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I have a 2001 Polaris 90 that has been sitting several years. I do have it running and it will sit and idle but will not pull off the majority of the time. I have replaced the carburetor, air filter, drive belt, and rollers for the front drive pulley. It will rev up and turns the wheels when on the atv jack and wheels are off the ground.
 

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Where did you get the carb? If it came from Ebay or Amazon, just get it jetted correctly and all will be good (hopefully - it depends on the quality of the carb) - just out of curiosity, what brand is the carb? What did you do with the old carb? I might want to buy it if you want to sell it.
 

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The new carb came from ebay, not sure of the brand. The other carb sat for an estimated 10 years with gas in it, and was beyond repair. The electronic choke plunger had seized and broken off inside the body of the carb. If it is the jetting on the carb then why would it rev up when elevated with no resistance to the rear wheels? It revs up and wheels spin really well when elevated off the ground.
 

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I can repair most "beyond repair" carbs - the only ones I haven't been able to repair are those severely corroded from water and physically broken by inexperienced novice mechanics. If you still have it, I would still be interested in getting it.

The reason it will rev with the wheels off the ground is because the engine needs less air and fuel to accelerate. Raise the wheels off the ground, lock the brake and it will respond the same as if the wheels are on the ground. As the throttle is opened it is allowing more air into the engine - the carb's job is to mix fuel with the air - if the engine bogs as the throttle is opened, it generally indicates a lean condition - it may be lean just off idle (pilot screw adjustment), in the mid range (slide needle position) or above 2/3 throttle (main jet) and it may require adjustment of more than one circuit to smooth the transition from one circuit to the next.

It may only need an increase of fuel in the mid range to make it run right - it may need an increase in mid range as well as the main jet - it may need a complete re-calibration of all three circuits for proper performance. The carb 'fits' and the installer is responsible for tuning it for the application. It's pretty simple, just time consuming - no shortcuts - each time the carb is removed and installed, the air box must be removed and installed also - the air filter must be clean and in good condition - the thing that complicates tuning the cheap Ebay and Amazon carbs is generally the installed jets are not marked as to the size. The jets may not be the same thread or design as the OEM carb so finding jets may be difficult and knowing what size to install is a crap shoot - if the installed jet is not marked you don't know what is larger and smaller than what it has and even if it is marked, it may not be the same measurement as the replacement jets you get. The thing I really hate about the cheap carbs is there is no quality control - buy 5 carbs and one might work with the rest not working right and of the 4 that do not work right, all 4 will not function in different ways - one will be lean at idle, one will be lean at full throttle, one will be rich at idle, lean in the mid-range and rich at WOT and the last one may be lean at idle and WOT, but rich in the mid-range.

It is more cost effective to but an OEM carb with marked jets and save the labor of re-calibration, but you don't have to buy OEM from Polaris. The vehicle was manufactured in China by AEON, DINLI, ETON or another manufacturer. You can buy carbs from AEON or other Chinese supplier for less than Polaris sells them for and still get an OEM unit. You just need to know who manufactured the vehicle and the brand name on the carb. It may have been a Mikuni, KunFu, Denki, Standard of Japan or other brand and can be replaced by the same brand or other brand, but some are built to higher standards than certain 'no name' models.

The Chinese do not have alcohol in their fuel. The carb is calibrated to run on 89 or higher octane non-ethanol gasoline. Perhaps just putting in 91 octane pure gas could solve the problem, but you will probably have to take the carb off and open it up - see if the main jet is marked and install one two sizes larger than the one currently in it. See what that does for it and then perhaps raise the slide needle 1/2 to 1 mm - with a little fiddling, you will have it running like new.
 

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I only use non-ethanol gas when working with carbs so I know it is not the fuel. Your response did remind me that I hadn't replaced the fuel filter and I know that had been sitting for years also. When I drained the fuel before taking the carb off today there was not much gas in it at all. I am going to check the jetting and replace the fuel filter in the morning and see what type of response I get then.
 
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