Pilot jet too large?

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Jul 6, 2004
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#1
I have a 2003 with a woods pipe, stock silencer, vforce 3, and snorkel removed. I have jetted to where I thought it ran perfect until I went on a ride with a couple friends. After hours of just off of idle and very slow speeds my bike loaded up and began to fowl the plug. I got out on the road and it cleared out. I decided it is a little rich so I turned the air screw out another 1/4 turn (now at 2 turns out) I keep reading that a 38 is probably as small as I should go but it now seems that a 35 pilot is in order. The 148 main jet checks perfect if not a tad rich on the plug. starting at 4500 feet mnimum. usualy take off at 5500 and up. what do you all think?
 

dirt bike dave

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#2
How old was the plug? Are you running a 9 or an 8 plug?

They don't last forever, so an old plug could have contributed to the fouling/loading up. If it was a new plug, I'd probably start with the aircsrew at your new position of 2 out (I guess you were 1 3/4 when the plug loaded up).

If hours of constant idling and low rpm at high altitude is not your normal riding condition, I would not jet to optimize the bike for that situation.

If it was otherwise running great besides loading the plug up after hours of just off idle, you can't be far off.

Personally, I think it is nice to have a little safety margin, especially if you go on long rides where weather and riding conditions may change alot during the day. For example, if you jet it to run perfectly crisp for low rpm rock crawling at 6,000+' elevation, 80* temps at noon, are you going to be too lean when you leave camp back at 8:00 am, 4,000' elevation and 55* temps?

It's always a compromise, so it's best to err on the side of more fuel. Sounds like you are in the ball park now. If it were me, I would put in a new '8' plug and leave the airscrew at 2 out, then go for a ride.
 
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Dec 29, 2002
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#3
I ran a 35 at 6000-11,000' elevation. When I went down to 4000', it was usually hotter and that balanced things out. Anytime you're riding a 2S at low RPM's, you need to pull the clutch in and rev it a bit from time to time.
 
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#4
you say you ran a 35. what main jet were you running? just thinking most of us end up almost matching mains with certain pilots on similar set up bikes. I do run br8es plugs and just put a new one in. I just got back from a couple of tanks worth of riding at a bout 6000ft. temps were between 70 and low 90s. I think it felt as it may even still be a size too large on the main(ran it hard shut it off and put it on the trailer) havent pulled the plug yet. It still runs so much better than before. I know this is no indication of jetting but same fuel and oil and it sure smokes alot less.