Carb Rebuild still dies with throttle applied. - Polaris ATV Forum
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post #1 of 10 (permalink) Old 05-16-2019, 05:49 AM Thread Starter
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Carb Rebuild still dies with throttle applied.

Hey yall,
I have an 04 Sportsman 400 that I got a year ago. Rode fine all year last year. It did sit outside during winter and spring, with fuel stabilizer in the tank. A few months back I went to start it up to move the ATV and it wouldn't start. I researched for month what possible issues could be, and in turn did the following.

-carb rebuild (new parts thru out)
-new battery
-new intake box/boot and filter
-blew air thru petcock and gas lines (gas flow is good)
-drained gas and added new

Now, the atv starts up great. Idles great but when i give it gas, it does rev up but then eventually the atv dies and stops running. After it dies i can not start it again until i wait 5 or 10 mins. I have no idea what to do at this point in time other than going to a dealer which I do not like doing.

Any and all help will be appreciated.

Thanks in advance.
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post #2 of 10 (permalink) Old 05-16-2019, 06:37 AM
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Sounds like a possible fuel pump problem or an obstruction in the float needle of the carb - maybe not letting fuel into the carb fast enough - could also possibly be an obstructed float bowl vent

You say you have good flow from the tank - how is the flow through the petcock and what about fuel pump output?

2006 Trailboss 330
2002 Sportsman 90
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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
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post #3 of 10 (permalink) Old 05-16-2019, 09:17 AM
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Could also be mixture adjustments seeing how the carb was rebuilt. Waiting 5-10 min cools it back down so you then need a richer mixture to start it again. Also, rebuilding a carb now isn't like it used to be. This ethanol crap turns to gel and then gets hard in the tiny orifices throughout the carb. Sometimes letting the body soak in carb clean helps, sometimes you need to carefully mechanically clean out the passages.

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post #4 of 10 (permalink) Old 05-17-2019, 05:56 AM
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Quote:
Originally Posted by HawkX66 View Post
Could also be mixture adjustments seeing how the carb was rebuilt.
It's not the mixture screw - the mixture screw is for idle only - if it idles well, but dies at higher speeds it's probably a fuel delivery problem - check carb venting, fuel flow from the pump, fuel flow from the tank to the petcock, fuel flow from petcock to fuel pump or for an obstruction in the fuel inlet circuit from the outside of the carb to the inside of the float bowl.

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 #5 of 10 (permalink) Old 05-17-2019, 07:42 AM
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Quote:
Originally Posted by latebird View Post
Quote:
Originally Posted by HawkX66 View Post
Could also be mixture adjustments seeing how the carb was rebuilt.
It's not the mixture screw - the mixture screw is for idle only - if it idles well, but dies at higher speeds it's probably a fuel delivery problem - check carb venting, fuel flow from the pump, fuel flow from the tank to the petcock, fuel flow from petcock to fuel pump or for an obstruction in the fuel inlet circuit from the outside of the carb to the inside of the float bowl.
I wasn't referring to the idle screw. Idle isn't mixture. (edit: yes, technically speaking it is...) I'm talking about jets etc. Whatever these carbs need adjusted to change the lean/rich mixture. I haven't gotten into the carb on this one yet, but I'm sure it's jetting to change the adjustments. I don't know what he did to the carb to "rebuild" it. I still would say it's more likely the carb is plugged somewhere. Doesn't take much...

Semper Fi!
04 Sportsman 600 4x4
69 Camaro SS396
SLK350
17 Expy Platinum
07 Hayabusa
93 Harley FXLR custom
KTM 300 EXC
YZ 250
RM 250
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post #6 of 10 (permalink) Old 05-17-2019, 09:17 AM
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Quote:
Originally Posted by HawkX66 View Post
Quote:
Originally Posted by latebird View Post
Quote:
Originally Posted by HawkX66 View Post
Could also be mixture adjustments seeing how the carb was rebuilt.
It's not the mixture screw - the mixture screw is for idle only - if it idles well, but dies at higher speeds it's probably a fuel delivery problem - check carb venting, fuel flow from the pump, fuel flow from the tank to the petcock, fuel flow from petcock to fuel pump or for an obstruction in the fuel inlet circuit from the outside of the carb to the inside of the float bowl.
I wasn't referring to the idle screw. Idle isn't mixture. (edit: yes, technically speaking it is...) I'm talking about jets etc. Whatever these carbs need adjusted to change the lean/rich mixture. I haven't gotten into the carb on this one yet, but I'm sure it's jetting to change the adjustments. I don't know what he did to the carb to "rebuild" it. I still would say it's more likely the carb is plugged somewhere. Doesn't take much...
Sorry Hawk - I guess I just read 'screw' as most people have a misconception about the screw's function.

You are correct about the jetting and such. Metering the air is as important as metering the fuel. Those internal cross drilled passages are instrumental in carrying both fuel and air. Block one off or corrode a link from one to another and the device fails to function as designed.

And, yes, the alcohol causes many problems; clogging, corroding and changing the metering precision. Alcohol blended fuel usually requires allowing more fuel through the jets for proper performance. Generally speaking, turning the fuel screw out about 1 turn and increasing the main jet by one increment is beneficial.

Again, sorry I mis-read your post and tried to correct a point that you were not incorrect about.

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

Shop Owner and Mechanic with over 50 years experience

Last edited by latebird; 05-17-2019 at 01:58 PM. Reason: Context
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post #7 of 10 (permalink) Old 05-17-2019, 11:26 AM
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[quote=latebird;1427995][quote=HawkX66;1427983]
Quote:
Originally Posted by latebird View Post
Sorry Hawk - I guess I just read 'screw' as most people have a misconception about the screw's function.

You are correct about the jetting and such. Metering the air is as important as metering the fuel. Those internal cross drilled passages are instrumental in carrying both fuel and air. Block one off or corrode a link from one to another and the device fails to function as designed.

And, yes, the alcohol causes many problems; clogging, corroding and changing the metering precision. Alcohol blended fuel usually requires allowing more fuel through the jets for proper performance. Generally speaking, turning the fuel screw out about 1 turn and increasing the main jet by one increment is beneficial.

Again, sorry I mis-read your post and trying to correct a point that you were not incorrect about.
Don't be silly. No apologies necessary. I could easily have meant that. You were right. No worries. We're tracking...

Semper Fi!
04 Sportsman 600 4x4
69 Camaro SS396
SLK350
17 Expy Platinum
07 Hayabusa
93 Harley FXLR custom
KTM 300 EXC
YZ 250
RM 250
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post #8 of 10 (permalink) Old Today, 10:55 AM Thread Starter
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still learning forums so apologies if this reply is all over the place.

The carb was rebuild with all new internal parts and gaskets. Before reinstalling the new parts(pilot jet, main jet, i got a rebuild kit), i took an air compressor and blew air thru the entire carb all tiny little holes and crevasses.

I believe the engine is too rich, i googled symptoms of an engine running to rich and my ATV shows most signs.

-sluggish accel ( when throttle applied slowly it doesn't die)

-choke not needed for cold start (something i always needed to do before)

- strong smell of gas when idle.

I am going to adjust the mixture to the leaner end and see what happens.


Thanks Yall, i will update shortly .
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post #9 of 10 (permalink) Old Today, 11:53 AM
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I bought a used carb and rebuilt it and it didn't run properly. Bought a paint can of the carb cleaner from Advance Auto Parts, dunked the carb body and let it sit for a couple hours and magic. Runs like a top. I used carb cleaner and compressed air during the rebuild, and I only use no ethanol gas.

I don't need to use the choke to start mine cold when its not cold outside either. It starts right up just hitting start. I don't mess with mixture screw(s).
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post #10 of 10 (permalink) Old Today, 02:57 PM
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Sounds to me like fuel flowing to carb is slow like previously mentioned. Once you use up the fuel in the bowl, it stops running, then you wait for it to fill back up. Fuel filter new? I have same issue occassionallly with my daughtersí 90cc ATV. Take air filter off, start engine, and put your hand over air intake several (removing just before engine dies). This will cause a vacuum inside carb and hopefully suck through any small pcs of crud. Other than that, might need to take carb back off and clean thoroughly again.
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