I have a unusual carb issue that's driving me nuts as well as the previous owner!! I bought this 2000 sp500 not running and in need of a cam, so I put a cam and a new rocker in it but the carb had issues,it would bogg at full throttle.I found that the original diaphram spring was MIA with a stinking holley vacuum secondary spring in its place?? I took one from a junk CBR carb and put it in started it without the airbox and it revved fine with no bogg but when I put the airbox in it would bogg and die "filter was clean" so I took the filter out the airbox and it still bogged,it would even bogg if just the plastic tube from the carb body to the airbox was connected??CRAZY I know.I decided to experiment further and found if I put my hand half over the tube in the airbox it would run so I took a unifilter and tie strapped it over the tube and it run great no issues and I've been riding it for 2 months like that.Today I finially got a oem spring and put it in the carb thinking the issue was with it and it made no difference with the filter issue.The carb is clean,floats are adjusted proper,mixture or air is at 2 5/8 turns,even adjusted the clip with no impact.Why wont this thing run with the air filter installed.The engine has plenty of compression and runs great.

 

What size main jet is in it and what;s your elevation? Did you replace the cam with the HO cam or the stock one?

 

I replaced it with a scrambler 500 cam, not sure about the main jet size?Any idea what stock might be? To many have worked on this 4 wheeler

 

hi, stock i beleive is 155, it was bogging under 45 deg at 45 mph,put a 170 in, its incredible past 70 mph dying to see what it does in warm weather.

 

I have a 95 magnum that is the same way i am @1300 ft i bought the wheeler from a guy @300 ft if you or any one knows or has an idea let me know i am stuck as well...

 

you probably need to rejet yours as well, but look at your spark plug first. if it's really black, then you need to make it leaner, if its white, you need to make it richer. also you might want to turn your fuel screw to 2 1/2 turns

 

According to the book, the 95 magnum at 1300 ft should have a 140 main, the stock 500 sportsman from 0-3000ft should have a 142.5 from 3000- 6000 ft a 137.5 6000-9000 ft a 130, however I put a HO cam in my 425 and it went from a 135 main to a 150 but I also went to a bigger 40mm carb, runs pretty good. I just had anotheer thought on the 500, if you put the HO cam out of the scrambler in it you need to put the 40mm ho carb on it also, my 425 wouldn't run right till I went to the bigger carb.