My 2002 700 Sportsman just started backfiring on decelleration. It won't do it when the engine is still cold but once it gets to normal operation temp it starts doing it. I had to replace the rubber boot (again, for the 3rd time in 1200 miles) that goes between the carb and the intake and I thought maybe I didn't seal it well enough so I took that off and reseated it. That isn't the problem. Anyone have any ideas?

Also- this quad has <u>always</u>, in my opinion, run very rich. The plugs are always black when I pull them out. I've tried the Champions and NGK- no difference. My friends '02 Yahmaha Grizzly 660 kills me in races and from what I've heard that shouldn't be the case. My quad will also "bog down" when climbing steep loose dirt (or sand) hills. It won't spin the tires and get stuck but rather runs out of power. Using low range would help but then I'd get stuck- these hills- especially the sand ones- require some decent speed to get up- more then low can provide. My buds Grizz makes these hills in high with no problem. Sure he gets stuck- but not due to loss of power! Any suggestions on this? I do have a AAEN clutch kit on this quad and that helped a little with the power issue but I am still not happy with it. I am getting close to the end of my rope with this quad and am thinking of getting the '05 Suzuki KQ to replace it but if I can get my Sportsman to run correctly I might just keep it instead of signing up for 3 more years of $200/mth payments.

 

Sounds like you are rich on the pilot jet and maybe the needle. You may want to lean your pilot one size down and see if that helps. In my opinion, the SP600 and SP700 come pretty rich in the slow speed circuit.

 

Well my first guess would have been the intake boot but you said you checked that. I have never heard anyone going through three intake boots before. The new ones that Polaris had made usually fix that. I wonder if you kept getting 02 intake boots. If not the intake boot I would have to suspect an exhaust leak or some sort of vacuum leak maybe the carb it's self. It sounds like you may be having carb problems that may have just gotten worse over time but I would give the exhaust a close once over just to make sure before you tore into the carb. It sounds like you may have to tear into the carb any way though. Also check to make sure the foam at the top of the snorkel is not blocking the air intake. I always just rip out that dam foam cause it is only a matter of time before that screws with ya.

 

As an experiment I took the airbox "lid" off completely to see what happened (to lean it out a bit) and the backfiring got worse! Could I have something plugging up my pilot (idle) circuit making it run lean on the low end? The quad did sit, unused, over about 4 months due to a torn CV boot that I didn't want to tackle over the winter. I did put StaBil in the tank and started the quad once every 3 weeks or so. When I finally changed the CV boot that is when I found that the intake boot was cracked and after replacing that had the backfiring problem. I wonder if having that gas sit in there all that time gummed up the idle circuit in the carb maybe? I think I am going to have to have someone that knows how to rip apart a carb and then properly tune it (jets, etc.) take a look. $ounds expen$ive...but you gotta do what you gotta do I guess huh?

 

Back firing on decell is always a lean condition of the idle circuit.
If you dont have an air leak, then try going richer, out, on the mixture screws. If the pilot jet was plugged... it wouldnt idle.
You can still be too rich on the mains, and adjusting the mixture screw wont effect the main jet.
When the air lid was off, did it run better, when wide open? If it did, then the main is too big.

 

Thanks for the tips everyone. I broke down and took the carb out today and drilled out the "tamper proof" brass plug covering the pilot adjustment screw. I found that it was only about 1/2 turn from closed. The Polaris service manual says that it should be closer to 1-1/2!! I backed it out to 1-1/2 and found that my problem went away! I had to turn the screw in about another 1/4 turn to get the idle back down but everything seems kosher with it now.

 

Great! glad to hear you found the problem.

 

Jack, I havent had any of your problems with my '02 other than the carb adaptor /boot being replaced recently. It was cracking and looked badly weathered. Dealers told me they havent heard of this problem.
I have NEVER had a problem with not enough power.

 

Id like to hear about your Power problem on steep hills and such. Alot of us with 400s were having the same problems, and had to go down a size or 2 on the main and the problem went away. This shouldnt be fixed by changing the idle circuit, since you are usually running full throttle or close too it for long steep climbs. This would be related to your main, and as I said was a Problem MANY of us were having.. Has it done this since new or just start all of the sudden, if it was since new, then I would without a doubt change my main (after checking the plug of course, but you said it was running way rich anyway). If it Just Developed, then Your Airflow is probably being restriced someway, I would check that also.

 

It's always done this. I've changed plugs about 4 times and ecah time they have both been very black with carbon. If I reduce the main jet size what else will I need to do in the carb to adjust? DIfferent needle settings or float level or anything like that? I am a rookie when it comes to working on carbs, that's why I ask!

Thanks!