Full kit v.s Slip on

[400EX_305]

I was wondering if anyone can clarify the biggest difference as far as power goes between a full exhaust kit and a slip on. is there really that much of an advantage to get the header pipe too??

[BossHogg420]

if u plan on doing major engine mods go full system, if u plan to keep the motor relatively stock slip on is all u need

[Wheelie]

Stock to lightly modified engine, go with a slip on.

For a highly modified engine, a slip on or full system would work fine. The stock EX headpipe is actually a good piece and there is little to be gained, if anything, by going with a full system. Even with a highly modded engine.

[bbender85]

some guys port the stock header; the welds just inside the pipes where they bolt to the engine are quite thick... you can really hog them out from pics i've seen on here.

it's on my winter to-do list.

[raw67]

I went from a pro circut t-4 to LRD full system and the difference was really impressive. it all boils down to money. i paid 439.00 for my full system at yamaha of troy. it was worth it to me. my stock 2005 with k&n, rejetted and lrd full system is faster than my 2003 440ex with k7n and t-4 slip on by 2 bike lengths. without the k&n and full system the 440 was 4 bikes faster. this was tested on pavement with same body weight and bla bla bla... just giving you my personal opinion an experience.

full system on stock internals is only about a HP difference from the slip on. However when modded more the full system can make that 1HP or less into more. The stock EX headpipe is actually bigger than it needs to be. They oversized it belive it or not from the factory. I have seen ever 440's with just slipons and they hauled a**. Sometimes you will lose bottom end with a full system

[jeepguy46126]

Raw67 what jets are you running with the full lrd setup ?

[400EX_305]

im probably gonna go with an HMF sport series slip on. i have a k&n and a rev box, what jet size should i start with, i have an fmf jet kit.

[raw67]

To JEEPGUY46126:
Im using a dynojet kit from LRD
pilot = 38
air mixture screw from closed position = 3.5 turns
needle = using LRD needle 4 slot from top
main = 170
my elevation in indiana is 1000ft
however mine seems to be rich