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REJETTING RIGHT NOW AND MY DEALER SAYS HE HAS NO JETS FOR THE YFZ BUT HAS PLENTY OF JETS FOR THE YZ 450, WILL THESE WORK IS IT THE SAME CARB.

I'M INSTALLING MY PRO FLOW KIT TODAY TOOK THE BAFFLE OUT AND I'M PLANNING ON JETTING 168 MAIN 45 PILOT STOCK NEEDLE ON 5TH CLIP DOES THIS SOUND ABOUT RIGHT.
 

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with the K&N filter or foam filter? if K&N you may need to go a little richer than that. and yes the YZ450 jets will work the same as long as you are talking pilot and mains only. the pilot air jets are different on the bike. Not different thread or anythin but different amount of flow.
 

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That will work or a 170 main with the foam filter and lid off. If a K&N you can go a 175 main no problem with the stock needle on the fifth and the lid off, you will have to play with the air screw to get it right. (running very very well). The 45 pilot also is a good choice. All Keihin jets are the same they are used on many different bikes.
 

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It's not that it's too lean. You will just have more top end power with a little larger main jet. With a 168 you can leave the airbox lid on. Tuning an engine is all about balance. When ever you increase the air flow you increase the fuel so there is something to burn. The things required for fire or combustion which creates an engines power are HEAT which is the spark, Oxygen which is the fresh air sucked in and fuel which in this case is gasoline. more air less fuel = lean, more fuel less air = rich the balance of the two is tuning. The pilot adjusts your bottom end the main is your top end and the clip on the needle is your mid which is kind a balance of the two. Take it in steps. What I find that works well is first of all everything stock (45 pilot 165 main stock needle untouched) lid on. High flow exhaust or baffle removed ( 45 pilot and 168-170 main needle untouched) lid off. High flowing exhaust W/K&n lid off (45 pilot 175 main needle on 5th or 6th) lots of power. High flow exhaust with cam mod, K&N intake (45 - 48 pilot 180 main with 6 on the clip) I did not see a big difference on the bottom between the two pilots it all depends how well you work the air screw on bottom of the carb. The 45 had a little more of a snap off the go which works well if I short shift into second which I usually do. The 48 works well If you want everything out of first but did bring my front end up a little to easy in the sand. Every thing works different for every one. It is a little frustrating but take some time and play with it, get to know your bike.
 

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Originally posted by RESCUE YFZ@Nov 10 2003, 11:42 PM
SO A 168 IS TOO LEAN IF I HAVE THE K&N FILTER???
yeah I would say a 168 main with a K&N and no-lid at sea level is too lean. I am running the stock foamy still with a 168 and it is perfect.
Isaac
 
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