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View Full Version : Expert Jetter's Needed ;)


Ispep1012
08-08-2007, 03:18 PM
Okay I am going through to many mods to soon to keep up with this jetting so, I am seeking advice from all you jetters out there.

01 400ex - 85mm 11.1 wiseco piston, stage 1 hotcam, K&N w/Outerwears, Modified airbox lid (basically off), WB CDI, WB E2 s/o, FMF Powerbomb Header, removed choke plate. I run 94 octane or higher and live in Michigan. What would be a good starting point. I already have a 42 pilot and moved the needle down 1 notch. If you can help me out I will be much obliged.

Regards, Rick
400exrider707
08-08-2007, 03:40 PM
I had a nearly identical setup. First I would ditch the WB cdi, it is only going to give you problems, if it hasn't yet.

Secondly no need to run anything higher than the 94 you're running now, if its jetted correctly.

I would start with a 160 main, needle in where you have it, the 42 pilot and 2 1/2 turns out on the fuel screw. Then ride it and work from there.
honda300EXtreme
08-08-2007, 06:08 PM
yea as said above

i would throw in a 42 pilot, and start in the 160 range so you can at leat get a baseline and fine tune it from there, then adjust your air/fuel screw
JOEX
08-08-2007, 08:28 PM
Do you have the needle down one notch or the needle clip down one notch? There is a difference.;)

Just to clarify for others who may read this thread:)
Ispep1012
08-09-2007, 07:59 AM
I have a 160 main in it now, I just have not had a chance to do some plug chops. The needle clip is moved down so the clip is on the 4th groove from the top(raised needle). Also what plug would you guys recommend with the 11.1 8Z or 9Z?

Regards, Rick
honda300EXtreme
08-09-2007, 03:18 PM
i would stick with the 8z
Ispep1012
08-09-2007, 08:48 PM
Awesome! Thanks for the reply's guys. I had a chance to run it today for some time trail riding and my header pipes are coloring in nicely. I did realize that I need shocks badly when I bottom out with 30ft out air-time, but that has to wait. As far as the jetting everything seems cool so for but have yet to do the plug chop. I am going to experiment and put the stock CDI in and see what if anything happens. Oh by the way I was running the 9Z plug today. Thought colder the better with the temps. Any more feedback keep it comin guys!

Regards, Rick
Ispep1012
08-11-2007, 02:15 PM
I finally got a chance to do some plug chops today with a new plug. I threw the stock CDI back in and threw my biggest jet 170K in with an new 8Z plug. WOT killed coasted and pulled and I could not see the burn ring at the bottom of the porcelain. Is it possible that I could need a jet higher than a 170 with my mods.
JOEX
08-11-2007, 02:29 PM
Originally posted by Ispep1012
I finally got a chance to do some plug chops today with a new plug. I threw the stock CDI back in and threw my biggest jet 170K in with an new 8Z plug. WOT killed coasted and pulled and I could not see the burn ring at the bottom of the porcelain. Is it possible that I could need a jet higher than a 170 with my mods.
Forget about the color of the plug for a minute....

How does the motor run at the top end?

From what i've read doing 'plug chops' nowadays isn't as accurate as it used to be due to the additives in fuels.
honda300EXtreme
08-11-2007, 02:56 PM
yea JOEX is absolutley correct,, due to additives in the fuel, a plug reading is not always 100% correct..

to me it sounds like your running to rich,, and i couldnt imagine you having to bump up your main any higher since your on a stock carb,,,
Ispep1012
08-11-2007, 03:17 PM
It runs good on the top end. No bog or miss. It doesnt pop when I let off throttle. Even fine when I snap from idle to WOT. If a plug chop is not the best way to read jetting how should I go about doing in then?
JOEX
08-11-2007, 03:21 PM
Originally posted by Ispep1012
It runs good on the top end. No bog or miss. It doesnt pop when I let off throttle. Even fine when I snap from idle to WOT. If a plug chop is not the best way to read jetting how should I go about doing in then?
Dynometer;)

Sound like you're right there though.
honda300EXtreme
08-11-2007, 03:22 PM
if your bike runs strong throughout the powerband,, there no need to keep rejetting...

you could throw in another plug and get some time on it and see how it looks... but it sounds like your jetting is already spot on
JOEX
08-11-2007, 03:24 PM
Another way is to continue raising the main jet until it starts to faulter then go back down.
Ispep1012
08-11-2007, 04:00 PM
Originally posted by JOEX
Another way is to continue raising the main jet until it starts to faulter then go back down.

I might just pick up a few bigger jets for safety sake and try that. Also I did not mention that I removed my choke plate as well.