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post #1 of (permalink) Old 11-04-1999, 09:11 PM
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700 polaris lean condition mid range

I have a 98 700 crank shop porting, twin pipes, v-force, and union bay 12.5:1 heads between 5000 and 6000 rpm I run extremely lean I have tried den,ccl,1368,1370,1371 needles And have not been able to get rid of it any help would be apreiciated. Also if anyone has tried different carb what was your results thanks

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post #2 of (permalink) Old 11-06-1999, 06:25 AM
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Re: 700 polaris lean condition mid range

Thought I'd throw this out, might help. Aaen's Carb Tuning Handbook mentions the
occurance of lean burndown problems caused by vibation's effect on the inlet needle. He talks about a "natural critical torsional frequency" that can occur above the factory designed operation speed on modified engines, so it may not apply to your midrange condition. I've also read of possible problems with fuel foaming in the bowl due to vibration, which can include air in the fuel and cause a lean condition. That's why they have the little plastic thingy that pushes over the main jet on a lot of carbs. Aaen has the following reccomendations for curing vibration problems: long and soft rubber carb flange, or a heavier flywheel. Something more to think about.
Pete

post #3 of (permalink) Old 12-04-1999, 07:02 PM
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Re: 700 polaris lean condition mid range

I have a '99 700 RMK w/the works (case porting, cylinder porting, SLP pipes, Union Bay head, reeds, bored carbs, etc).
I ran into the same problem you have when I installed my boost bottle. I went from 42 pilot jets to 48s (alt compensator REMOVED).
I am assuming you removed the alt compensator when you starting mod'ing the motor. If you haven't, yank it, it's causing part
of your problem. Once you have removed the ACCS and capped off the ports, install size 42 pilot jets and put the clip in #2 position.
If you're running a boost bottle, you should probably be running about a 48 or 50 pilot jet. If bigger pilot jets don't solve your problem,
you're probably sucking air from somewhere around the carbs. My carbs have been bored to 41mm (which doesn't affect setup as much
as one would think) and I run a size 48 pilot jet, clips in #4 (rich), air screw 1 1/2 turns, and 175/178 mains which runs at 1300 degrees
WOT at 7800 feet. Hope this helps, keihen carbs and porting work awesome together, but they can be real bitch to get dialed in
sometimes.........FullMod.


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post #4 of (permalink) Old 12-07-1999, 08:26 PM
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Re: 700 polaris lean condition mid range

The jet needle is the most effective component in the 1/4 to 3/4 throttle range. The straight diameter (68, 70, 71) part of the needle size only affects the transition from 1/8 to 1/4 throttle.

If your rich at 1/4 and lean at 3/4 throttle, you need a needle with a larger taper. The taper is represented by the first two digits in an OEM part number. ie. 1368G represents the stock 13 = taper of 1.34, 68 = 2.685" and G = 39.95 Valid taper numbers are 11, 13, 14, 20, 22, 30. The R at the beginning of the number jest specifies that it is an OEM needle.

You can obtain the Keihin product catelog for free by calling them and asking for it. It gives you all of the carb specs and tuning info.

Hope this helps.
Mark

Mark
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post #5 of (permalink) Old 12-07-1999, 10:34 PM
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Re: 700 polaris lean condition mid range

Thanks for the info Fullmod, and powderbound
Do you have a number for Keihin or where they are located I would like a copy of that Info? Since I first posted I have had some time to play with the sled this is what I come up with: timing at 15 deg at 8000 rpm, running straight AV gas, I have 6 slides 200/205 mains, CCL needles in #2, and boost bottle removed (it is sent back to SLP for a new one), 35 pilots. With boost bottle I ran 50 pilots. It does run better with the boost bottle. Even with the 35 pilots it is rich at idle. Between 5000-6000 rpm 1200 deg on race pack 6000-7000 1250 deg and wide open 1275 deg. this was all tested at 2000 feet and about 6 inches of snow in a field. I do ride mountains mainly so there will be a little more tuning. when I get the boost bottle back I will try it and will post my results

post #6 of (permalink) Old 12-07-1999, 11:17 PM
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Re: 700 polaris lean condition mid range

Keihin's number is (262)860-6000 http://www.keihin.com

Cycle Works is a distributor for their snowmobile line at 1-800-661-9653

The idle mixture screw controls the amount of air to the idle and slow circuit. out = rich, in is lean.

Off idle to 1/4 throttle is controlled by the slow (pilot) jet and slow air jet. lean = smaller slow jet and larger air jet.

I actually learned something by reading a manufacturers product catelog. I wish that this was all available on the web though.

Mark
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post #7 of (permalink) Old 12-08-1999, 12:16 AM
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Re: 700 polaris lean condition mid range

Mark, just a note that some of the info you are giving is a little off. The numbers that you gave as examples are polaris numbers as you know. The G in the polaris does not cross with the G in the keihin parts. The cross from the polaris G is an E which is 38.15 in the L1 (length). The cross from the polaris 1368G is a KEHCEJ. The R in the polaris part means aluminum construction, the keihin ones are brass. The PWK carbs have an air screw - out is lean, in is rich! They do not have an air jet.

post #8 of (permalink) Old 12-08-1999, 07:13 AM
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Re: 700 polaris lean condition mid range

Keihen's specs must be off a little as I was quoting from their specs in the back of their carb book. The R in the OEM number actually = Kiehin part number N427-48??? I do not not know if that represents aluminum or not but since it is I would not try to dispute it. Keihin gives no cross reference for the G so I assumed it was a direct conversion. Thanks for the info.
Is there another source that gives more acqurate information than Keihin? I would like to have it if you know of a source. I would like to find more direct reference material as well if you know of any out there. ( shocks, cylendars, heads, tracks .......)

Mark
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post #9 of (permalink) Old 12-08-1999, 10:54 AM
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Re: 700 polaris lean condition mid range

I do not have the book you have so I really don't know what is in there, like the N427-48? I have a some polaris high performance manuals that I get the info out of. If you don't have one you should get, tons of info in them including the carbs adjustments and a needle explanation. Thats where they say R means aluminum construction.

However it does not have the keihin needles themselves listed. For this I got a local aftermarket supplier's listing and explanation. To check that I had the right cross from polaris parts to keihin I measured the needles with a digital caliper. Once I had the stock 1368G to KEHCEJ cross confirmed I then can pick the needles I want by size relating to stock. All the info I gave comes from these two books and was verified by me with a caliper. I have done lots of tuning (forced too) on these carbs the last couple years getting my sleds to run correct. Once I learned the keihin numbers (used to mikuni rounds) it was no big deal. No bogs, stumbling, pops, lean or rich spots and the mileage was greatly increased not to mention a few hp. This was on stock sleds, flatland style. These carbs can run great for me but FUSSY as to the air screw settings. Fortuatly once the main calibrations are done, unless there is a big temp change, a quick air screw adj does it.
But I probably told you everything you know already. If you need a part number for a HPerf manual or anything else let me know.

post #10 of (permalink) Old 12-11-1999, 10:50 PM
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Re: 700 polaris lean condition mid range

minus40 I would be interested in part number for performance manual thanks

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