Sportsman Engine Noise through Carb

[number52]

Have a Polaris Sportsman 500 and it just started making a horrible sound through the carburetor. It starts just fine and idles great, but when you give it throttle it boggs and makes a horrible sound coming through the carburetor into the airbox. Took the airbox boot off and it sounds like the exhaust is coming through the carburetor! Any ideas?

Thought it might be the diaphram slide stuck in the carb, but it's not.

[CSR400EX]

that sound is probably the engine sucking air through the carb which is normal, the only reason you hear it is beacuse it bogs out. have you cleaned the carb out yet????

[250exkid]

buy honda foreman 500 s with footshift problem solved.... or a foreman 450s u cant out mud me..... check it polaris is to heavey and automatic not to diss u man sry but heres a pic

[number52]

Originally posted by 250exkid
buy honda foreman 500 s with footshift problem solved.... or a foreman 450s u cant out mud me..... check it polaris is to heavey and automatic not to diss u man sry but heres a pic

I totally agree! But this isn't my bike. Anyone else have a better idea than this one.

[number52]

Originally posted by CSR400EX
that sound is probably the engine sucking air through the carb which is normal, the only reason you hear it is beacuse it bogs out. have you cleaned the carb out yet????


This is not a normal sound. It's probably 10 times louder than what you're talking about.

[250exkid]

ummm go on ur carburator and theres air fuel screw i had that pop out of my old 4wheeler a couple times and it bogs and makes a loude air thrushing sound... it should be on the bottom of your carb its the screw if you pipe it and jet it your suppose to put it all the way in and back it out 2 1/2 turns out. hope this helps

[CSR400EX]

Originally posted by 250exkid
ummm go on ur carburator and theres air fuel screw i had that pop out of my old 4wheeler a couple times and it bogs and makes a loude air thrushing sound... it should be on the bottom of your carb its the screw if you pipe it and jet it your suppose to put it all the way in and back it out 2 1/2 turns out. hope this helps
if im not mistaken, and if the sportsman 500 uses the same style CV carbs like the 400 sportsman, the air fuel screw is blocked off on those mikuni CV carbs. its just a plug over the screw. have u tryed cleaning the carb out yet?

[number52]

No, just trying to get some opinions before I dig into it. Haven't heard many good one's yet though.

[250exkid]

kk

[450rdr424]

i worked on one with the same problem, made almost a backfire noise through the carb and airbox, hate to say this but when the guy took it to the shop it had a bent rocker arm and something else in the head was bent.....

[number52]

I was thinking it's more of a timing issue too. Thanks

[450rdr424]

fill me in when you do find out what exactly it is out of curiosity,

[86 Quad R]

it is also a possibility that the intake valve is stuck, bent, lost its seating or burnt.

[John451]

Originally posted by 250exkid
ummm go on ur carburator and theres air fuel screw i had that pop out of my old 4wheeler a couple times and it bogs and makes a loude air thrushing sound... it should be on the bottom of your carb its the screw if you pipe it and jet it your suppose to put it all the way in and back it out 2 1/2 turns out. hope this helps

Me too! I had one on my 1984 lt125. It sounded terrible when it came out. It had fallen out before i got it and they had a tube with a bolt in it and that was workin, but then it fell out. I think i got the new part though...

[John451]

Originally posted by 250exkid
ummm go on ur carburator and theres air fuel screw i had that pop out of my old 4wheeler a couple times and it bogs and makes a loude air thrushing sound... it should be on the bottom of your carb its the screw if you pipe it and jet it your suppose to put it all the way in and back it out 2 1/2 turns out. hope this helps

Me too! I had one on my 1984 lt125. It sounded terrible when it came out. It had fallen out before i got it and they had a tube with a bolt in it and that was workin, but then it fell out. I think i got the new part though...

[number52]

Ok, I think I've narrowed it down to the Reverse Speed Limiter being activated in forward gear. I've tried everything else - Believe me!

I don't know where to start because I don't have a manual for this bike. It's a 2000 Sportsman 500 4x4. There should be a page in the manual that troubleshoots this problem. I have a 2005-2006 Sportsman 800EFI manual and it troubleshoots it. But the wiring is totally different for this bike. If someone has this page in there manual, could you PLEASE scan it in and post it for me? Thanks for the help

[rundrave]

try adjusting the throttle cable, you can also take off the cover on the throttle assembly on the handle bars. there is a ETC (electronic throttle control) that has 2 metal contacts, when they touch it causes the machine to die, these are adjusted buy adjusting the throttle cable.

make sure you route the throttle cable correctly. On my 500 there is a channel along the side of the gas tank, make sure its not kinked or anything abstructing it.

My quad was acting the same way, idled great and ran great when it stayed running, but it would just randomly start acting up and i had taken the gas tank off to get to my plug, when I put everything back together I didnt route the cable right and I figured this is what caused it.

also this is a CV carb, you have to maintain a certin amount of vacuum for it to operate right. It takes resistance on the filter side of the carb to pull the slide up, not sure EXACTLY how it works but from what I can gather it has to do with velocity through the carb that pulls the vacuum to operate the slide.



also to 250ex on the comment about the honda....its a 3-wheel drive wonder, the sportsman is way better for mudding because it actually has a TRUE 4x4 system, and so what if the sportsman is a tank, more weight is better for mudding

[number52]

Originally posted by rundrave
try adjusting the throttle cable, you can also take off the cover on the throttle assembly on the handle bars. there is a ETC (electronic throttle control) that has 2 metal contacts, when they touch it causes the machine to die, these are adjusted buy adjusting the throttle cable.

make sure you route the throttle cable correctly. On my 500 there is a channel along the side of the gas tank, make sure its not kinked or anything abstructing it.

My quad was acting the same way, idled great and ran great when it stayed running, but it would just randomly start acting up and i had taken the gas tank off to get to my plug, when I put everything back together I didnt route the cable right and I figured this is what caused it.

also this is a CV carb, you have to maintain a certin amount of vacuum for it to operate right. It takes resistance on the filter side of the carb to pull the slide up, not sure EXACTLY how it works but from what I can gather it has to do with velocity through the carb that pulls the vacuum to operate the slide.



also to 250ex on the comment about the honda....its a 3-wheel drive wonder, the sportsman is way better for mudding because it actually has a TRUE 4x4 system, and so what if the sportsman is a tank, more weight is better for mudding

Thanks, but I've already replaced the slide diaphram etc. Plus, the bike runs great in reverse without the over ride button pushed in. So, this tells me that it's the throttle over ride. The bike wouldn't run at all if there was enough slack in the cable to touch these two pins together in the throttle. I tried that a long time ago.

[CSR400EX]

check to see if your ETC is bad. i know i had a trail boss that i worked on that would get about 1/2 throttle and die, i just cut the wire and it ran great after that. just cut the wire where you could splice it back together if its not it.

[number52]

Originally posted by CSR400EX
check to see if your ETC is bad. i know i had a trail boss that i worked on that would get about 1/2 throttle and die, i just cut the wire and it ran great after that. just cut the wire where you could splice it back together if its not it.

Bike doesn't die. It just cuts out like hitting the reverse limiter so it's not the ETC.

[CSR400EX]

well thats what it did, it would get to about half throttle and bog and then act like a real low rev limiter.

[number52]

Ok, I'll try that. But the wires never touch! I can see them the entire movement of the throttle. Thanks

[number52]

Problem Fixed! Exhaust cam lobe was worn. Would have checked this a long time ago, but the valves were only .002 out of spec. This was the last thing I could think of that would be wrong with it. It also started running horrible in reverse too.