Jetting

[zrpilot]

I replied to a previous post abut jetting changes. I think it important to understand that a 5 point main jet change makes very little difference in power (assuming the jetting is close to begin with, rather a more significant change in the AF ratio.

Here are some dyno runs that I did on my 400EX. I hope you enjoy.

This first one is the 6 point main change. I went from a 152 to a 158 main. No a big power difference, but look at the AF. The 152, for me, was a little lean.

But I would venture a guess as to say the 400EX would be JUST fine running this lean (as long as it did NOT detonate!!!!)

[zrpilot]

When I started the dyno run, I was jetted a follows:

Main 175
Needle: #3
Pilot #52

Ended up at:

Main 158
Needle: #4
Pilot #52

Interestingly, I thought my 400 ran pretty good before on the larger jets. Of course it ran much better after!!!!

Notice the power and AF changes. This is why a dyno can be an invaluable tool for tunning!!!

Below is the begining run and final run.

[zrpilot]

Now here is a graph showing what the needle change can do... notice how the whole a/f curve changes across the entire middle RPM range...also notice how I gained nice power in the mid-range yet lost it on the top. A main jet change would take care of this.

Note there was not enough warm up run once the needle was changed, so the picture maybe a little different after some warmup.

[zrpilot]

What does warming up have to? Here are a few runs with NO jetting changes, just successive pulls, notice the change. Is it warm-up? I think so...

Note all these runs were done in a 2 minute time span... no changes....

[zrpilot]

I hope that helps everyone understand jetting a little better. I am CERTAINLY NO expert, but I did learn alot during my time spent on the dyno.

It cost me just over $100 and for me, it was money well spent.

Unfortunately my 400EX has changed dramatically from when the dyno was done. I now am running a 450R carb and a Sparks X6 exhaust.

When I did this dyno session my 400 had the following mods:

87MM Wiseco 11:1 piston
HRC cam
Port cleanup by GT Thunder
39MM FCR carb
HMF full exhaust system
EHS Racing air box lid
Foam style air filter.

[vAnS_77]

I need to run my quad on the dyno after I get it together. CRF450R 400ex LSR FRAME. Not gusset stock...Racing frame :d. I'm looking for it to produce around 50+. It's going to be a beast but the quad was used. By the way does anyone know of a dyno in northwest indiana?

[zrpilot]

Bump for everyone to read

[buster024]

Well done dude.......as usual. :D