What The Heck Could I Have Done Wrong--

I have a 99 WR 400 with approx. 800 miles. Prior to making the changes below the bike always started first kick hot or cold and carbureted perfectly. Last week I checked my valves and 1 intake and 2 exhaust valves were tight. I got the correct shims and while I was there I changed the exhaust cam to ZY timing (followed instructions and it appears to be correct).

The bike has the stock jetting and when I started it everything seemed ok just some blubbering from half to full throttle.

I ordered the Baja designs' WR timing kit (OBDVR needle on 4the clip position, 172 main and 48 pilot, fuel screw at 1 ¾ out). I changed all of that and the bike starts harder and it is running ratty ---- idle is rough, still blubbers from half throttle up. so what the @#$%^ this could be caused by?

I forgot, when i blip the trottle all the way open and let go, the motor dies.


[ November 01, 2001: Message edited by: Rocky ]

Ahhh...I see...you did the ZY timing! You should have done the YZ timing!!

Just jiving you. Actually it sounds rich to me. Start with the pilot screw and start turning it in (leaner) and see if things improve. If so, keep going with it. If you're getting inside one turn on the screw then drop you pilot jet down. Still blubbering, but starting/idling better?? Then drop the needle down leaner(raise to clip up a notch.) One clip position can make a big difference!


When I changed to YZ timing I went to a ELN #3 needle. I'm up in altitude from you, but I would expect you would find the "E" needle leaner and to your liking. Try sudco for needles or search for jetting files with Yamaha part numbers. Everything else sound like your in the right direction.


Just for kicks, and since you're already using it, try clip #3, and #2 on that needle.

Re-read those timing instructions just to be sure you got it right.

Check that your fuel screw hasn't worked it's way out (it's happened to a few before).

Those jets are pretty close to what I'm running right now. I should run fairly well on them with an open exaust and at lower elevations. (I ride < 3000ft)

Also, they suggested that fuel screw setting, but that doesn't make it the best for _your_ bike. Try turning it in too.

If you have had the carb completey apart (cleaning), make sure that when you reinstall(ed) the pilot screw that you dont/didn't forget to reinsert the washer, oring and spring WITH the pilot screw. I spent a while figuring out where the spring lying on my workbench came from.... if it hadnt landed somewhere visible I would have been in trouble as I did not notice it fall out when I removed the pilot screw.

i don't know whether you've an open pipe rocky but i would say that first, you're paying for doing too many changes at once. and secondly you're rich every where!

the burbling at half throttle is a rich condition. your first job should be to go to a 168/165 MJ. this will be the equivelant to knocking your needle down (leaner) by 1/2 clip. that done your needle will probably need another.

what you can do is drop the needle one clip at a time until it pops on decel. NOT at low revs as you turn into the corner but as soon as you closed it!

once it's done that you can go back up 1/2 a clip using a washer under the needle clip.

THEN look at your pilot system which appears to be virtually dripping in fuel!!!

a 75PAJ and a 48PJ are not compatible. some lads will tell you #100PAJ some will say 45/42PJ to balance them out. i like the 4245 route.

it may turn out to be something else but i think it's so rich that you're stalling.


hey rocky

i have a slection of jets and needles if you want to try them out. lets go for a jetting and dial it in ride this weekend

Hey Taffy,

You were right in saying that it maybe something else!!

I think that I screwed the pooch on this one. This morning I tore the top end apart and upon rechecking the exhaust valve clearance I found out that initially when I had checked the clearance – my feeler gage had another blade stuck to it so the clearance seemed too tight. Because of that I had put smaller shims and as the result the clearance was way over the limit. So, I put the old shims back in and with the correct feeler gage the clearance seems OK.

Then I put the clip on the 3rd grove of the Baja design needle from the 4th grove. Changed the pilot back to the original 45 from 48.

Fuel screw set at 1 1/2. Well when I restarted the bike it ran awful at idle so I turned the fuel screw in (I don’t know how far – maybe les than one turn) the bike idles well now. Did not get a chance to take it and see if the main (172) is still too rich

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