yz timed, won't start

I changed my WR to YZ timing today, followed all directions to the T, and it won't start. Could my jetting be that far off? I bought this bike used so as far as I know the jetting is stock. While kicking it over, the bike will fire a couple of times but then die again. What do you think? What kind of jetting should I be running in 30-60 degree weather at about 800ft above sea level?

If your bike was running prior to doing the new timing, and you did it correctly, it should start now too.

I'd replace the plug and try starting it again.

See Ya,


I have seen this before. Try to bump start and ride the bike before you go and rework the cam timing. If it runs well and rips harder in the mid range and top end you then need to work on your jetting for the YZ timing. :cry:


I just did the same thing (see my post below) and experienced very similar behavior. The bike started on the 2nd kick. Ran for about 5 seconds. Died and would not for the life of me start again (my worn out knee can attest to that). My jetting was a bit rich but still good for the bike at WR timing but when I finally did get it to run on YZ timing ( I live on a big hill) it seemed really rich and would smoke (black smoke) when revved.

I took the time to put it back to WR specs and it ran fine. I would check your jetting since I bet that is the problem.

To get it to start after I bumped it down the hill I pulled the plug and cleaned it (very wet!) and then started it without the choke. From my post below the person who responded said that stock jetting worked best. Again, I would bet that the previous owner modified the jetting or at a minimum needle height!

Best of luck and Merry Christmas!


Sorry one more thing!

What year is your WR? I have a 99 and have the factory manual (came with the bike). If you don't have or need the stock jetting info for that year just let me know, I would be glad to provide it!

Thats what i was thinking was a jetting issue. I am just not a wiz with jetting so i guess i will just have to learn now. I am going to start by cleaning and maybe replacing the plug. If that doesn't work, off the carb comes i guess to check that out. Darndest thing i have ever seen.

thanks TTers and Merry Christmas.

When I retimed my sons and my WR426's I did the YZ jetting at the same time. It made the bikes a lot easier to start than they were before. I only use the hot start after crashes now. Before the mods I had to use it everytime I started the bike after it was warmed up.

I'm an average mechanic, at best, but IMO if the bike ran before it should run now. With my WR timing/jetting I got a few fouled plugs, since changing I haven't had this problem.

Good luck.

See Ya,


That is my problem I am thinking, I still have the wr jetting in the carb. What are the YZ specs as far as jetting?

Its been years since I did the mods but if I remember correctly it was

EJQ needle and 168 main.

I left the PJ and MAJ stock.

There were some really good jetting threads here a few years ago.

you might try searching for them.

It seems like EMM with a small main (160 to 162) and ELN or EKN with a 165 to 168 were also very popular.

If your looking for the threads they'll be late 01 and early 02 dates.

See Ya,


I have a 99, stock jetting, already did 2 YZ timing mods and reversed to WR, currently I use YZ

last plug in the bike lived up to 1.800 miles, electrode colour was always light brown

for the last 300 miles, cold bike died often when idling or gradually adding throttle to warm it up and also sometimes it cut off when hot

didnt really know what the problem was (I presumed weather changes and pilot screw)

now I changed for the new plug, and cold idling and throttle response is OK

installed the iridium plug CR8EIX, to test it for endurance, since it is twice the price of regular CR8E

Ok, so after a long search last night I have found Bill's settings to be the most talked about three years ago for a baseline on yz timed wrs. EKP #4, 170 Main, 50 Pilot and #100 main air jet. Does this sound right?

Yes it sounds right but I would go with an EMM needle for winter and EMP needle for summer. Or just buy the JD jetting kit and go with his needles. JD needles are close to the EMM ( blue) and EMP ( red) but JD has a leaner 3/4 throttle range on both). Getting the right needle set up for your mods is the hardest part. I got 13 needles to prove it! :cry:

Go with the 50PJ , 100 PAJ and 170 main. those are good starting points. :cry:

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