Confused. Someone please enlighten me.

[YZrider250]

I've been messing around with the jetting on my YZ250 for a while now. Right now my pilot is a 48, and my main is a 175 with the needle clipped two slots from the top (Thats how it was stock). My main and pilot are both one size down from what they came stock. I got a new plug, and tested to see if it was running lean or rich with these settings, and the first time I did it, my insulator was a brown color. I tested it again tonight, and the insulator was white again. The only thing I did different when riding the bike this time was I opened it up more. Heres a pic of a my plug (I'm sorry its big and blurry):

My manual shows that as being normal, but everywhere I read, perfect is that mocha brown color and lean is white. Which one is it, and does my plug actually look good or lean? I'm confused, and getting frusturated. This is the first time I tried jetting a bike, and so far its only left me wondering. Hopefully I'll get better.

 

[YZrider250]

Anybody?

 

[XRpredator]

you never mentioned how the bike ran . . .

 

[ChR1s]

That's white alright. Seems it was running lean while on the main jet more? I'd go back to the stock main, then mess with the needle clip position if necessary.

The pilot jet is only going to effect about the first 1/8 of throttle -- just off idle. If adjusting the pilot screw isn't effective within 2 turns out, downsize. If it isn't effective at all, upsize. I think that's how it goes? Hey, it's been a while. ;)

The main will have a significant effect starting at about half throttle. It's easiest to test the main by getting the engine warm, swap in a new plug, then go for a WFO rip -- pull the clutch in & hold the kill button in, then stop and check the plug.

Once the pilot & main are set, you can tweak the needle clip for best "feel" -- the bike should not stumble (rich) or feel like it's gasping for air (lean) when rolling the throttle open.

My '06 is stock and runs well (idles, pulls cleanly) at a few hundred feet above sea level. This time around (I had an '02 prior to my '06) I've started running Bel-Ray H1R instead of Yamalube 2R. The Bel-Ray seems to be burning better at lower revs/temps (woods riding). I always run 32:1.

 

[oldfrt613]

Yamaha has some of the best stock jetting out there, any particular reason your messing with it ? Do you feel its not running right ? The only change we made on the '05 was to drop the pilot one size - but we run race gas, 32:1.

 

[Rich Rohrich]

Read this : Plug reading 101 http://dirtrider.net/forums3/showthread.php?t=92818

 

[YZrider250]

Thanks for the replies guys. I will go up on main size and see how that does.

Before I started messing with my jetting, the bike seemed to run rich. When I first got it, it ran perfect. Temperatures were maybe in the mid 50's then. Now that we're going on summer, the temp has gone up about 40 degrees, and pretty soon here its going to be pushing a 50 degree difference. I think thats why it started to show signs of running rich.

 

[Chili]

Before you touch anything based on what your seeing in that photo I'd suggest you read the thread Rich linked for you.

 

[YZrider250]

I didn't read all 8 pages of that thread, but I read enough to now know there is no way to tell how the jetting is by looking at the nose of the plug.

About the mixture ring. I know you look at the base of the insulator for it. What do I look for in that ring? Do I look at the color, or how big around it is?