can someone explain to me how to take the jets out of a carb and what jet sizes i need to use since i drilled holes in my airbox. i live in south central PA

 

I'm wondering the same thing. I don't know much about 4-stroke motors.So when you put on a pipe you have to change jets and get more air flow?

 

Since I ride a Warrior with a Mikuni carb & don't remember much about Keihins, I't try to give you a few basics. Look at the bottom of the bowl to see if there is a fairly large plug-type nut there. If so you're in luck because that is the main jet access plug. Just remove it to get to the main jet being careful to use exactly the correct size wrench, preferably a box-end as the metal is not very hard. The main jet is right inside & you'll need a jet wrench to remove the main jet.
Now, if you don't have the plug in the bottom of the bowl, forget all of the above because you need to remove the bowl itself to get at the main jet.The Keihin probably has 4 screws holding the bowl onto the carb body. Again, be very careful removing those screws as the heads strip easily & on Yamahas at least, the factory puts them in WAY too tight! The main jet will be right in the center of the carb body..a little brass screw.
If the only thing you've done to the bike is the holes in the lid, I'd pick up two main jets, one & two sizes fatter that your stock. Put the larger one in first to test. Do a test ride at 3/4 to full throttle for at least 1/2 mile for any engine blubbering .Cut you engine right where you are & pull your plug & read it for correct mix. Black electrode means too fat, switch to the lower size jet & test again & pull the plug..tan or brown electrode means proper air fuel mix Replace the plug & go ride! You now have an extra main jet to use when you do further modifications to your air flow.If you still are having problems with all of this, feel free to e mail me & we can go into it further. It's really not brain surgery & takes longer to explain it than to do it.

 

hondatrx300ex,
Yes, you need to Re-jet with the addition of most any pipe, not to get more air flow, that's what the pipe is supposed to do. You rejet to obtain more fuel flow to compensate for the increased air flow. Otherwise you will have a lean condition resulting in excessive heat buildup, and if really lean, piston, ring, & cylinder scoring, and even piston breaking, etc.

 

I was talking about putting on a different air filter to get more air flow.or put holes in my airbox lid.