Starting Problems WR426F, advice needed

Hello all, great site you've got here. I've been reading it for some time now but this is my first post.

I'll preface this post by saying even though I'm mechanically inclined (long time wrench on my cars/Jeep) I know jack about carburators, jetting, and dirt bikes.

About 3 months ago I bought my first bike ever, a 2001 WR426F. It had about 850 miles on it, and had been for the most part parked for the past couple years unridden. No problems starting it at first, once I was taught the procedure (I'll add that the bike was warm when I went to look at it, and it has never had any problems starting once warm.)

Went for an all day ride later that week no issues. Came home and washed the bike, tried to start it no dice (yes I'm a noob, didn't take precautions before running a hose over it.) Followed the official Yamaha procedure for about an hour. Eventually I pulled the spark plug, which looked very black and also was wet (appeared to be water.) I threw a new gapped .30 plug in and after some kicking it fired up again.

At that point I chocked up the whole experience to learing and figured I'd be fine. Took the bike out next weekend, could not start it to save my life. At this point I was frustrated and figured I needed some help. Took the bike the the local Yamaha dealer (Colorado Powersports in Boulder, CO) and after a $200 bill they handed it back to me as a bike that started fine with the explanation that it needed a new plug and was re-jetted. They spent a lot of time on it, which leads me to believe they never found the real issue.

For the next week, every day I would start it and warm it up and had zero issues. I did a couple more rides, no problems at all. Went to fire it up again this week (had ridden just a few days ago) and the bastard won't start! Pulled the plug and it is all black and coated with a sticky oil like substance. Threw in a new plug, sounds like it wants to fire now but just won't get going.

The bike as far as I know is stock with the following exceptions:

-Air box cover removed

-Exhaust baffle removed

-Aftermarket lighting switch kit to allow for low/high beam

The gas is 105 octane that the guy gave me with the bike, is a couple years old he told me at that octane the shelf life is almost infinit (is this true?)

He maintained the bike very well from what I can tell, changed the oil every 100 miles etc...had a professional mechanic look at it once a year, gave me the reciepts

I'll also add that while warming up it will die if you give it too much throttle, it pops on deceleration, and if left idling for too long will overheat (10+ minutes, not a good idea anyhow.)

Sorry for long post, is there anything I can try on my own or should I just find a good mechanic?




Couple year old gas? I'd dump that and start over with fresh.

If my bike has been sitting, I will pull the choke, turn gas on, twist throttle two or three times, and she ALWAYS starts on first kick.

If it was run more recently (last day), then I won't touch the throttle. Still starts first kick.

Dump all the gas in the tank, carb, and the can and go get some high octane pump gas at the local fill-em-up station. Bad gas will ruin you every time.

Check the air filter!,it maybe over oiled?,this may explain why the the plug is fouling and the oily plug symptom,if this is the case you may well have to clean out the carb too,if the plug is black and sooty it is to rich,this may be from pilot circut jetting or an oily filter!,either way you will have trouble starting after a while if this is the case?,so i would also recomend new gas,fresh filter,and a new plug(an almost fouled plug will give you no end of trouble!)then run it and pull the plug out after you been out ridin and see how it looks if the insulator has gone all black again it`s time to sort the jetting out!,once you do this you will beable to start the bike with no trouble at all!,a hard starting wr is more often than not caused by jetting!,and welcome to tt :cry:

I'll replace the gas, after draining the fuel tank what's the best way to clear out the carberator and any remaining fuel?

Edit: I'll clean and re-oil the air filter as well, come to think of it the thing is practically dripping with sticky oil. What oil do you use?




Just open the drain screw on the bottom of the carb(the allen bolt with pipe below it)and turn the gas on and let it run through the carb for about 30seconds should be ok :cry:

dripping oily filter

oil level too high?

cam breather hose connected to airbox?

excess oil burning with fuel clogging the spark

clean filter with gas, dry it, lube it with filter oil, remove excess oil by squeezing the gut out of it, but no twisting!!

filter spray is a bit faster applicable

remember that to start this bike, you are always better to start with a lean procedure going richer than the opposite.

giving one or two kick on the hot start while the bike doesn't need it is not very compromising... if on the opposite you try to start your bike with the choke on and throttle twists while it does not need it,then you put yourself into trouble...

that said, it might not solve your problem entirely but at least, I hope it will make you more confident about your drill

Dump the old gas as already stated. Use premium pump gas, not race fuel.

Clean and oil the filter, wrap it in a rag and squeeze out the excess filter oil. I use No-Toil products with no problems. I like the water clean up. I used to use kerosene to clean my filters.

Change the plug often, about every 10-12 rides. If it becomes hard to start, pull the plug. The WRF manual says the plug can become charred even when new if a lot of low speed low rpm riding is done.

Most of all don't give it any gas if you can help it when it's cold. Sounds like your bike is running rich like mine so go easy on the throttle at start up. If it floods, pin the throttle open, pull the decomp lever in and kick about 10-15 times. Then retry the standard starting drill. Usually works clear the cylinder and get it to fire.


Went out and and tried to start it 24 hours later, started first kick! :cry:

Rode around the block a few times, tried to start it again next day, couldn't to save my life.

So today:

-Drained tank, replaced with pump 92 Octane gas

-Ran out about 30 seconds worth into a bucket

-Cleaned air filter and applied new Yam filter oil

-Replaced plug (using NGK 7R I think?)

It really wants to start now, but just won't. The firt kick it turns over a few times then dies. Subsequent kicks result in pretty much nothing. If you kick it about 10+ times with decomp. lever pulled then try again it does the same thing. Finally got tired of kicking and rolled it down my driveway and popped the clutch, started right up.

Somehow I think by the time this is worked out I will know everything there is to know about a WR, which is a good thing I guess. I'd just rather spend more time riding it than fixing it.



-Replaced plug (using NGK 7R I think?)

It should be an NGK CR8E

I think of a Honda "CR80" (CR8E) :goofy:to help me remember this.

Yeah,no need to try a#7,stick with the cr8e,you sure you not giving it a little twist on the throttle as you kick it?,i have seen many who swear they don`t twist it as they kick it over,but when you watch how they do it,as sure as a bear [@#$%&*!]`s in the wood they give it that tiny little bit of throttle as they kick! :cry:,try holding the throlle off and pull the front brake lever on tight so you cant twist the grip as you kick it!,and when it does fire up do not be tempted to give it a handfull rite away,just leave it to see what it does,remember these bikes have a pumper carb(gives it a shot of gas when you twist it)and they will flood the motor if you start tryin to rev it up straight away when cold,just bring the reves up slow with a tiny amount of steady throttle no revin or it will die! :cry:

looks to me the bike floods itself. The bike fires up, just can't keep running with the juice that comes from the carb...I'm no pro at jetting but I would bring this bike back to stock jetting and see what it does. Than modify according to where you ride with the help of a TT guru.

I recently bought an 01 426 used also. The dealer had to replace the black fouled spark plug so I could test ride it. It started first kick no problem, ran fine until I had about a half our riding time on it at home and wouldn't start. The spark plug was fouled black. With some help from my meter, I found out the previous owner had been rough with the spark plug cap and broke the porcelain and most of the wire. Replaced that and it has run like a raped ape since!! :cry:

I keep my right hand on the hand gaurd to be sure not to touch the throttle. Flooding could be a possibility. Also the idle seems low, I'll check that.

btw started fine yesterday, hopefully I won't be facing another foulled plug a week from now.




Yeah i sure hope you can get it sorted out without too much hassle!,best way to check if you gonna have another plug foul up on you,is to just take it out and see if it`s all black again and if it is?,then it`s gonna give you trouble after a short time,i sugest you pull the carb and strip and clean it,and check the float hight!,also take a note of what jets are in there,pilotjet,pilot air jet,mainjet,main air jet,needle code number and clip#,also how many turns out the fuelscrew is set at(make sure you count how many turns it takes to lighly seat it turning it in?)then post it back up,and i`m sure that before long it will be runnin like it should,and if you can do the work your self,it will help you understand the bike alot better!,but you have now arrived at the #1 place to get it sorted :cry:

Had similar problem!


My soultion

1. Don't twist throttle @ all

2. Pull decompression and kick through about 10 times to clear fuel.

3. No choke (If your having this problem)

The sucker kicks over on the first or second try.

Good luck

If you have old fuel in the tank, dump it! Fill with fresh 91 octane. When you start up the bike shut off the choke as soon as possible (don't leave on more than 15-30 seconds)and just set the idle speed up 'till she warms up. If you're in the garage or at car wash and you can't/don't ride the machine for 5-10 minutes then let her sit and idle 'till she's ready to blow steam out of the radiator. If you shut the engine of without letting it completely warm up you are guaranteed to have a fouled plug the next time you try to start.

Matt, sorry you're having so many problems with your bike. Having the bike sit for so long is good and bad. I'm not sure where you are with the bike now but I feel the oil on the plug could be from a oily filter, and if the plug is oily just imagine what your carb looks like inside. I have no idea what the dealer did to your bike but if you know a bit about mechanics I would take your carb off your bike and look at it. You need to learn this anyway for the future, take it out of the bike and clean it with carb cleaner, making sure that you take out all the jets and blow them out, clean the manual pump in the carb and it's diaphram, make sure you put the slide plate on correctly too. Once you know for sure that the carb is spotless drain every last drop of gas out of your bike, not 30 seconds worth but all of it... Then, take the petcock off the bike and clean it out completely, while you have the petcock off do yourself a favor and install an inline fuel filter (now I sound like my father) they cost maybe a buck and can save you bigtime. While you have the tank off it can't hurt you to put in a new plug. CR8e.... Make sure that your tank is getting vented, look at the gascap and the vent hose (make sure the vent hose valve is on correctly.. Also, make sure that the rubber boots going to the carb are tight....

If you do all of these things and it still gives you problems....... Unplug the TPS connector coming out of the carb, (it's that grey connector coming out of your carb, see what happeneds....

Dan :cry:

It sounds like you may have the starting thing figured out. All of these guys gave you good advice and it sounds like it worked. Sometimes you just have to eliminate ALL of the possible problems which I'm sure you have if you followed all this advice. I don't agree that you need to change your plug every 10 rides, I didn't change the plug the whole time I had my 426 and have changed it once on my 450. Bad gas was the issue IMHO. And if it sat in the bike for a long time you may have to remove the carb and completely clean it and blow it out. I had a really tough time starting my 426 when I first got it and it's just a matter of getting the drill down. NO throttle is the # 1 rule. When mine flooded I cleared it by kicking it over with the compression release in AND the throttle wide open about ten times or until it backfires. At that time try it again with no throttle and it should fire right up. In really extreme cases do the same thing with the gas turned off.. I hope this helps!! Big Jim :cry: :cry:

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