jetting ?????


9 replies to this topic
  • hamboney

Posted May 15, 2011 - 01:18 PM

#1

stock 08 450 yz,,extremly cold blooded,,runs rough till warmed up,lots of pop on deceleration,,seems lean,,,jetting ?? if so wich one and what size??,,thanks
Bill

  • grayracer513

Posted May 16, 2011 - 08:21 AM

#2

You're not going to help, are you?

What's your altitude, the ambient temperature, and what are your current pilot and main jets.

Also, has the bike been sitting unused for any length of time?

  • yz450fcranker

Posted May 16, 2011 - 11:38 AM

#3

when i got a pipe for my 09 450 the pipe company recommend stock jets for 09 160main and a bigger main jet 165 for 08 try 165 main for a start and do the rest on your own

  • dvn

Posted May 16, 2011 - 01:18 PM

#4

when i got a pipe for my 09 450 the pipe company recommend stock jets for 09 160main and a bigger main jet 165 for 08 try 165 main for a start and do the rest on your own


The main jet has nothing to do with being cold blooded or popping on decel. If you are running average temps and low elevation then your pilot jet is probably clogged. Especially if it has been sitting, as Gray eluded to. Check it and report back.

  • hamboney

Posted May 16, 2011 - 05:45 PM

#5

Bikes all stock,,Main 160 pilot 45,,low altitude,,moderate temps,,the bike has sat longer then usual but its been like this since day one,,
thanks for the input,,

B

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  • todds924

Posted May 16, 2011 - 07:24 PM

#6

Bikes all stock,,Main 160 pilot 45,,low altitude,,moderate temps,,the bike has sat longer then usual but its been like this since day one,,
thanks for the input,,

B

Run a #77 jet drill through your pilot to make SURE its really clean and the proper size.

  • curtis515s

Posted May 16, 2011 - 07:35 PM

#7

stock 08 450 yz,,extremly cold blooded,,runs rough till warmed up,lots of pop on deceleration,,seems lean,,,jetting ?? if so wich one and what size??,,thanks
Bill


I put a 48 pilot in my 08' and it helped a lot on starting and also most of the decel popping went away. You want to have a little popping on decel or you are to rich.

  • hamboney

Posted May 17, 2011 - 12:04 PM

#8

hey thanks for all the help,i think will try the larger pilot

  • grayracer513

Posted May 17, 2011 - 12:21 PM

#9

Frankly, a 45 should be big enough, IMO.

  • carver

Posted May 17, 2011 - 01:01 PM

#10

Before you go with a 48, and since it's been doing it since day one,
I'd first remove the pilot and clean it or replace it. I've now seen multiple
FCR's come with some debris in them from multiple makes. Oh look, here's one now....
Posted Image
Posted Image

This one wouldn't run right even with the pilot out 3 turns, although it's one of the worst I've seen.

If you're not comfortable with cleaning it, just replace it with a new 45 and clean the bowl.
Test that and see where you are. If not resolved, go to the next step.

Readjust the pilot screw, the setting from the factory could have been off.
First count the turns to close it (clockwise)
Then turn it back out that number +1/2. So if it was 1 1/4, set it at 1 3/4.
For ref., each 1/2 turn is approx. equal to 1/2 a pilot jet change, although the pilot jet actually
can affect mixture up to about 1/3 throttle where the pilot screw is done at around 1/4 throttle.
My guess is that a new 45 with readjusting the pilot screw will solve it.

If you have to go a full additional turn out on the pilot screw to get it to run right,
you're better off going back to the original pilot screw setting and going up one on the pilot jet.

Edited by carver, May 17, 2011 - 01:41 PM.






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