high altitude jetting HELP needed!


10 replies to this topic
  • lutterfer

Posted July 02, 2009 - 04:13 AM

#1

I have an 06 yz450 and i ride in Mexico city, (the ajusco mountains) and we start riding at 9,000ft up to or very close to 12,000. Does anyone have any reccomendations on how to jet the bike? which jet sizes, clip, fuel screw, etc....???

right now the bike has a rich bog at full throttle so i installed a 160 main from 165 and fuel screw at 2 turns, the bike has a lot of torque but no top end, i also have a suzuki rmz250 and it rips compared to this one with stock pilot, 160 main and clip position #2 from top, but when i go there at about 10,500 it starts to bog at 1/4 throttle and then it runs fine, but not as much power, i know altitude has its effects, but at 7000 it runs awesome.
So my question is does anyone ride at this kind of height and what settings are you using for the YZ450???


Any help would be greatly appreciated!

  • davcon

Posted July 02, 2009 - 04:48 AM

#2

If your sea level jet is a 160, the calculations say 150 for 9000 and 145 for 12000.

  • lutterfer

Posted July 02, 2009 - 04:49 AM

#3

thanks! i will give it a try this weekend, any info on the fuel screw? i thought about 1 1/2 turns or 1 3/4

  • davcon

Posted July 02, 2009 - 05:04 AM

#4

thanks! i will give it a try this weekend, any info on the fuel screw? i thought about 1 1/2 turns or 1 3/4


Sounds like a good place to start but you'll probably have to play with the turns when you get there. Maybe someone from Colorado will chime in with specifics.

  • TC33

Posted July 02, 2009 - 06:54 AM

#5

I ride at 9-11,000 ft, 09 450 with FMF Q4 exhaust. Pipe must have leaned out the jetting, cause it runs great on the stock settings. Opps, except fuel screw is 2 turns.
It starts cold with 5-7 kicks, warm is 1-2. I was very suprised, I expected to be making some changes but it runs great, no bogging and pulls well thru the rpm range.
Stock main on the 09 is the 160. Hope this helps!

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  • grayracer513

Posted July 02, 2009 - 07:50 AM

#6

any info on the fuel screw? i thought about 1 1/2 turns or 1 3/4

http://www.thumperfa.../jetting.htm#PJ

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  • rdefonce

Posted August 04, 2009 - 08:54 AM

#7

I ride at 9-11,000 ft, 09 450 with FMF Q4 exhaust. Pipe must have leaned out the jetting, cause it runs great on the stock settings. Opps, except fuel screw is 2 turns.
It starts cold with 5-7 kicks, warm is 1-2. I was very suprised, I expected to be making some changes but it runs great, no bogging and pulls well thru the rpm range.
Stock main on the 09 is the 160. Hope this helps!

Thanks!
I will be riding at those altitudes with a '08 450F, AND I will have FMF (megabomb header) Q4 exhaust!
I figured 155 main. My bike has 165 in it. I'll get a 155 and a 160 to cover my bases. Good info on fuel screw too.
Interesting, my old '99 400F also needed a RICHER fuel screw setting at altitude to reduce popping and run better at low throttle . . .

  • TC33

Posted August 04, 2009 - 09:50 AM

#8

When I put the pipe on and took it for a ride I was very surprised how well it ran. The only problem I had was a hanging idle, which was cured with a half turn on the fuel screw. At 10,000ft+ it has way more mid range and a little more bottom than stock, no bog at all. Top end still has a pretty good hit, but is smoothed out a bit with the more mid-range, if that makes any sense. I figured I would ride it for a while and make some changes when I had problems, but have to say I am happy with it the way it is.
My bike has never backfired, not even once since I got it. I read here that some backfiring is normal, so my bike may still be a little rich. I am still running the stock header pipe.
Hope this helps!

  • rdefonce

Posted August 04, 2009 - 12:57 PM

#9

When I put the pipe on and took it for a ride I was very surprised how well it ran. The only problem I had was a hanging idle, which was cured with a half turn on the fuel screw. At 10,000ft+ it has way more mid range and a little more bottom than stock, no bog at all. Top end still has a pretty good hit, but is smoothed out a bit with the more mid-range, if that makes any sense. I figured I would ride it for a while and make some changes when I had problems, but have to say I am happy with it the way it is.
My bike has never backfired, not even once since I got it. I read here that some backfiring is normal, so my bike may still be a little rich. I am still running the stock header pipe.
Hope this helps!


Good to hear. The only diff is I have Megabomb header, which hopefully will not require jetting different jetting.

  • Wiz636

Posted August 04, 2009 - 01:58 PM

#10

All I see people talking about here are the main jets but if you guys are riding on mountain trails you won't be on the main too often, although the original poster did mention that he has lost top end power. Either way, adjusting the fuel screw at that elevation is going to do nada if the wrong pilot jet is installed. The '06 comes a little lean on the pilot from the factory but getting up to those super high elevations are still going to require a leaner pilot.

  • rdefonce

Posted August 05, 2009 - 03:55 AM

#11

All I see people talking about here are the main jets but if you guys are riding on mountain trails you won't be on the main too often, although the original poster did mention that he has lost top end power. Either way, adjusting the fuel screw at that elevation is going to do nada if the wrong pilot jet is installed. The '06 comes a little lean on the pilot from the factory but getting up to those super high elevations are still going to require a leaner pilot.


Not necessarily. My yz400f ran best at hi altitude (8k - 12k ft) with one step RICHER pilot jet than stock! Go figure . . .





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