Full yoshimura exhaust jetting?

[bigbearkid4x4]

hey guys im trying to decide on a exhaust for my 2002 400ex and its between a full hmf and a full yoshimura rs-3 comp. the hmf comes with the exact jetting you need and its that simple. the yoshimura will i have to get a jet kit or can i buy the certain jet from my dealer? i dont really want to get a jet kit and have to guess on what jet to run. any of you guys running a full yoshimura if so what jetting are you using? thansk guys

[GPracer2500]

Originally posted by bigbearkid4x4
[snip]...the hmf comes with the exact jetting you need and its that simple...[snip]

Unfortunately, it's not that simple. You're going to have to go through the same jetting process no matter what exhaust you choose.

I've heard from others on here that the HMF jetting specs are WAY to rich [shrug]. And regardless, your intake setup, elevation, temperature, etc. will change the jetting requirements for your quad. There is no magic list of jetting specs that will tell you what you need to run in order to have spot-on jetting.

Finding the correct jetting for any individual quad is a process. Outside information can help guide you towards a starting point but it will never be perfect without experimenting. And sometimes "jetting specs" from elsewhere (even pipe manufactures) can be way off.

As far as "jet kits"--I say skip em'. The aftermarket needles that come in kits for various bikes can somtimes be a big improvement (the GYTR needle for the YFZ450 comes to mind) but the stock 400EX needle (99'-04') works well. Find a local dealer that sells individual original Kiehin jets or buy them from an on-line vendor. Get a range of sizes that you think will be close to what you need and start experimenting to find out what YOUR bike in YOUR environment likes/requires.

That's my $0.02

[ride_red666]

i would get the jet kit. i have the full yoshi and a 170 main jet. my lid is off. elevation somewhere between 3000- 4000