Jetting the 07......WTF

I am sure the 07 WR450 is a great bike but posts about jetting has me wondering. My belief is a lot of folks are jetting way to rich. It can't be drastically different than my 06. I feel sorry for newbie jetting mechanics so I'll give my scoop until someone like Indy comes up with perhaps a new jetting chart for newer WRs, that is if the 07 jetting is actually different. Caution, I don't have an 07 so I don't really know.

AIS removal does not require re-jetting. Not even doing the free mods does necessarily. Maybe a pipe would. New bikes run a little hotter at first because they're tight so don't idle them around.

I'm running a 40 pilot jet (because I have ACV deactivated) - 2 turns, JD red #5, 168 main, 70 starter jet, 100 MAJ and 0 leak jet (BK mod: .2-.3 second squirt). Temperature is 45 deg F and altitude is 3500 ft.

My mods: All free mods, FMF titanium powercore (very free flowing muffler), FMF powerbomb header, YZ exhaust cam and 13/50 sprockets.

My 18 year old son says it has never run better. It is a wee bit lean (pops 2 or 3 times on decel but this doesn't necessarily mean its lean with ACV deactivated) but will do better in warmer weather. It has instantaneous, scary throttle response and continues to jerk your arms out of socket as the engine revs......I can't keep the front wheel down 1st through 4th even with a bald rear tire.

I'm not saying my bike is inevitably faster than Joe Blow's but I know its jetted right. So good luck to 07 owners in jetting your bike.

I am sure the 07 WR450 is a great bike but posts about jetting has me wondering. My belief is a lot of folks are jetting way to rich. It can't be drastically different than my 06. I feel sorry for newbie jetting mechanics so I'll give my scoop until someone like Indy comes up with perhaps a new jetting chart for newer WRs, that is if the 07 jetting is actually different. Caution, I don't have an 07 so I don't really know.

AIS removal does not require re-jetting. Not even doing the free mods does necessarily. Maybe a pipe would. New bikes run a little hotter at first because they're tight so don't idle them around.

I'm running a 40 pilot jet (because I have ACV deactivated) - 2 turns, JD red #5, 168 main, 70 starter jet, 100 MAJ and 0 leak jet (BK mod: .2-.3 second squirt). Temperature is 45 deg F and altitude is 3500 ft.

My mods: All free mods, FMF titanium powercore (very free flowing muffler), FMF powerbomb header, YZ exhaust cam and 13/50 sprockets.

My 18 year old son says it has never run better. It is a wee bit lean (pops 2 or 3 times on decel but this doesn't necessarily mean its lean with ACV deactivated) but will do better in warmer weather. It has instantaneous, scary throttle response and continues to jerk your arms out of socket as the engine revs......I can't keep the front wheel down 1st through 4th even with a bald rear tire.

I'm not saying my bike is inevitably faster than Joe Blow's but I know its jetted right. So good luck to 07 owners in jetting your bike.

ACV?

Your jetting is way different than mine, but it sounds like the results are the same.

ACV?

Your jetting is way different than mine, but it sounds like the results are the same.

California and Montana can have way different altitudes. No comparison.

California and Montana can have way different altitudes. No comparison.

Thats why I stated that my altitude is 3500 ft!

I also wonder about the jetting, because an 07 wz 450 has a 160 mainjet. I think these new o7 wr are cammed for alittle more bottom and midrange. I rode my 07 yesterday at sea level and it ran good with 170 main and 48 pilot but sounded rich. Im riding tomorrow at about 4000 foot and I will put a 165 main back in and see if I can tell a difference.

Thats why I stated that my altitude is 3500 ft!

I missed the fact that you don't have an '07. So now you have me totaly confused! What are you jetting?

The only difference should be a smaller main jet and a little change in the fuel screw! If you had an '07 WR450F.

In all fairness, I need to clarify......I forgot to mention that I have a Powernow installed on the intake side of my carb and that usually makes a bike run richer and is one reason why I can run with leaner jetting. Sorry I had forgotten about that but I still think folks are jetting their 07's to rich.

Derwud2........what is it about these sentences in my initial post you say you don't understand?

....It can't be drastically different than my 06....

......Caution, I don't have an 07 so I don't really know.....

are you trying to help the newbies or confuse them more with this post? you want to give them the scoop on jetting but you've gone much further than needed to get a 450 to run right. there's no reason to bypass the acv and the bk mod is for 426's. the new guys will be fine with a 48 pilot and a yz needle. a fourty leak jet will help if there is any bog. uncap the pilot fuel screw and learn to adjust it. if the smallest restricter is removed from the exhaust and the snorkle is removed from the airbox, they will need to go up at least one size on the main jet.

you say your bike rips. i bet it does! full fmf exhaust, yz cam, and one tooth smaller countershaft sprocket. it better rip with that set up! heck, you built a yz with lights.

i have no problem with making the bike perfect, but for a guy that just rolled his first wr off the show room floor, the basics might go a bit further.

In all fairness, I need to clarify......I forgot to mention that I have a Powernow installed on the intake side of my carb and that usually makes a bike run richer and is one reason why I can run with leaner jetting. Sorry I had forgotten about that but I still think folks are jetting their 07's to rich.

Derwud2........what is it about these sentences in my initial post you say you don't understand?

Well now, every bit of it! Since you don't say what bike you are working on...

Look at your title (posted in the WR4**) section and you should be able to see my confusion since I thought you were trying to jet a '07 WR450F..

I was going try to help you but.....................

Oh, by the way, the 07's don't use the same jetting as the '06...

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now