Jetting FAQ's

[yfzkalvin]

I have an 06 yfz450, stock pipe, airbox etc. I did a complete rebuild of carb with carb kit, changed the jets to 168m 45p, adjustable A/F mixture screw at about 2 turns out and zip-tie mod. The needle has only 1 groove.

Runs great, no lag, quick response. Problem I am having is that the yfz ran outta gas and had to be switched to reserve long before anyone else did and when it gets turned off it lets out a little puff of a backfire. It's not loud but a little annoying to me.

Normal to run outta gas fast?

What is making it do the little backfire when shutdown?

[RNL]

Anyone done anymore jetting with the new 42mm BSR carbed 450?

[ridingred]

What's up guys, i'm wondering if the 07 carbs jet differently than the gen 1 yfz's?

i've got a 2007 all stock except it's running a uni air filter with outerwears lid, the baffle is out also.

would a 165 or a 168 main jet be ok? i plan to bring the a/f screw out a bit too. It's just a little lean right now with the outerwears lid and the stock jetting still in the carb.

[flavtfan]

I have a question about my jetting(las vegas) I'm going with some suggestions for my 07 yfz and running a 168mj, 45p, 40 leak, stock needle, 2.25 turns out. right now i have an fmf titanium 4.1 slipon, airbox off and it seems like when i stab the trottle i get some popping and it boggs and nearly shuts down. if i give it throttle a little then stab it it sounds and revs up great other than a pop here and there. i get a high idle sometimes too then it comes down a little...still seems a tick high for idle. i also have started getting a light backfire puff when it shuts down. any suggestions on my jetting for Vegas and Dumont. the only thing i know i want to do is go to a 35 leak and get a ncvq needle and put it on the 3rd clip with a uni filter. does the screw have anything to do with the high idle issue i seem to have now? didn't idle like that with the previous jetting 162mj, 42 pilot, 40 leak, stock needle. UPDTATE...went with ndsr needle 3rd clip 1.75 turns fuel screw and all seems good so far. Gonna get the 35 leak on order...NEW UPDATE, added a velocity air filter and went to dumont this weekend. it's running just a little lean. I'm going to either bump to a 170mj or stay with 168 and drop to the 4th clip on the needle.

[team450]

Ok i have looked up and down and can't fine much on the adjustment of the air to fuel screw if you have and aftermarket one. i have one and i would like to know what it dose exactly if its screwed all the way down that is what ? completely off on ? and out like 4 turns or so where it is almost all the way out and what dose it effect the whole range- idle - wot - mid ?

[np342403]

2007 YFZ450
-Lexx MXE slip on
-K&N filter with Outerwear prefilter
-Airbox lid removed

Any recomendations for a jetting setup? Help would be much appreciated!

[redneck-yfz450]

I have a 2005 yfz and was stock, I have recently taken the baffle out off the stock exhaust and modified the air box lid, have a k and n style filter, and took out the cone shaped screen. I just baught the dynojet kit stage 1 and 2. Idk what main jet, e clip setting and mizture setting to use for 3000 ft. Please help?

[Bowtie]

Take the dyno jet kit back, and buy keihin jets. Start with a 42 pilot, 160 main, clip on 3, 1 1/2 turns out.

[redneck-yfz450]

i ordered it from partsforatvs.com and dont feel like sending it back

[redneck-yfz450]

can i get away with using the 45p 160m and on 3 with 1.5 turns?

[Thatoneguy]

Another jetting question, 05 450 bill balance exhaust, air box eliminator, Athena big bore, aftermarket fuel mixture screw.
Sea level about 1600