I got some questions on My 400EX. The engine is all stock, it has a K&N air filter, a High-Rev box, 18" terf tammers, +2 A-Arms, Elka shocks, Durablue axle, and the End Cap removed off the stock silencer. The question is: If i punch or drill holes in my silencer will I have to up the jetting? Will punching or drilling out the silencer Give me more power, Low end, Mid, or Top end? I'm also thinking about drilling holes in the top of my air box to increase air flow. Will this give me any more power, and will this effect my jetting.
If I were to do both these mods What other things would I have to change, and what jet size would you recommend. Thanks. Is there any other cheep mods I can do to help my engine out?

 

yes you will have to rejet when you drill holes in the lid, i recamend taking the whole thing off, ive never heard of drilling holes in your pipe, but from the sound of it i dont recomend it, if i were you i would get a full pipe(sparks,hetrick) or at least a slip on and grind the inside of the headers, and you could also buy a cam and piston(i dont recomend hotcam's yes they do cost less but everydays they are breaking left and right and as for pistons i would recomend J.E. or ross

 

I dont have the money right now for that stuff, I just stuck $2,000 into it. I do have the lid off my silencer. The question is if I drill holes inside the silencer, With the lid off look inside the silencer and there is a plate welded in there with a one inch or so hole in it for flow. What if I drill more holes in that plate, will this help me out? Also about the header pipe grinding the welds down; I'v heard about this, Is this hard to do and will this give me more power and if I just grind the welds down in the headers will I have to rejet? Thanks.

 

IT all about the flow. On the inside of yor head pipe you may find some weld build up. Take a Dremel or die grinder and smooth them out. This may not change you jetting needs. If you exhaust is stock just wait and get a slip on. If you plan on going big bore at some later date than get the full exhaust.

I have heard of people making thier stock muffler shorter but not drilling holes in the top of it.

Smitty

 

dont drill holes in the air box lid, just take the whole thing off. Takin the snorkel off helps too