I just bought a Pro Circuit T4 slip on with a K&N air filter in the airbox with the lid on. I'm at about 900feet and its about 32degrees. If anything these mods should make my bomber run lean, right? Well I am fouling plugs, they are black and the spark arrester screen is black with carbon. I haven't touched the needle or the main jet. Pro Circuit's directions don't say to. What am I doing wrong. Please help me so I can go riding Saturday.

 

Try taking the air box lid off?

 

jeffnrivercity, Good idea! Crashnburn, you didn't say "how your machine was running" Is it revving all the way out evenly when you blip the throttle? Any flat spots? Idling ok? You might try raising the needle one clip position and/or going up one main jet size all with lid off. Just some thoughts....

 

I haven't been able to give it a good run. I let it idle for about a minute and checked the plugs(new)and they were black and wet. Is it possible that my wheeler was set too rich from the dealer? I only have about five hours on my Baja and this is my third set of plugs. I keep fouling them out, even before the pipe. Do I need to lean it out?

 

After a pipe and filter,you should be going to richer jetting [img]i/expressions/face-icon-small-confused.gif[/img]
Try running it hard for a while and dont let it idle to long after your run(check plugs or a plug),this will give a better reading for your main jet.If your idle mixture or pilot jet is too rich this could be why your plugs look black after a period of idling.
Jeff

 

I realize that I should have to richen it but when the plugs are black doesn't that mean its already too rich. Sorry I just don't get this jetting. On my last wheeler I paid to have the dealer do it. Maybe I should bite the bullet and let them do it$$$

 

crashnburn...If you want to learn a little more about tuning mikuni carbs, let me know. I have the complete Mikuni tunning manual/parts.
It's tunning for Mikuni carbs on HD bikes, but the theory is the same. I don't like to see someone pay for something that they can do.

jeffnrivercity's lid off idea would be my first choice. buttfungus is correct too, run it!

If you think it's the pilot, I would increase the idle speed to 1000-1500rpm, let the engine warm up, turn the air/idle mix screw (back, lower, left side) "in" until the idle speed changes, then "out" until the idle changes, set the screw half way between the two, return to your normal idle, turn off the engine, count the # of turns "in" on the screw until is bottoms "lightly". You should be between 1.5 & 2.5 turns. This info is from the Mikuni manual.

 

There is a good possability that you have a float set too high or your choke is not pushed all the way down. On my bomb the choke has two clicks (detents), the first one is easy to overcome but the second can be difficult at times and I have had the same results when I thaught it was pushed all the way down when it wasn't. Sometimes its so hard to push I think its going to break.

 

For all Mikuni carb users, here is the site that has the tuning procedure:

http://www.mikuni.com/

It's for HD bikes, but it should still work.[img]i/expressions/face-icon-small-cool.gif[/img]

 

Crashnburn,
All of the tips you've been givin are good, but based on your description of the problem your problem isn't with jetting it is with the idle mixture screw setting. At idle, especially at 32 degrees the carb needs to be rich or it won't run. If you were fouling plugs before the mods, your idle mixture screw is too far out. And yes, it could, and probably was, set incorrectly from the dealer. The screw is located in front of the fuel bowl on the bottom of the carb. Turn clockwise to lean out the idle mixture, counter-clockwise to richen the mixture. Try turning it in very small increments, about an 1/8 turn at a time. When you adjust this screw it will be necessary to adjust the idle speed to compensate for changes in the mixture. When you get this setting right, you should never foul plugs no matter how long it idles. Don't confuse yourself with plug readings, you can't get a plug read from an idling only run.