Fuel Screw and Altitude


3 replies to this topic
  • ETP

Posted June 10, 2007 - 03:21 PM

#1

I finally got around to installing a Zip Ty fuel screw and #50 pilot jet on my Canadian model 03 WR450. I'll post my info on the jetting database once I get the bike out for a few hours of riding.
Right now at 1 3/4 turns out on the fuel screw, the throttle response is much better and starting is easier. (1500ft) :thumbsup:
My question is: which direction do I adjust the fuel screw when I go to higher altitudes?
I realize that I will only get some improvement without changing the jets for altitude. Used the search engine, but couldn't find the specific info on which direction. In or out?

Thanks.

  • WR_Dave

Posted June 10, 2007 - 07:36 PM

#2

Higher and hotter -- screw in (less fuel-leaner due to the air is less dense)
Lower and cooler -- screw out (more fuel-richer due to denser air )

WR Dave.

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  • ETP

Posted June 11, 2007 - 08:29 AM

#3

Higher and hotter -- screw in (less fuel-leaner due to the air is less dense)
Lower and cooler -- screw out (more fuel-richer due to denser air )

WR Dave.


Thanks for the input.
In a few weeks I'll be up in the mountains at around 7000ft. and will turn the fuel screw inwards 1/4 turn at a time (If needed) and see what happens.

  • WR_Dave

Posted June 11, 2007 - 09:14 AM

#4

If you are going to that altitude you will need to drop your pilot size a few #'s as well as your Main jet size. I run in those altitudes quite a bit and am using a 40 pilot and a 165 main with the YZ needle on the 3rd clip position. WR Dave




 
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