bought a 98 polaris xplorer 300 4x4.... sat a long while before i got it.
rode it approx 15 miles and blew it up. moisture in crankcase and torn seal. also seemed to be lacking oil.
rebuilt engine, top end \, crank bearings, seals, bored < etc...

started it up and idle would stay high for 20 seconds and then drop to what it should have been. take off seemed to have a bog.
rode about a mile. took carb off to clean and reinstalled carb. started great but had to play with throttle to keep running. then it started to backfire and pop. both intake and exaust.
bought and installed carb kit today and seems to back fire worse than before. it wont run without playing with throttle and after it stalls it seems to be flooded.
is it a timing problem?
is it getting too much gas and causing the backfire?
it popped so bad that it caused the exhaust to come appart. lol
please help, mike

 

Make sure the throttle etc contact points aren't touching at idle. Usually on the older ones thumb throttle needs to have very little slack,about 1/16-1/8" free play.You can pull the top cap off the throttle housing and look at the contacts. Next thing is to pop the front panel and pull the black wire from the reverse limiter(left small module) these are notorious for shorting out and limiting,popping back,etc even in forward range.I've had em pop back and blow exhaust head pipes off the muffler also. Makes quite a noise. Item #28 Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse

 

thanks, i will check into those.
before i try to start again, can i get some information on the carb settings?
should the slide be at the bottom and then adjust the slack in cable?
or rest on the idle screw adjuster and then adjust the slack in cable?
where is a good starting point for air idle screw? before it blew, was only 1/4 turn out

thanks, mike

 

Just have the carb slide on the idle adjuster(if you haven't tampered with it) then adjust the slack at the thumb throttle by loosening the cable lock nut and turning the adjuster to where you have about 1/8" slack only. Air screw normally is 1 1/2 to 2 tuns out from a lightly seated position. Make sure the oil injector line on the left side of the carb is secure.

 

ok.. the throttle saftey is working correctly as is the limiter.
it would not idle on its own and the only way i could keep it running was to turn the idle adjustment all the way in and turn the air idle screw in to 1/4 turn out.
the quad did not get the rpms it should have for being set at that high idle. until it warmed a bit, it was pulsing up and down like a fuel problem. very little backfire at first then none with carb adjusted.
with carb set like this it has a bog coming off idle but high end revs quick and smooth.
do i need to set the slide to a certain height then adjust my cables to fit? there seems to be very little play at the moment.

 

With the carb set at 1/4 turn out you're basically leaning down the air mixture to get it to run. Retrace you're steps on the carb,recheck compression,should be at least 135- 140 on a new bore. You could have problems with an air leak. See if these videos help on the Mikuni carb.

 

thanks for the videos. i just dont understand why i have such a low idle even with the idle adjustment screw all the way in.
if it runs best with the air adjustment 1/4 turn out and im leaning the mix, it must be flooding with gas?
the main jet is clipped in the middle slot. what is the factory spec?
im gonna tear the carb back down again for another check and cleaning.
thanks, mike

 

3rd position from top is normal setting on slide needle clip. Some times on the older models as vibration wears down the slide area where the throttle stop screw(idle screw) hits,the screw tip wears down or the slide wears down to where the adjuster screw can't lift the slide very far. Cut the spring down a little if you have to and see if this helps. Make sure the float arm isn't wobbly and worn along with the float pin. These two items are not in the carb kits and a lot of people over look them! If it's worn it can stick and cause too much fuel in the carb bowl.

 

in addition to what opt mentioned above, a lean carb will also cause backfiring & popping. sure you have the proper jet kit in there since it got worse after you replaced it?
If it is in fact flooding, some pilot jets use o-rings to seat the needle jet- people often don't know there's an o-ring in there and end up blowing it out when using compressed air to clean out the jets and never realize it-
if that o-ring is missing, it'll flood out. Are you certain that all of the mixture jets you removed and cleaned were reassembled properly (springs, washers & o-rings, if relevant?) like opt mentioned- missing an o-ring or washer will cause an air leak and cause your stated issues...
Is the float level correct?

as we learned a while back (opt ) never assume the obvious has been ruled out... how's that air filter look?

 

already installed a new carb kit, new air filter, and new oring on the intake flange. i checked the float arm to make sure it was correct.
cylinder was bored 0.50 overstock and i was told to mix the gas as well to make it a 25;1 mixture for break in purposes.
a friend told me not to mix the gas (not needed) and that could be the flooding/rich problem. he also said to adjust the clip on the needle higher and possibly change the jet.
i installed a stock carb kit and clip is in the middle setting.
Any thoughts on friends advice?
should i premix my gas? or adjust the needle clip?