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Old 12-04-2008, 08:03 AM   #1 (permalink)
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Pilot jet or air screw?

I have a 99 or 00 500 indy classic that i just changed the main jets down to 340. From a dead take off it's slow to start until you get up to about 15 -20 mph/4500 rpm. After that it's gone. Any thoughts from anyone on what i need to change
stock pilot jet is a 40 -
ambient air temp is -5 to +20 (340 mains)
TIA All!
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Old 12-04-2008, 01:25 PM   #2 (permalink)
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What are your air screws set at? Try one turn out from lightly seated. Then if it still bogs, go in 1/8 of a turn on both air screws, retest. If you bottom the air screws with no improvement, you may need larger pilot jets or the air or fuel passages to the pilot jets are clogged.

You should also ensure that the belt is good, and belt deflection is set properly. There should be about 1/8" of belt riding outside of the secondary clutch.

If it was running good before you changed the jets, I'm betting it's a carb issue...
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Old 12-04-2008, 02:13 PM   #3 (permalink)
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Hey Dan,
Both are set at factory - which i believe is one out. Everything was mint when i took it all apart to install the new mains. Do we or anyone know what the adjustments are for air temp?
Thanks
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Old 12-04-2008, 03:03 PM   #4 (permalink)
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From idle to about 1/4 throttle, the mains aren't giving you much fuel. The air/fuel mix comes from the pilot jet, which you didn't replace.

Try adjusting in on the air screws, it won't hurt the motor to go richer. I have had some sleds that required 1/2 turn out to make them run right from idle.

There really isn't an adjustment on the pilot jet for air/temp. It's not something you usually have to worry about. Where is the e-clip set on the jet needle? You could try moving the clip down a notch to richen the mid-range.

Don't forget the belt deflection too. If your belt is riding too far down in the secondary, the sled will act like your car does when you take off in too high a gear...
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Old 12-04-2008, 04:49 PM   #5 (permalink)
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The belt looks (as i remember) like it seats about an inch and a half down from the outside edge of the clutch...then again i cold be totally wrong.

The clip is set at factory... i think it was 2nd from top.

I know it's running rich at idle cause it sits there blowing smoke if it sits idling more than a minute. I fouled 1 of my brand new Iridiums letting it idle to warm up for about 10 minutes.
Where does mid range start? Do I look at total rpms and go off that?
Thanks dan
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Old 12-04-2008, 06:48 PM   #6 (permalink)
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If it really is an inch and one half down, that would roughly be the equivalent of trying to drive a car starting in 3rd. Will eventually wind up, but takes a while. Check for proper belt size, and clutch operation ( sheaves snapping shut). Ideally, belt should ride about 1/8" high out of the clutch.
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Old 12-04-2008, 06:53 PM   #7 (permalink)
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If the belt is down inside the secondary clutch at all, your deflection is not correct. It should be riding just outside the clutch, to flush with the clutch. You may have a secondary spring problem, which will require disassembly and replacement of the spring. You can try to adjust the deflection with the adjuster on the outside of the clutch. Loosen the screws, rotate the adjuster until the belt is flush.

Can you take a pic and post of the clutch? If it's down that far, that will make it very hard to get going. Think of the clutches as gears; when you start out, there is a small gear (front clutch with the belt down at the bottom) driving a large gear (rear clutch with the belt at the top). The smaller the front gear and the larger the rear gear, the greater the torque multiplication. If you are starting with the belt down in the secondary, it's like a small gear driving a medium gear; not near as much torque multiplication. It's like taking off in third in a 5 speed; You can slip the clutch and eventually get going, but it sure takes a long time. After you reach the normal speed for that "ratio" things will run normally.

edited: that's what drolds said, while was running off at the mouth, so to speak
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Old 12-04-2008, 06:59 PM   #8 (permalink)
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Checking the clutch or taking a picture isn't really an option - the sled is about 200 miles away in the garage up north. I could be TOTALLY wrong - i've never looked at it while i was moving or while it was engaged. I'm realistically thinking it's jetting - i changed out the mains and the top end is great now. The people i bought it from used to take it to the UP (Michigan) where it's a lot colder so it was probably fine then.
I'll check the clutching and jetting next week when i'm up.
THanks all
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Old 12-04-2008, 07:01 PM   #9 (permalink)
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Regarding the air screws.... do either of you know what the stock settings are?
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Old 12-04-2008, 07:06 PM   #10 (permalink)
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You did a much better job of explaining!** I like to think of the clutches acting like the front and rear gears of a 10* speed.** I was amazed at what a difference it made bringing the belt from an 1/8 down to 1/8 out of the sheaves made on my old 97 500.** I guess you don't notice the belt's gradual wear until you fix it.

As far as the air screws, there might be a sticker under the hood that says so, otherwise IDK off the top of my head. Dealer would tell you for sure though.

Last edited by drolds; 12-04-2008 at 07:08 PM. Reason: ..
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Old 12-04-2008, 07:52 PM   #11 (permalink)
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I'll double check - and now that i'm thinking about it - the belt may have been sitting about a 1/4 inch down
as far as dealers go - they only seem to know as much as i tell them...which isn't much... IE i already asked them - good advice under the hood though -thanks.
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Old 12-04-2008, 08:28 PM   #12 (permalink)
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I adjust the air screws one turn out from lightly seated. Then at idle, I adjust each screw to obtain fastest idle, that is usually right around 1 turn. Then I set the idle to the RPM I want. Polaris standard for round-slide Mikunis is 1 turn out (1 to 1 1/2 in some books) but you can go as many as 3 out and as little as 1/4 turn out to get proper functioning.
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Old 12-04-2008, 08:40 PM   #13 (permalink)
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that's for both the air screw and the pilot screw too right dan?
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