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As many others have reported, I had similar problems with the engine randomly dying due to fuel related problems. Most of the time, the engine would start, idle and run without incident. Then, while riding, without warning, the engine would die. I used a shot of ether ("Engine Starting Fluid") to get the engine to fire but it wouldn't stay running. I knew it was a fuel issue, so I rebuilt the cabrurator. (Additionally, resolving several other issues- see my carb rebuilding thread--- http://www.polarisatvforums.com/for...r-rebuild-leaking-engine-lag-fuel-issues.html ).
[<Aside>-Thinking all fuel related issues were resolved, I took the Sportsman out to my 5 acre lot in the woods. The lot is undeveloped, one road leads to the lot but no roads, trails or paths exist on it (sourrounding lots also undeveloped). I had the lot surveyed and wanted to follow the property line, now that I could identify the boundries. The ATV peformed better than before, no 'bogging', smooth performance, climbing over downed trees, weaving through the heavy undergrowth, hills and up/down a 40' deep gully. I arrived at the very back corner of the lot and began to follow the property line out. While sitting on the side of a hill (right side down) the engine DIED! Can't repeat what I yelled at the Sportsman but it deserved it! The engine would not fire! (For some unknown reason, I had put a full can of "Starter Fluid" in the tool compartment. –I guess because I couldn’t find any difinitive cause for the previous failures)
I removed the seat, air box top and air filter and tied them to the front rack. I blocked the carb intake with the heel of my hand and hit the starter. Fuel gushed out so I knew the lines, bowel and filter were clear. <If the %$# holes at Mikiuni had just left the REAL 'choke' butterfly in, I would have been out of the woods in no time> I stood on the left footwell, sprayed a dose of ether, hit the starter, quickly opened the throttle and held on. Sometimes I would move up to 20', others just 1 or 2 feet. After about 20 times, I pulled the 'Fuel Enrichment' knob and found the engine would run at 800 RPM for 3 or 4 minutes but had very little power and would not rev higher (good for flat spots, I walked beside it on the way out). On hills, over tree stumps and logs: brake, spray, full throttle and brake again! After about 45 minutes, I was out. I put the Sportsman on the trailer, swor at it again and went home.]
There remained only one fuel component I had not replaced/rebuilt/cleaned. I removed the fuel pump from the left front wheel well. (Nice to turn OFF the fuel valve -new- and have the flow of gas actually stop! And what MORON would mount a critical fuel component with plastic automotive TRIM fasteners in a wheel well where the lines and pump are exposed to rocks, sticks and water/dirt/mud thrown up by the front wheel??? I can understand the attempt to limit vibration transmission to the fuel pump-prevent bubbles in the fuel and pump valve malfunction-all due to a POOR design, but plastic trim fasteners, REALLY! Ever seen a motorcycle, car or truck with fuel components exposed like this? NEVER!) After disassembling this 'Micky Mouse' pump, I poured out a 'palm full' of fine dirt from the breather chambers at the base of the pump. I noticed 'water marks' on the interior walls of the chambers. At that point I understood why the engine would die. When the ATV was at an incline, right side down, the dirt would shift and block the breather holes, effectively stopping the weak pump from operating, no fuel flow! I could see why they used small breather holes in an attempt to limit dirt/mud/water intake but it creates a new problem, dirt easily blocks the small holes and STOPS the pump from working.
If I raced the Sportsman or did a lot of mudding, I would replace the POS fuel pump with an electric, pressure limiting one!
In short: If your engine dies at random due to fuel issues: definately rebuild your carb (kit $30-Amazon), check your fuel lines (new $8-auto parts), fuel filter (new $7-auto parts), make sure your fuel valve isn't restricting flow (new ones are about $20 on the BAY) and check your fuel tank (drain to get junk out).
CAFEFULLY disassemble and clean that POS fuel pump, paying close attention to the breather holes in the back plate-see the diagram. (handle the diaphram gently). CLEAN the triangular shaped pump mounting plate! When you are reassembling, remember : first, cross torque the screws to prevent warping as the diaphram material is not compressable. Second, make SURE there is an air gap between the triangular pump mounting plate and the fuel pump base, to allow free air movement into/out of the breather holes!
Good luck.
 

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