YAMAFREAKINDOG!! Cold blooded beast!


Take a look at this site, www.carbparts.com/keihin/needles_tuning/jetting_your_carb.htm , it may help. I was having problems starting my 02" 520 EXC. It is a California model and the jetting was all screwed up (the dealer didn't have the jets that were supposed to come with it... :) ). I could barely get the bike to idle without having the idle turned WAY up. After finding that the idle jet was a #45 rather than the #48 listed I changed it to a #48. With this change I could get the bike to idle fine. The needle that came with it, I think a DVR, was really lean so I dropped it 2 clip positions. I just recieved my OCEMN needle yesterday so my jetting days should soon be over.... :D thanks James Dean. I had just put my new Kouba fuel screw on before I left to ride at Stonyford, if you don't have one you should. Anyway, to make a long story short the bike was still hard to start. Monty showed me this technique to adjust your fuel screw, hopefully that's what your dad's problem is. Crack the throttle about a 1/16 with the motor running. Adjust the fuel screw accordingly until you get the most snappy response. You'll hear the motor cleanup when you get it right. Look at the chart at the website link (jetting your slide carb,)and see the impact the fuel screw has especially between idle - 1/8 throttle.

Good luck,


It's all about the jetting when the temps change, especially with these 4 strokes.

When are we going to get fuel injection anyways? It is going on 2002! Arctic Cat offers it on some model snowmobiles, and it performs very well. Hopefully in the next few years we'll see at least one competition motorcycle with it.


The stock pilot jet is appropriate for about 70 degrees. You need to go at least 2 richer (if you have a 42 go to a 48) in the pilot.

Very simple to change. Drain the float bowl, remove the bolt at the bottom of the bowl. Use an appropriate screwdriver and remove and replace the pilot. See the microfiche or your manual for an exploded view.

Once you get that changed out and the beast starts you probably also need to richen up the needle one or two positions (raise the clip which lowers the needle). Search this site for instructions. It's way easy and no worse than any other normal maintenance item.

Jet it properly for the temperature and you will be fine.


Steve T

I'm having the same problem that Chris's father is. My 01' runs like crap when it gets cold. Hard to start, fouls plugs, and sometimes just doesn't run right.

I also have stock jetting, but I'm changing that tomorrow.

But I have a question, why does a too lean condition cause the plug to foul ????



John...indeed....too lean should make the plug virtually impossible to foul....I was thinking the same thing...it just makes sense to me.

It wouldn't be so frustrating, if my bike didn't fire on the second or third kick....stone cold...but it is truthfully inexcusable to have a 4 stroke loading plugs in cold weather, I'm sorry.

I know my dad would sell his 426 to someone if they wanted it, he's sick of the starting crap, and at 5'6" it's tough for him to get it going at times when it is stubborn.

Anyone have any thoughts as to the ether I mentioned in my original post??

Buy the electric start kit!! Really - you need to rejet the thing for cold temps. I haven't even tried to start mine ( it's 9 degrees ) I will go up on the main and raise the needle first.

My dad and I went up to ride yesterday with my uncle. We ended up going into a snow storm, and rode nevertheless. We spent the first 45 minutes out in the blizzard trying to get his POS to start!! I kicked my beauty twice, and she fired. FORTY FIVE MINUTES trying to start that 426. One plug was black, and when we put a spare in, it got WET, but not black. We cleaned it off, and FINALLY it started. Now, when it would start, it would run for mabey a second, then stop, two seconds then stop, three seconds - and so on and so forth, until it finally kept running. I tell you my legs and his legs are still tired.

There is NO excuse for a machine to be THAT hard to start in the year 2000 (bike model year). I don't care if it is 0 degrees.

Anyway...any recommendations to do to it?? I read in a few other posts about mabey richening the air screw a 1/4 - 1/2 turn.

This bike is stock. Stock exhaust, stock jets, stock everything. I have mentioned the grey wire mod, and the BK mod to my dad, but he is in no hurry to do anything to his bike. It as it is, is more than enough for anything either of us could possibly do.

The bike is kept in an enclosed trailer, very clean, and well maintained. It is simply a freakin' bear to start in the cold. Like I said...I kicked over my bike twice, she fired right up. Doens't need the choke after about 20-30 seconds either. It's not like a good starting bike doesn't exist...it does. It's certainly not blue though...how about orange?

Again...what can we do to get it to start easier?

2000 YZ426

Stock jets

Stock exhaust

Original top end

NO modifications to the machine or it's ignition.

Weather - freezing to slightly above or below, humid. (sometimes in the snow even)

Approximately 500'-1000' MSL.

Also...dad bought some ether. We are going to use that in tremendously small amounts if the sucker doesn't fire.



I rode my 2000 YZ426 Saturday (about 10- 15 degrees), started 2nd kick.

I have 168 main jet, EKR needle (stock) clip 3, 45 Pilot jet (48 pj might be better), Fuel screw 1-3/4 turns out. I did BK mod, about 1 second squirt, so I have to twist throttle about 3 times,then kick (1 should be enought for stock)

Hope this helps


My bike is hard to start in the cold too. It also does more popping on decell. I picked up a 45 pj last week so I'm going to try that. Also I have a question, I ordered a WB E sries shorty pipe and I'm wondering if I'll need to re-jet for this too?


I have an FMF Powercore IV pipe and FMF recommended going up 1 jet size on both the pilot and the main. I guess the thought is it can breath easier so you have to feed it more. Don't know if this is applicable for the WB E series or not, but some indication that pipes can impact jetting.

hello,i'm frenchguy.i live in provice of quebec(lac st-jean)the cold temperature i know that.actually -15'c and i have learnd to start my 01 426 with many%%%%%5$$$$$47*****????tabarnac,calisse ,ostie,**** ,chit and many plugs+oil.first,under 10'c put 10w30 oil and under 0'c put 5W30 oil.second,hold the throttle during 2 sec or 5 hit,choke it and kick.it should start and stop.give 2throttle hit and kick.when it start never putoff choke and give some gaz.go ride slowly with choke ,put off it when engine turn good.never stop the engine be very hot because when you restartyou should flood it.in your question you ask about plug and rep.engine stall:that because your oil be full of gaz(you flood it) that do like you try to start it with full throttle.change oil+plug and retry.good luck.my personnal record it's 3times in a day.(i whish that you understand because i'm bad in english and see later in my profile i will send me riding in my track with 3 feet snow)

me no underatandy much very but that's ok I only speak hick... read my jet post it'll blow yer dang mind hehe

Hi I am new to this site and the newer 4 strokes and my 2002 426 is harder than crap to start I have had it since chrismas and fowled three plugs don't know whats wrong today it died and wouldn't start back and I tried the hot start and it would almost start then it would do nothing so I would put the cold choke on and the hot start off and it would almost startthen nothing and it would again almost start with the hot start but then nothing.I am clueless is to what is wrong my dad thinks it is something with the bike and wants to take it back to the dealer but I keep telling him it is probably the jetting or something. does any body have any idea what is wrong it has been under 40degrees the whole time could that be the problem any help would be greatly apreciated I don't want to get rid of that beast. :)

Hey George,

Whenever I first got my 426 over a year ago...it fouled about 5 plugs in 2wks! The bike was a pain in the @$$ to start! The problem was the check valve on the hose that comes off the gas tank (it is a grey piece about 1/2" long). This valve allows air to come into the tank but keeps the vapors from going out. So what would happen is: on the way to the track in the trailer, pressure would build up in the tank and it couldnt escape, so it forced gas into the cylinder, which flooded the bike before I even rode it! After I removed that piece it was easy to start and now it rips! You also might want to turn your fuel screw to 1 3/4 turns out and turn your idle up, this will also ease starting. Check out my website at http://mx393.tripod.com I have alot of tech articles that will help your bike start easier and stuff that will help a beginner (ex: BK mod...which is very popular on this site, just do a search on it) Oh yeah I am also only 16, so you arent the youngest member on this site LOL! Later,


George#116 - yes it is the jetting making it hard to start.

I rode today in 45-50 degree weather with my stock bike and 42 pilot jet. It started on the 2nd kick. You can do it too.

Here is the routine I used today:

(1) adjusted the fuel screw to 2.75 turns out (normal for my bike in 70-80 degree weather is 1.5 turns out),

(2) choke out,

(3) two blips of the throttle,

(4) the normal "drill" (bring to "hard spot" (TDC), with compression release pulled in inch past the hard spot, bring kick start all the way up, then kick it firmly and swiftly all the way through the stroke).

I really should have installed the 45 pilot jet but I didn't.

Good Luck,

Steve T

My P.O.S won't start either. Now its lost compression. At least it's only about 40 deg F here and was mid 40's today (which is perfect temp in my opinion). My scoot ALWAYS starts 1-4 kicks except on a couple of fouled plug occasions. I'm fixing to check the valve clearances and look at the jetting. I'm keepin' an eye on this post.

The little woman's XR200 ran great today so I took turns with her and had a little fun anyway...

well after reading all of these posts here, i now know why my yz400 will not start and keep fouling plugs also. it has all the symptoms that the 426 has when it does start, popping, starts then stops, etc... oh well with average temps around 20 degrees i think its too cold to ride anyways :)


98 yz400

fmf powercore IV, renthal bars, acerbis fuel tank/handguards, devol radiator guards, and new excel rims on the way :D

JohH: I ran into that loss of compression a few months ago on my 426. Like you, the first things that came to my mind was that I had compression leakage due to a snug valve or two. My valves were fine. I started gently kicking the engine through until it suddenly and unexpectedly started. I let it idle for about a minute then shut it off and checked the compression again. It had normal compression. I weigh 185 and could stand on the starter lever at 9am position and it would hold my weight for nearly 5 seconds. Why it lost compression momentarily is a mystery to me. I have an opinion about why this ocurred but have no way of proving it. This has happened to other thumper owners as well so evidently it's just one of those things that happen from time to time.

hey motoman393 it is nice to see another young person riding a 426 every body around here thinks I am crazy. I think they just don't want to be out ran by me.haven't started racing yet but probably will in febuary.

Concerning loss of compression:

I had the same thing happen a couple of times, usually when it was cold out. The first time it felt like just like kicking over my old KX 500 so I gave it a couple of kicks and it fired right up.

Everything returned to normal after the engine warmed up. Since I have started leaving the piston at TDC whenever it is parked in the garage I have not had the loss of compression. I'm no expert but this tells me that if it sits for a week or more with a valve partially open it doesn't seal properly until the engine fires. What do you all think?


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