First of all I want to commend you folks on such a great site.
We are working on my friends 01 Polaris 335 Trailboss He has owned about 4-5 months and has some accelleration problems and has been this way since he got it. Here is what we have done and checked so far, new spark plug, spark plug cap, air filter, checked compression(150PSI), Checked valve adjustment(Perfect) and cleaned the carb. Now here's where it gets goofy, he said that it has done this since he has owned it, when you ride it it seems like it runs pretty decent up to about half throttle but not as responsive as it should be. After about half throttle it doesn't seem to make any more power and kinda misses a little but it seems like it wants to go but just can't. Now, with it idleing in neutral and the air box lid off you can rev it and at about half throttle it starts making little pops back thru the carb, you take it to wide open and it gets worse and you can pull the choke out all the way and it starts trying to rev like it should. Now if you are riding it wide open throttle and it is missing and you pull the choke out it doesn't make any change, just keeps acting like its trying to make power and go faster but just can't do it. I would think that reving it in neutral and pulling the choke(Making it richer)and it trys to run right it would do the same while rideing it and pulling the choke(Making it richer)would make it run better but it doesn't.

What am I missing here? We have a ride here in the next few days and need this thing fixed. Any and all help on this problem would be greatly appreciated.

Sorry for such a long post but just wanted to make all the symptoms known.

Please help, Caanan

 

You said your friend has only owned this quad for 4-5 months but its an 01. Could this ATV have been improperly jetted before your friend bought it? From what you have explained it sounds like a carburator problem.

 

Sounds like jetting to me also. Mine did it when I put my RCR kit in until I got the jetting right. Any mods that you know of done to it?

 

Thanks for the replies, I've Was thinking the same thing(Jetting) but this machine is bone stock right down to the air filter(it's been replaced of course). when I was taking the gas tank off and disassembling the carb I payed close attention to everything like the bowl and diaphram screws and the jets and they looked like they had never been touched with a screwdriver or any tools. Does anyone know how much fuel pressure the fuel pump on these machines are supposed to put out? I've been an ASE certified automotive Master technician for 25+ years and have worked on every thing from ATV's to Komatsus but this one really has me scratching my head.

Any other ideas?

Thanks again, Caanan

 

Just in case you tear into the carb again, the jets should be:
Main #145
Pilot #50
Air #175

 

Thanks scooter, I am getting ready to do that just to make sure I didn't miss something. You wouldn't happen to know what the fuel pump pressure should be do you?


Thanks again, Caanan

 

Couldn't find anything for that model, but I did find a 47mm carb for a 400 (with 414 kit) for drag racing needed 4-5 psi on it's fuel pump, so it shouldn't be more than that.

 

Ok now everyone has put input about the jetting.Try unplugging the rev limiter.It is the black box with 3 wires and one is black.Unplug the black wire and see how it does.If this doesnt help take the secondary clutch off and check the buttons.

 

Hello ftwflh, would a problem in the secondary clutch keep it from reving past half throttle even in neutral and then try to start reving when you pull the choke all the way out? I am not doubting you just curious.

Thanks, Caanan

 

Ok.....I disconnected the black wire from what I am assuming is the rev limiter(Small flat black box on right side of the frame under the headlight assembly with three wires), It did not change anything. While I was at it I took the air filter off and ran it up to about half throttle and it was popping back thru the carb so I went to wide open throttle and it really started popping and i put my hand over the air box where the air filter goes and regulated the air intake and it cleared right up but as soon as I removed my hand it went right back to spitting and sputtering.

Caanan