05 yfz 450...jetting issues

[crprestridge]

just moved from sea level to about 4500 feet above see level. I already have a #170 jet in my carb...i finally got it to start after turning the fuel/air mixture screw a total of 5 1/2 turns out(it was running good at 2 turns out). gonna get a new jet and here's my question.....what size should i go up to? i'm trying to avoid buying a handful of different jets. and my next question is do you think i'll have to change my pilot?

[DirtDemon]

You need to go down in size, not up. I would aquire all sizes from 160 to 170, you need to be able to adjust for temp changes. I would start at 165 and go from there. If you had to turn your screw out 5 1/2 turns just to get it to start, then your pilot jet is too rich. You will need to run a leaner pilot too. The engine should idle highest at 1 1/2 - 2 1/2 turns out, use a pilot that gives you that result. You will probably also want to move the needle clip up one spot. If you have to run it with the clip in the top spot, then you might try a needle with a leaner taper.

Edited May 29, 2010 by DirtDemon

[dirtjunkie85]

I agree you may want to go down in size to get it to run better I would also recommend checking out this link they sale individual jets so its a lot cheaper then buying a entire jet kit they also have great techs that may be able to help.

ATV jets

[Stoopidbot1]

For every 1000ft you go up in elevation, drop one size on the main. If your quad was dialed in at sea level then the main is the only thing you need to change.

[DirtDemon]

If he had to turn the pilot screw out 5 turns to get it to start, either the pilot is too rich, or there is something else wrong.

[crprestridge]

ok. i now have the pilot at 42(one size smaller), the needle is on the middle clip, and the main jet is 160(from 170). It idles fine and mid throttle is good. It still cuts out on topend(acts like water is in the gas, which i know is not the case). Do you think i still need smaller main? The bike ran crazy fast at sealevel with no trouble. i haven't adjusted the needle at all. What to do?

[crprestridge]

i think i got it dialed in now.....needle in the middle, pilot jet at 42, and main at 68. running good.

[DrtyGrlKristin]

i think i got it dialed in now.....needle in the middle, pilot jet at 42, and main at 68. running good.

:biggrin: Yay! Glad to hear it....

[DirtDemon]

Good to hear, I am suprised that a 168 main is doing it, but moving the needle may have helped. Also if it is alot colder there, the elevation will make less difference because the cold air has more oxygen in it, helps offset the high altitude. Either way, glad to hear you got it dialed in.

[crprestridge]

i didn't move the needle at all actually. i was just posting all settings in case anyone had the same circumstances in the future. all i did in the end was get some advice from local yamaha mechanic and went down one size (from my origianl sea level setup)for the pilot from 45 to 42 and one size for the main from 170 to 168. i had the main as low as 162 and on top it would get real lean and cut out bad. it's all good now though. thanks everybody for your imput. you guys are awesome and so very helpful. if ever in the ogden/ salt lake area, hit me up. i would love to ride with you guys. later. thanks again.