Guys I searched around and couldn't find much relevant to my particular situation...

Here is some backgroud - I have an 04 STP 700 with about 1300 km on it and decided to try the exhaust mod and use the napa hose on the intake side. Assuming that this was going to lean the machine out I installed a 142 main in the front and a 145 in the rear (stock was 138 front and 142 rear)

The install went well but after taking it out for a ride the thing ran horrible at everything from mid to top end. Low end seemed all right. Tried a low end plug check and tuned my air screws and they seemed all right. But after doing a full throttle run and then a plug check it was horribly rich (I think - the plugs were black!) My buddy on his vforce was there so to try and lean it out i threw in his K&N and even tried removing the plastic cover in front of the intake - which should have leaned it out even more. Seemed to help but still stuttered and sounder like it was popping in the airbox at mid range and full throttle.

After being really disappointed I took everything apart and put the stock jets back in and then did a plug check and found that it was still running rich! Now the thing ran strong before I touched it and is there anyway that I would have to put smalled mains in after all the mods I've done to increase flow? Keep in mind that I haven't touched the needles.

Any ideas or opinions would be appreciated!

I have pics of my plugs after the last run but haven't found out how to upload yet...

 

With those mods you will need to go way bigger. Air box can give you 3 sizes alone, the pipe another 2 sizes. I think you are reading your plug wrong. It is hard to do that. Poping in the carb is usually lean. Just go up 148 F and 152 R and see. There is a better way to read plugs than the color of the center insulator. You can read the outside electrode color. There will be a line on it after a minute or two of hard pulling. The line should not be any further away frpm the center than the 90 degree bend in the electrode. If you look close you will see the line, black on the outside and silver on the inside.

Hope that helps.

ckedd

 

Here is a site showing pics of what ckedd was describing about the line on the plugs electrode. I am still learning how to correctly read the plugs. Every little bit of knowledge helps.

Site on reading spark plugs

 

This is my real login - I was at my dad's farm and couldn't remember my PW so I created a new account...

Point being I am the originator of the post and just wanted to say THANKS!

That is news to me on the subject of plug reading and am I to understand that a light coat of balck suit on the outside ring is about right if not a tad rich and that if that ring doesn't extend all the way around to the electrode (in factg has some tan next to the electrode) it is on the verge of being too lean?

I always read the center of the plug this is great advice - I going to try and pick up some larger mains and see what the result is!

Thanks again guys - the help is much appreciated!