Carb mod..air screw and washer???? - Page 2 - Polaris Riders


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Old 10-20-2003, 01:59 PM   #11 (permalink)
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This is the air screw: Mine is out 3 turns, helped alot, though I'm going to a 50 piolet tonight.
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Old 10-20-2003, 02:15 PM   #12 (permalink)
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That's a link to a server at my house. Apparently it's down. I'll have to fix that.
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Old 10-20-2003, 02:47 PM   #13 (permalink)
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polarisbob,

Yes you are right it adjusts the fuel.

So what is under the brass plug behind the mixture screw we are talking about?

CJ
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Old 10-20-2003, 02:52 PM   #14 (permalink)
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Erik, I hate to Tell you this, BUT that picture is 100% WRONG!!!!!!!!!!!!!!!

That is a fuel screw!!!!

Just to make sure we are talking about the same thing. Polaris, in their factory service manual, calls this air screw a "pilot mixture screw"!! This is what is circled in the picture!!!!!!!!!!!!!!!

It is dis-information like this that really messes up people!!

There is a reason why the mfg puts the "fuel screw" behind a brass plug/cover, and that is that most back yard tuners have no clue as to how to tune it the right way, and if tuned wrong the WHOLE carb setting is thrown off.

There is a larger issue also and that is trying to meet the government emissions requirements. But that is a whole different topic.


If the question is , Can a person get better performance by adjusting the fuel screw for "his/her" riding area and riding style?? Then the answer is YES 100% YES.

But you HAVE to have the knowledge as to what you are turning/ tuning before you start!

For your information there is NOT any "air screw" on the 2003 Polaris predator stock factory carb!!

While there are air jets that can be changed, note these air jets are fine and don't need be messed with, there is not any kind of adjustable air screw any where on the carb.!!!!!!!!!!!!!


CJ in your posts, you have posted that the screw we are talking about is both a fuel/pilot mixture screw and that it is also an air screw.

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We're talking about the pilot mixture screw right? And it's a fuel adjustment not air. It's located near the back and if you turn it out you will add more fuel. Stock is 2.5 turns out, It's where I have mine and it works great.

CJ



This post was edited by CJ on 20 Oct 03 9:26 AM . "


I am not trying to bash anyone just to make sure we are all talking about the same thing!!!


bob out!!!!!!!!
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2003 Polaris Predator / 2004 KTM 525 exc 6 speed motor.

570 Thumper Racing kit w/ 12.5 - 1 CP piston.
Head ported by Thumper Racing w/ new intake seats done by Pro-1 racing.
Stage 5 cam ( Custom design by Thumper Racing )
AC bearing mod.
Oil system mod by DJH.
KW valves ( stock size )
* #100 CDI dirt bike CDI.
42 mm FCR carb by Walt/ Fast64ranchero. ( SX carb = No TPS )
Trail Tech -10 oz flywheel. ( Stock is 30 oz/ trail tech = 21 ozs )
Mino water pump. Full flow set up, no T-stat.
PB Oil cooler.
Custom modded intake. Uni filter/ D2 moto adapter on a modded Predator intake tube.
KTM dirt bike header connected to a modded PP/ White broes muffler w/ turn down tip.
( Soon to have a KTM Bill modded CT racing full exhaust system. )
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Honda thumb throttle.
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Old 10-20-2003, 03:00 PM   #15 (permalink)
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CJ, not 100% sure, I have not taken them out, but I think they are where the MFG had to drill passages in the carb for air circuits or some such and then covered them up so that the carb will work.

It is very common to find these kind of plugs on auto carburetors, and they are just to cover passages that are machined in to them after the casting process.
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2003 Polaris Predator / 2004 KTM 525 exc 6 speed motor.

570 Thumper Racing kit w/ 12.5 - 1 CP piston.
Head ported by Thumper Racing w/ new intake seats done by Pro-1 racing.
Stage 5 cam ( Custom design by Thumper Racing )
AC bearing mod.
Oil system mod by DJH.
KW valves ( stock size )
* #100 CDI dirt bike CDI.
42 mm FCR carb by Walt/ Fast64ranchero. ( SX carb = No TPS )
Trail Tech -10 oz flywheel. ( Stock is 30 oz/ trail tech = 21 ozs )
Mino water pump. Full flow set up, no T-stat.
PB Oil cooler.
Custom modded intake. Uni filter/ D2 moto adapter on a modded Predator intake tube.
KTM dirt bike header connected to a modded PP/ White broes muffler w/ turn down tip.
( Soon to have a KTM Bill modded CT racing full exhaust system. )
Tusk Clutch kit.
Honda thumb throttle.
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Old 10-20-2003, 03:13 PM   #16 (permalink)
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Bob,

Again, your 100% right, the screw in question adjusts the fuel, no one is arguing that. Why the manual and other people call it an air mixture screw is beyond me. We're all talking about the same thing.

You really make it sound like the screw is magical...its nothing to be scared of. Your right, small adjustments is the key to making progress with tuning.

CJ
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Old 10-20-2003, 03:48 PM   #17 (permalink)
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CJ ...lol... Did not mean to make it sound magical..lol..

It's just that most people are used to tuning the air screw on their 2 strokes and a large amount of turns can be made, to a air screw, with out really hurting the performance of the bike. Where a small turn of the fuel screw will have large changes on the performance.

It is a factor of what the screw is controlling and how the air fuel ratio is affected.

With the "perfect" A/F ratio being 14:1, there are 14 parts of air to 1 part of fuel. So with the air screw you are changing the air ratio a lot less than if you are changing the fuel screw and the fuel ratio.

Small changes in the fuel screw will have large changes in the fuel to air ratio, that is all I was trying to say.
__________________
2003 Polaris Predator / 2004 KTM 525 exc 6 speed motor.

570 Thumper Racing kit w/ 12.5 - 1 CP piston.
Head ported by Thumper Racing w/ new intake seats done by Pro-1 racing.
Stage 5 cam ( Custom design by Thumper Racing )
AC bearing mod.
Oil system mod by DJH.
KW valves ( stock size )
* #100 CDI dirt bike CDI.
42 mm FCR carb by Walt/ Fast64ranchero. ( SX carb = No TPS )
Trail Tech -10 oz flywheel. ( Stock is 30 oz/ trail tech = 21 ozs )
Mino water pump. Full flow set up, no T-stat.
PB Oil cooler.
Custom modded intake. Uni filter/ D2 moto adapter on a modded Predator intake tube.
KTM dirt bike header connected to a modded PP/ White broes muffler w/ turn down tip.
( Soon to have a KTM Bill modded CT racing full exhaust system. )
Tusk Clutch kit.
Honda thumb throttle.
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Old 10-20-2003, 04:46 PM   #18 (permalink)
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so is it true that you need to drill that plug out and set it at 3 turns out when adding a clamp on filter or not? What is the stock setting?
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Old 10-20-2003, 04:48 PM   #19 (permalink)
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Start at 2.5 turns out which is the stock setting.
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Old 10-20-2003, 06:18 PM   #20 (permalink)
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Thanks for the help guys!
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