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john450f

who really knows jetting?

15 posts in this topic

Talked to my dealer about having shop mech tune/jet my bike for me because its not right and frankly I just can't figure it out. He told me before I change too much I should install a $59.00 K$N filter as it flows much more air andwould be the best place to start. I don't know does paper flow beter than clean/oiled foam? Anybody changed to K&N and what kind of results?

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Teh foam filter wil hold a lot more dirt than the paper. I have run K&N on many street bikes and like them, but would never put one on my dirt bikes. Go foam with plenty of oil to trap dirt.

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He told me before I change too much I should install a $59.00 K$N filter...

Wow. Idiot dealer alert!!

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Its safe to say that most dealers dont know squat except how to sell you a bike/parts.

You wont find better jetting tips anywhere on the planet than here!

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John,

If you havent somewhere else already, post your current bike's jetting setup, along with exhaust and any other mods you've done thus far (i.e. BK mod, etc.). Someone on here will certainly get you setup and running great in no time! I cant speak for Arizona jetting, but someone else surely can...

Larry

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Can the Main,Pilot and Starter jets be replaced without removing the carb?

03WR450FR-picked up 2/3/03. 2.1 miles and runs like crap!

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foursmoke, from the little tinkerin I've done on mine I think you can get to the main & air screw while carb is on the bike, if you loosen clamps and tilt carb slightly and have main jet wrench and short screw driver for air screw. Other jets I think more disasembly is necessary. My jetting is off but it sounds like yours is really bad, maybe you should take back to dealer for correction, just be wary if he tries to sell you an air filter. I have low end bog and it pops alot but I did some 2nd gear practice starts today and this bike is stupid fast- I could get hurt! Anyway can anybody tell us how far you have to disasemble to get this tuning done- does the carb come all the way off?

larryco, I have yz thrtle stop, baffle and snorkle removed. At about 4500 ft elevation. I think elevation is key because everybody says these bikes are lean but mine seams rich. Anybody tuning at similar elev. with advice would be greatly appreciated.

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YES, THE JETS CAN BE CAHNGED WITH OUT RMOVING THE CARB,

REMOVE THE SEAT AND TANK, PULL THE HOT START OUT OF THE TOP OF THE CARB, REMOVE THE RECTIFIER FROM THE FRAME,THIS WILL GIVE YOU ROTATING CLEARANCE. NOW LOOSEN THE CLAMPS ON BOTH SIDES OF THE CARB. YOU SHOULD NOW BE ABLE TO ROTATE IT ENOUGH (1/4 TURN) TO REMOVE THE 4 SCREWS THAT HOLD THE BOWL ON AND REPLACE THE JETS. YOU MAY NEED TO WORK THE DRAIN HOSES UP AND THEN BACK THROUGH WHEN DONE, THEY WILL BUNCH UP ON YOU A LITTLE. MAKE SURE YOU DRAIN THE CARB BEFORE YOU PULL THE BOWL. GOOD LUCK.

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MILLERTIME thanks for the heads up, I'll look at bike tomorrow and see if I can tilt carb as you describe. Till then I think I'll take your user name advise

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Why, you can get to them both without loosening the carb. Just a little steady aim, you can get either with only taking the float bowl drain off. 5 min for both :D!

Mini ratchet, 6mm socket, short flathead, calm fingers.......

Late

Dodger :D:)

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don't know what others think and by all means the 450 may be different than the 400/426, but find out what a yz450 stock setup is and run that to start with. generally it will only be a new needle, and a leaner main jet. then tweak the fuel screw. this will only be a godd baseline if you are below 4k feet elevation and you have removed the throttle stop, and restrictions in the exhaust and airbox. i think no one really knows yet whether you can run yz timing in the new 450 or not, but if you can this will only let that work even better. I know this setup has worked well on my 2000 WR400. It is almost as fast as my 2001 YZ426. Good Luck!

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Fact if there ever was one!!!

You wont find better jetting tips anywhere on the planet than here!

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Might I also take a minute to recommend having a look in your local phone book for a good SMALL motorcycle repair shop? Doing this led me to a man who knows more about bikes than I'll ever know, and the passion to do the job right every time. Oh, and I almost forgot to mention that his shop rate is about 25% less than the dealer, and he marks parts up less as well.

Cheers,

Sabooo

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