Was working on a friends YFZ450 this weekend. It wasn't jetted right and she asked me to change her jetting for her. She has a Yoshi Titanium Full Exhaust and a Dyno-Jet kit (I think the jet sizes are different) The largest jet she had was a 150 (the DynoJet needle was in there - not sure what clip.) The air box was on and the spark arrestor screen was in the pipe (seemed lean and didn't want to lean it out any further!)
The riding area is at about 4000' Elevation and the weather was mild (70's). Oh, also. . . she has a K&N air filter.

We will probably pull the air box lid off and the spark arrestor screen off so, air flow should be improved.

What jetting is everyone else running? What elevation do you ride at? What does your air-box look like? What air filter? Spark arrestor screen in?

One more thing. . . oil was leaking from this thing like crazy. Looked like it may have been coming out of the starter (maybe leaking past the starter O-Ring??? Any thoughts? Not too worried. . . she has an extended warranty so the dealer can take care of that issue.

 

I believe the stock jet is a 155 so you definitely don't want the 150... The general consensus I've gathered from others has been almost always for less than 3000 feet but here is what I believe to be accurate 165 main jet, 45 pilot jet, 3 position down from the top on the needle and various turns on the mixture screw but usually see around 2 to 2.5 out on the screw.

 

Again, Dynojet jet sizes are different than stock jet sizes. . . meaning a 150 Dynojet isn't the same as a 150 stock jet. I am guessing from the kit that the Dynojet 140 is probably equal to the stock 150 jet. (This is just a rough guess though.)

The 150 was the largest jet Dynojet had in their kit.

I will probably tell her to ditch the Dynojet kit and go back to the stock needle and use stock jets. I feel bad. . . she spent money on the Dynojet kit and now it isn't worth anything.

 

id toss that dynojet kit in the trash!! i cant stand they dont use keihin jets.

the gyt-r is better and the JD jet kit is even better.

 

You mean This one?

Poor Girl. . . she just bought a jet kit and now needs to buy another one?

I'll probably just tell her to get the jets for now.

What color is your header pipe? How far back does it stay that color? Thanks

 

Do you think that special taper design the James Dean kit brags about is good enough for $65... after all you are only getting 4 jets and 2 needles for such a big price. I didn't happen to notice what size jets it has either... you would think they would say considering they only give you 4.

 

Did you try contacting them?

"Have a technical question about the Jetting Kits or Guide? Contact James Dean directly at JDJetting@comcast.net"

I would atleast try that before you have to get another jet kit. Just a thought.

 

i have my 450 jetted just like dietcoke said 2 and it runs great...CT pipe no lid and a K&N........

 

The question is are you using the Dyno Jet kit?

 

i wouldnt rush out buy another jet kit. I have the JD kit, it was spendy but they dont sell just the needles, thats what I was after.

use the dynojet needle and pick up some keihin jets. a 45 pilot and around a 170 main will put you close.