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mikuni flatslide tuning

4979 Views 13 Replies 6 Participants Last post by  vmaxyam, 
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my 99 xc xp 500 (non-ves) runs a little fat for my taste, and i'm looking to drop the jet needle one notch (raise the e-clip one position). is this safe to do? it is jetted correctly for my elevation and temp, i'm just looking for crisper throttle response and a little better mpg.
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B
Should be safe enough but the best way to check of course would be to grab fresh plugs after you make the change then once you've got a few hot miles on it then pull them right there on the trail as soon as you stop and see if they are still burning clean. Any chance you've got EGT probes too? That's really helpful for fine tuning.

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I think.... therefore I sled
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Two '94 Indy XLT SKS
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X
you psychic or somethin bman? haha, i just bought new plugs about a half hour ago. i'm gonna work on it tonight, so i'll try your method to see how it works. and nope, ain't got no egt probes.
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B
I'm .... 'or something' closer to psycho I think.


One of my sleds came with triple probes so I was lucky. Don't run it too long like that if you are concerned and can't check the new plugs right away though. It's a tough and expensive gamble if you come up snakes eyes.

Good luck.

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I think.... therefore I sled
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Two '94 Indy XLT SKS
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X
haha, too true bman. i'm not sure if i'll mess with it tonight, or wait until i have some more time to really fine tune my setup. would my warrenty cover that anyway? haha
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S
raising the clip won't give you much noticeable mpg change since it controls from 1/4 to 3/4. 1 clip position should be safe. What is your elev. and temp?? Crisper throttle is achieved with air screw and pilot jet adjustments.
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X
elevation is around sea level, and temp is usually -30 to 40. varies quite a bit. i don't know anything about the air screw and pilot jet adjustments. any info on that would be appreciated.
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S
start with air screw. located right side, near air box. use flatside screwdriver all way in until lightly seated. Remember how many turns you did (they should be the same for both). Then set both to 1 turn less than when you started. Take for a spin. Will adjust off idle pick up. If don't like it go out to 1 past original. REMEMBER Turn in=lean, out=richer. Tell me if this doesn't work. Then need to change pilots jets.
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Polaris-Man
Ahem, turning it in won't lean it out.

Turning it out will, when u screw it in, it closes off the air, therefore causing more fuel to go in. When u turn it out, it opens it up allowing more air in therefore leaning it out.


http://www.bolliger-mabillard.com

I Love B&M Coasters.
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thanks for the info guys. i didn't adjust it tonight for fear of messing something up and ruining tomorrow (er today's) ride. i'll probably try to tune it a little later. i put the new plugs in and the old ones showed it is running a little rich.
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S
Page 118 Clymer manual and I quote " a. Turning the pilot air screw clockwise leans the fuel mixture. b. Turning the pilot air screw counterclockwise richens the fuel mixture." xc racer do you have the owners manual to clear this up once and for all?
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yeah, i have the manual, but it doesn't say how to adjust the carbs. i suppose the factory doesn't want you messing with it too much and blowin em up- warrenty.
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Z
polaris man is right. air screw controls air,hence if you turn screw in it closes off air passage and runs richer and vice-versa. if they are fuel mix screws (on engine side of carb) they will do it the opposite in will lean out because it closes down fuel passage.
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V
On the newer style mukuni's ie. 96 and newer yamahas they do not have an air screw they have a fuel enrichment screw which is located under the float bowl. By turning this in it leans the the fuel going into to carbs at low throttle.turning out is opposite richer. there is an air inlet jet on the front side of the carb bottom hole on right i believe i would have to pull them to make sure though. If you go to a larger diameter hole this would also lean out your mixture .If there is infact an actual air mixture the above two reponses are correct.

Ride hard but safe. Vmaxyam
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