90* from off) until a noticable sound in engine operation is detected (almost like it is missing). Then if the engine is running right with the choke closed, I accept it as "right" and tighten the locking nut.

ps - the books don't go into detail on this adjustment.

on the mixture screw, if it is not right (too lean) the length of time to return to idle speed will be too long - from a snap open throttle it will not immediately return to idle, just kind of .... goes.... down..... to..... idle. A lot of times on the 2 strokes, the jet needle and needle jet in the carb get worn from the vibration of the engine (plain ol' old age), causing a too rich situation which will hinder the normal idle circuit due to excessive clearances on the needle and jet, and the only solution may be to replace both jet and needle if moving the clip position up on the needle does not work (the needle is tapered - so adjusting the clip position up lowers the taper farther into the jet - reducing the amount of closed throttle "gas" being sucked into the engine - be aware though, the clip position affects 1/4 - 3/4 throttle response too).

 

Great stuff! Sounds like the carb might need to be overhauled. Where could one purchase a rebuild kit for this carb?

Thanks!

 

Don't know of any "kits" available for the Polaris Mikuni's - I've always had to buy the individual parts (start adding $$). If you can find the Mikuni part #'s for what you need, you can get them from most independant shops (saves a little), or the easiest way is just order what you need from Polaris.

You might find what you are looking for at Partsland

 

You may even want to get some good carburetor cleaner or dip.Clean the carb real good then try it again.

 

http://oldmanhonda.com/MC/Rcarbs.html
http://www.atving.com/editor/techtips/carbclean.htm
maybe this can help.

 

Thanks for that link Quad! I've determined that the ATV is a '93 model. Its a 2X4 with the liquid cooled engine. Partsland has a listing for 2 very similar, but different(just a jet ring being the only diff) carbs. The part numbers for similar parts are different, so I need to determine which carb is on this thing. It doesnt say Blazer or anything other than "350 Liquid Cooled" on it. I would guess that the carb is the same one that comes on the 350 4X4 Liquid Cooled motor? Still having problems with it fouling plugs.

Thanks!