Fuel issues - Polaris ATV Forum
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post #1 of 10 (permalink) Old 05-10-2019, 11:08 AM Thread Starter
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Fuel issues

Help!!!..I'm restoring (or trying to) a 1988 Polaris 250 Trail Boss..I had it running, a good idle ..I let it run for a bit and it speeded up by itself and stopped..It'll run while starting fluid is being sprayed..I assume it's not getting gas ..And I do still have the oil injection pump hooked up..And "NO" I'm not the best of mechanics but I enjoy tinkering with them..lol..Any suggestions. I'd appreciate it..Thanks in advance Pete
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post #2 of 10 (permalink) Old 05-10-2019, 02:13 PM
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Check the compression? Are you sure the injection pump is working? If all that is good then you need to start tracing the fuel flow to the carb. If you have fuel getting to the carb but not into the engine, then the carb has to come off for a good cleaning.
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Mine: 2018 Sportsman 850SP - 26" Bear Claw HTRs on OEM steel wheels(I really don't like the Aluminum ones)
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Hers: 2007 Sportsman 500 EFI, Polaris Winch, 26" Bear Claw HTRs on Moose 427x Wheels. QSC Clutch Kit, Hand Warmers
2001 Magnum 325 MOSE 12" rear wheel conversion. 25" Sedona Coyote tires
2001 Magnum 325 Warn winch and Moose 60" plow
2017 Polaris Ranger 1000XP - Roof and front glass
SOLD 2004 Sportsman 600 Twin
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post #3 of 10 (permalink) Old 05-11-2019, 05:44 AM
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Usually when the engine speed up just before it dies, it's an indication of the carb running out of fuel - it leans out, speeds up then dies - check the fuel delivery to the carb - make sure you are using fresh fuel and non-ethanol is best
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2006 Trailboss 330
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1971 Triumph 650 Bonneville (has 5 original miles)
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post #4 of 10 (permalink) Old 05-16-2019, 09:42 PM Thread Starter
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Thanks.i took the carb back off gave it a good cleaning..It'll start but will run wide open.. Backing out the "idle screw" doesn't help...Thanks again for the help...Pete
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post #5 of 10 (permalink) Old 05-17-2019, 05:35 AM
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The Slide is not closing completely - check the throttle cable to assure it is seated at all junction points - make sure the slide needle is not jammed in the needle jet - make sure the slide groove is engaged with the guide pin in the side of the slide bore - make sure the cable is adjusted correctly - is the idle screw you removed the speed screw or the mixture screw - make sure the carb is fully seated in the holder - check the carb holder for cracks - that's about all I can think of as potential problems

2006 Trailboss 330
2002 Sportsman 90
2005 TRX400EX (FOR SALE)
2003 LT-Z400 (needs engine work & is for sale)
2004 CRF250X
1971 Triumph 650 Bonneville (has 5 original miles)
1972 Triumph 650 Bonneville (undergoing restoration)
1979 Honda CBX (6 cylinder)
1970 Kawasaki G3SS 90cc Bushmaster
1976 Suzuki RE5 Rotary (not running & FOR SALE)
1981 Kawasaki KZ305-A
1981 Suzuki GS450T (undergoing repair & will be for sale when done)
1982 Kawasaki KZ750-H (FOR SALE)
1989 Honda VT1100C
2007 Vectrix VCTX Electric Scooter
1965 Montgomery Ward 3 1/2 HP Tecumseh Mini Bike
1970 Triumph T25 250cc Trailblazer
1968 Triumph 250cc Flat Tracker

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post #6 of 10 (permalink) Old 05-17-2019, 10:14 AM Thread Starter
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Thanks for the help..I'll go over all of the suggestions you made..Just curious? If I decide just to purchase a after market carb..The only thing that I need to know is that it is a 36mm?..Right?..My old carb is a Mikuni VM series 36mm round slide..I'm hope there's others that are interchangeable..Thanks...Pete
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post #7 of 10 (permalink) Old 05-17-2019, 10:33 AM
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Quote:
Originally Posted by OleMiss2019 View Post
Thanks.i took the carb back off gave it a good cleaning..It'll start but will run wide open.. Backing out the "idle screw" doesn't help...Thanks again for the help...Pete
If I were guessing I'd say the slide is turned the wrong way.
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post #8 of 10 (permalink) Old 05-17-2019, 02:04 PM
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Quote:
Originally Posted by OleMiss2019 View Post
Thanks for the help..I'll go over all of the suggestions you made..Just curious? If I decide just to purchase a after market carb..The only thing that I need to know is that it is a 36mm?..Right?..My old carb is a Mikuni VM series 36mm round slide..I'm hope there's others that are interchangeable..Thanks...Pete
I would not replace the carb unless you are gonna part with the big bucks for a new Mikuni piece. Check the posts on the forum. Way too many where they got a cheap Chinese knock off carb and had problems making their machine run right. Unless it is cracked or broken you are much better off to use the original piece.

Mine: 2018 Sportsman 850SP - 26" Bear Claw HTRs on OEM steel wheels(I really don't like the Aluminum ones)
Polaris Hand warmers, Mirrors.
Hers: 2007 Sportsman 500 EFI, Polaris Winch, 26" Bear Claw HTRs on Moose 427x Wheels. QSC Clutch Kit, Hand Warmers
2001 Magnum 325 MOSE 12" rear wheel conversion. 25" Sedona Coyote tires
2001 Magnum 325 Warn winch and Moose 60" plow
2017 Polaris Ranger 1000XP - Roof and front glass
SOLD 2004 Sportsman 600 Twin
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post #9 of 10 (permalink) Old 05-18-2019, 09:14 PM Thread Starter
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Slide turned the wrong way?..Could be it...I'll to tinker with it again..I thought if the slide fell in easily that it would automatically be correct...Thanks for the advice..
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post #10 of 10 (permalink) Old 05-18-2019, 09:27 PM Thread Starter
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You're probably right about the carbs from China..I'll probably keep my Mikuni and keep working on it..My problem is, I've always been frugal (some say cheap) lol.. Appreciate the advice though...
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