Jetting advise

3 replies to this topic
  • slomo138

Posted March 23, 2003 - 06:10 PM


I put on my new Thunder Alley pipe saturday.While I was at it decided to drill some holes in the air box.Have a yz450 needle on order but it has not arrived yet.So I changed the main to what was sugjested by TA. a 170 he said to leave pilot alone,I'm using a 48,dropped clip to number 5 pos..Started bike would not run without choke.Right now I have had to go all the way up to a 65 pilot to get it to idle and run pretty good.
This is my first 4 stroke so I'm new to jetting them.
Are that big of jet changes common ?
Would the YZ450 needle kept me from making such a big pilot jet change ?
Is anybody else using a TA and opened up airbox? and if so what jets are working out for you?

  • Indy_WR450

Posted March 24, 2003 - 06:40 PM


Hi Slomo138,
You are doing things right the way I see it. The stock jetting is directly from page 1396 of the EPA manual on off road vehicles. The idea is to piss of the new vehicle consumer and frustrate them to the point where they do not want to go off roading ever again. That is if they can ever get the bike started. But seriously, my jetting below works well with the stock pipe and baha baffle insert. I just ordered the TA pipe from Bob and will be dealing with your same issues then. Stay in touch on this. I will send you a PM with a reminder when I get my pipe.

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  • WR450

Posted March 24, 2003 - 09:26 PM


Hi I have a Thunder Alley and I am using a 165 main and 48 pilot
My bike is Euro spec and has a richer needle and jetting to US

You can compare your settings to US in the Manual my jetting is stock Euro with a 165 Main for the Thunder Alley
I am at sea level

The needle will not affect your idling

I think there is something else wrong to need such a big pilot

  • slomo138

Posted March 26, 2003 - 06:39 AM


What else do you think could be wrong ?
Could it possibly be a plugged up pilot circuit ?
Bike runs great on top.


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