Anyone willing to help? Jetting-WR/YZ timing

[MOmilkman]

Got it YZ timed last night and now my bike runs like a total piece of crap.

It ran great the first half lap around the block, but then all hell broke loose.

Theres was hesitation and backfiring all the way up and down the powerband.

Never ever had a issue when it was WR timed so I know its the YZ timing/jetting thing thats giving me the problem.

Anyone mind telling me where to start? ?

p.s. Im 99.9% sure I did everything right when changing the cam timing.

[Hick]

Wow. I hate to say this Moo but you must have done something wrong. In my experience changing the cam timing has no real affect on the jetting. At the most it changes the idle characteristics a bit, I may have tweaked a fuel screw slightly...

Keep in mind both the WRs I've done this too were 426 that already had the same jetting as my YZ.

Anyway, you stated it ran great, then started running like crap. Hmm. Don't ride it anymore, check your cam chain tensioner, then recheck the timing.

I'm guessing you did not touch the carb while doing this since it isn't necessary, the only thing I can think is you jumped a tooth or two (or more) after the first half-lap around the block.

[MOmilkman]

Hick,

Ive been going back through the archives looking for info on this and I noticed you mentioned that jetting has nothing to do with timing in several other posts. I do believe you.

However, how could my tensioner not be working properly? After intalling (the tensioner) it, I released it with the screwdriver. So what could I have done wrong there?

Im starting to wonder why I messed with something that was running good to begin with. ?

Im going to St Louis SX tomorrow so I wont have time to mess with it again until monday night.

I may just change it back and be done with it... hopefully

[Bill]

Darrin,

I used the EKP set up after lot's of developement and now the EMM. Taffy helped me get mine, spot on and your bike is much like mine. Try what's in my signature and you should be dang close.

Bill

[MOmilkman]

Try what's in my signature and you should be dang close.

Bill, Im gonna do exactly that. I'll order what I need to Tues and then try it out next weekend. (hopefully) If this dosent works I'll probably just change it back. Mabye this will do the trick.

Also Bill, I'm not much of a carb guru at all so could you explain what some of this jetting stuff in your sig means:

EMM #2, (needle)

38PJ, (pilot jet)

55PAJ, (???)

158MJ, (main jet)

160MAJ, (???)

60SJ (???)

and 1.5 FS (fuel screw)

[MN_Kevin]

Darin,

Going w/ Hicks initial feeling I too immediately thought something went wrong w/ the YZ timing thang UNLESS it has something to do w/ plug fouling...???

[MOmilkman]

Thats what Im hoping for too Kevin. I should have pulled the tank off and checked that already but I got back from the St Louis SX late tonight so I havent had a chance yet. But I will first thing tomorrow.

Im hoping the plug is coated black. If so, then I just have to learn a few new things about carbs. ?

We will see tomorrow, and I'll let you know.

[MOmilkman]

After making that last post I couldnt stand thinking about it anymore so I went out and checked it.

And its black.

It was definatly running way too rich.

Im going to get Bills jetting settings and give it a try.

Cant hurt.

[cowboyona426]

EMM #2, (needle)

38PJ, (pilot jet)

55PAJ, (???)

158MJ, (main jet)

160MAJ, (???)

60SJ (???)

and 1.5 FS (fuel screw)

PAJ= pilot air jet; MAJ= main air jet; SJ= starter jet

[Bill]

I'm no guru. I asked taffy and he helped me out completely.

Well if I'm wrong, taffy will correct me. The reason we can go so much leaner on the pilot and main jet is because of some ratio corilation between the pilot and pilot air jet also the main jet and main air jet. This ratio is what makes the leaner jetting work. The start jet is what controls the fuel wihen the choke is on. Think of it as the choke jet. The location for the jets is indicated in the manual.

Please bear in mind, I also did the KL/taffy mod to my accelerator pump also. The only changes I had to make, was in needle position.

Bill

[MOmilkman]

Thanks cowboy for clarifying those.

Bill,

I guess Im gonna have to familiarize myself with where some of these other jets are before I start. (PAJ, MAJ)

All my jetting is still bone stock except for the MJ. Do you know what the stock jetting is on a 99WR for all these jets? That way I know what I need to order and what I dont before I even start.

[cowboyona426]

Milkman- the PAJ and MAJ are behind the intake bell- you have to remove it to get at the jets. You can see them with the intake bell installed, but you can't get them out.

[MOmilkman]

Ok, I seen those when I was checking my squirt duration, so no problem there.

What about the starter jet? Where might that bugger be?

Never fiddled with that or the air screw.

BTW: Hick, I checked the timing just now and its still right where I left it at YZ timing, it didnt jump. So I'd think it has to be jetting.

[Hick]

Well, you've tried YZ timing, maybe you should try YZ jetting. I don't have any experience with the 400s so I can't really help you there...

The starter jet is right next to the pilot jet, in fact it is possible to mistake one for the other, until you pull it out that is. Don't worry about the starter jet, or choke jet as I like to call it. If your choke does what you want it to (read: you can start your bike w/ the choke on) then just leave it alone.

If it were me I'd make a note of the current jetting, then change everything to stock YZ 400 jetting and go from there. You will probably need a needle, main and maybe a pilot air jet.

[cowboyona426]

Oops, sorry Milkman. I forgot one. Doh! ?

[edareus]

Darin, if you go to the full YZ Jetting I think you have to deoctopus at the same time. Chris checked into this so he would know better than I but I know there is another jet that is way different on the YZ.

Ps. We will be down to Chadwick next weekend and the race was great!

[MOmilkman]

Ok, thanks Hick, Im getting it narrowed down now.

Does 1.5 FS mean 1.5 turns out from full in (clockwise)?

, if you go to the full YZ timing I think you have to deoctopus at the same time.

Oh man! Is this true!?

I need to get this figured out so I CAN go riding this next weekend.

If it is true, I think Im just gonna change it back to WR. I think Im getting in way too deep if I have to do this too. (de-octupus)

Anyone know for sure? ?

[edareus]

Darin, I am trying to find out for you. I emailed Chris(Hurricane) and either he will post or email me back. Soon as I find out I will let you know.

Do you still need that plate for the James now mod??

Eric

[edareus]

Man, I edited my earlier post but you quoted me so I'm burnt. I meant to say YZ Jetting not YZ timing. Ok, here is what Chris said.

"I really don't know for sure. I think you might have to change all of the

jets except the ones that have to do with the deoctopus mod. There are two

jets that I know are still stock on my bike and those are the ones I would

have had to buy to deocto(one is the apj and I forgot what the other is). I

had to put 175 main in my bike when I switched to a yz exhaust but that is

all I've done."

I think the starter jet was the other one. He was already YZ timed when he bought the bike. We started to deoct his bike one week but no one had the jets so we bailed on it.

Sorry we can't be more of a help.

[MN_Kevin]

Darin,

De-octopusing is wicked easy.

You must remove the ENTIRE octopus. You will have to cap two of the nipples on the carb body itself.

Re-connect your hot start bypass.

You have EVERYTHING you'll need right on the carb EXCEPT FOR the two rubber caps. Find those at an automotive store.

After fiddling w/ the caps, I used some silver soldier, torch and flux to fill the nipples permanently. My rubber caps were suffering from dry rot.

Missle (Simon) may be able to help you out w/ pictures(?). It is also in the archives somewhere written by Clark Mason from 1999.