Pilot Screw Question.....

Just picked up my 426 a few days back and getting aquainted with the bike..I read somewhere on TT that some guys were losing their Pilot Screws and every so often they would seat the screw and turn it out 1 1/4 to 1 1/2 turns to keep from losing them. What size screwdriver do you use to get in there?? Pretty tight! Second question...Is Gas Tank Removal nessessary for Spark Plug Removal or is a special tool available?? Thanks

Steve 01 YZ426F Bone Stock...for the moment

[ April 04, 2002: Message edited by: Steve R. Jacovino ]

Hey Shawn Can I respond to this or will that upset you too!!

Some have reported the screws backing out, i have not had the issue, but go buy yourself some jeweler screw drivers, the come in a variaty pack and can easliy fit under the Carb

Plus a member here (Motoman has a good snap shot of a quick fix screw driver with detailed instruction on building it...

here is the link


Was That OK Shawn

[ April 04, 2002: Message edited by: EgoAhole ]

[ April 04, 2002: Message edited by: EgoAhole ]

I don't think that the screw falling out is a common problem, at least it doens't seem to be to me. I'm going to stretch to guess that most of the people having this problem probably had it set pretty far out to begin with. Someone correct me if I'm wrong on this. You should be able to get to the screw with a small stubby flat blade screw driver.


I have seen acoupl eof posts regarding back outs like that (What you said) setting the screw to far out. Steve stated he has his out about 1.25 to 1.5 turns, Maybe I misunderstood

But thanks for catching that one. I stand corrected

[ April 04, 2002: Message edited by: EgoAhole ]

If you get beyond 3.0 turns out, the spring does not put enough tension on the jet and it may come out. Also, if your that far out, you need a larger pilot jet. I hope you really mean the fuel screw?

You can also buy a Kouba T-handle. It presses onto the fuel screw and allows you to adjust the fuel screw by hand.

For the plug, I've heard you can get the plug out, without removing the tank by using the wrench that came with the bike.

Just pull the fuel line, remove the seat, the 2 bolts in the shroud to radiator, the 2 tank bolts and it's off.


I've had to replace a plug or two at the track (cursing in foreign languages the whole time I might add).

Just pull the seat, the two shroud bolts, the two tank bolts, leave the gas line on and prop the tank up. You can get to it with a "wobbler," extension, and spark plug socket. My spark plug socket has a rubber insert that fits snug around the spark plug so you can pull it out no problem. You can do the same thing with fuel line or similar.

I had to pull the plug at the track about every 1-3 rides and it was a PITA!! After I disconnected the light blue wire my problem has gone away and it starts within 3 kicks hot or cold! Im sold on this mod, it was the best $ I spent on the bike (oh wait, it was free LOL) Later,



Also, if your that far out, you need a larger pilot jet. Don't you mean a smaller pilot?

Out lets more air in?

No, Bill is right in what he said. If the pilot screw is behind the carb (closer to the airbox)it is a pilot air screw...if the pilot screw is in front of the carb (closer to intake port) it is a fuel screw. So since the YZF has a fuel screw, then the more you turn it out, the more fuel your bike gets. So if your over 3 turns on a 42 pilot, then a 45 or 48 jet would work better and the screw wouldnt be screwed in as much! Make sense? Your XR600 is the opposite it has an air screw and in that case you would be right! Later,


Even when properly adjusted, the pilot screw may fall out, mine did. If you ride hard like I do, the vibration and constant jarring will overcome the locking force the spring provides, or the spring may be a little weak(defective)and not hold tight enough. I would recommend putting a small piece of tape over the hole, just in case, why wouldn't you?? It may save you tons of aggravation and $32.45(cost of new screw), just in case you pilot works it's way loose. I don't see how anybody gets the plug out without taking the tank off, how would you pull the large plug wire off?? I had to change my plug about 5 times before I rejetted the carb, and it is a huge pain, but I can now do it in about 5 min 32 sec. You will need a wobble, and a rubber "plug grabber" insert in the socket. One came with my bike, you can use a 14mm box wrench with it, and it works great.

Originally posted by 4:20six:

I don't see how anybody gets the plug out without taking the tank off,

The secret is to yell a lot of curse words.

Works everytime! :)

My pilot fell out and I'm 99% sure it was between 2 and 2.5 out when it ended up on the ground at my track. I haven't had a problem with the new one though.

Garret and Bill are correct. The pilot screw on the FCR carb is simply a fine tuning needle screw that fine tunes the amount of fuel that is allowed to flow through the pilot circuit. Hence, the "fuel screw".

As an aside about changing the plug. I would be very concerned if I had to change my plug at the track without the benefit of compressed air or another inert gas. It's worth considering how much debris collects around the plug that could easily fall inside the head if the the plug is simply yanked out without blowing this area clean first. Plus, shoot a little air inside the weep hole first and the plug cap pops up for easy removal.

[ April 07, 2002: Message edited by: Boit ]

I made a fuel screw aduster with a piece of 3/16 steel brake line and a flat washer. I soldiered the flat washer to then end of the extention that I flared, then I drilled the end of the brakeline to the same diam. of the fuel screw and soldiered to the fuel screw in place. the washer works as a handle. It cost me nothing to make, and I can dial the fuel screw in with the bike running.

You are absolutly right Boit about debris falling into the head..The area should be cleaned and then blown off with compressed air..The track I go to here in NJ is "extremely" dusty when it is crowded and I get nervous when (if) pulling out my oil dipstick..never mind pulling the plug!

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