stock exhaust

[waldo]

I am new to atv's so????????
But I have raced snowmobiles and there in the stock classes there were tricks like in the exhaust a well placed hole(either in the stock pipe or it's muffler) made it run like it had a pipe any thing like that over here????????

[DISHO1]

what kind of atv do you have?

[waldo]

400 EX

[waldo]

BY your BIO looks like your the man to talk to!!!!!!!
stock appearing performance

[DISHO1]

here is a link about modifing the stock exhaust on a 400ex http://home.earthlink.net/~gellett/exhaust/index.htm you can also grind the weld that are in the stock head pipe. if you take the head pipe off and look in the end that connects to the cylinder head you will see the welds. be sure not to remove too much of the welds or it will be weak and break. also, you can remove the choke and shaft from the carb. if you are not using a aftermarket air filter you can remove the screen from the stock air filter support.

[RideRed400EX]

There is a noticable power increase when modifying the stocker, not like aftermarket but it's worth the work. I had trouble finding a big enough bit so I used a step drill. Pull the screen off the spark arrestor then put some hole in the airbox (rejet!) The sound is pretty cool at idle, almost like a helicopter

[waldo]

Now I will look for some one with a stock one for sale and start cuting (is it better to cut pipes flush in first chamber or leave out a little????) any thoughts? end cap flow???

[waldo]

OK I did this pipe mod cut the pipe open cut the inside pipes drilled 1" hole in back plate and reworked end cap DO I NEED to REJET ?????????????

[4punksdad]

I rejetted when I did mine. I went from a 148 to a 165 MJ..........i think I went too far. I backed it down to a 155 MJ and I am trying that for awhile. i also went back to the stock exhaust with no mods.......too much noise for too little gains. anyone who wants a modified stock exhaust, let me know.