Pipes, filters, lids on/off, cams, sound familiar? Well, we are all at it, modifying our Z400s. The one thing in common with all these mods. is the dreaded carb rejetting. To help those thinking of upgrading their machines or those who have done so and may be having problems, it would be good to hear from those of us that have installed various combinations of pipe, filter, cam etc. and had them sucessfully dyno tuned to see what the jetting ended up as being. That way a lot of the time consuming trial and error for the new installer could be eliminated if they had the same combination and operating conditions. Any offers?

Secondly, I don't know if such a thing exists but a stock jet versus Dyno Jet / Alba jet chart would come in handy if anyone has this information. I understand they do not equate and Dyno Jet for one are not very forthcoming with this infromation.

Great forum guys, keep it coming!

Happy trails,

Djmz400 [img]i/expressions/face-icon-small-frown.gif[/img]

 

With a Yoshi Comp full, ProDesign filter with adapter, and Hotcam Intake cam at 2000 feet I was running a Dynojet 155 main with the needle on the 3rd groove and 3 1/4 turns out on the air/fuel mixture.

 

KFX 400 = CT full exhaust with 7 disc tip , K&N filter and adaptor with no lid or snorkle

Jetting = 160 Mikuni (same as 167.5 Dyno jet) Stock jet was 132 Mikuni
Pilot jet = 35 Stock was 28
Air screw = 3 turns out Stock was 2 1/2
Needle = lean position

Tuned and Dynoed by Sandtech Racing (same guys that did the pipe shoot out for Dirtwheels)
Dyno 1 = 29.9 on Maxxis 20in Razr 2's
Dyno 2 = 38.4 on 8in Hoosers

The setup CT told me was a 155 Dyno jet and a 33.5 Pilot and take the lid off . I did that and my KFX ran like BIG STINKY SHIAT

 

Oh yes forgot to say lid off and snorkle off!

 

Lid on, snorkle baffle removed, peashooter and wall behind drilled out, 145 main, alba needle #4 from the top and 25 pilot, 3 turns out.

Perfecto.

 

Stock mods.

Lid full of holes and filtered with polly media.
Stock muffler with spark arrestor removed.
25 pilot, 1 washer under stock needle, 145 mikuni main, 3 turnes out on mixture screw.
Near sea level,

Gave me a big boost in mid range power.

 

HMF recomends taking off the Snorkel, and going to a 170 main jet for their Slip-On Exhaust. Does this seem like a BIG jump in the Main Jet for just a Slip-ON.

If you go to their Website HMF Slip-On for KFX400 that is what it says.

 

RPM- Go with what they recommend and if it works out then great...but if it doesn't, hopefully that will put you in the general area and you will have something to work with. Dirt Wheels graph showed a nice smooth curve on HMF with the 170 main. Remember that everyone's jetting will not be the same so expect some fine tuning that will need to be done, but you will become a pro after a while and changing the jets will become a simple task. Good luck!

 

Here is a site that will show you what the dynojets are to mikuni http://home.swbell.net/tharthun/home/mainjets.htm

 

Dynojet and the Mikuni jets for the Z are the same. I'm guessing you're showing the chart that compares the hex Mikuni main jets to the dynojets. But in this case, they are the same. Mikuni makes 3 types, small round (z type), big round, and hex.

As for HMF, I've heard more people say it ran like crap with a 170 than not. That's way too fat and is partially making up for no needle adjustment (I wouldn't want to tell everyone to adjust their needle either, especially when it requires purchase of an aftermarket needle). They got cool pipes, but the 170 even with the lid off is still a little fat in any case. I also think it's so people will say "Wow a 170, that pipe must really rock!"

Well, these things ain't lawnmowers, they have 3 or more fuel circuits.