Fouling out plugs on a my 450


11 replies to this topic
  • YZRIDER1127

Posted October 25, 2004 - 04:32 PM

#1

Does anyone know why i might be fouling out plugs on my 2004 yz450f. Ive fouled out 2 in the last month. It never happens when im riding its only when i go to start my bike. When i pull the plug its black and wet like it has been flooded but i dont ever give it throttle when its not running and i dont think its running rich.

  • WR426madness

Posted October 25, 2004 - 04:54 PM

#2

What plug are you running? I had the same problem and switched from NGK to Autolite and the problem with fouling plugs went away. NGK has a very pourous insulating material for the insulator around the electrode to help disapate heat, how ever it also makes the plug easier to fuel foul. Also make sure you don't touch the trottle while starting or you will flood the bike for sure. Try starting the bike with out the choke several times, if it won't stay running then use the choke and let it run for no longer than a min. or so with the choke on.

  • 01yz426

Posted October 31, 2004 - 11:27 PM

#3

You know what.... I've been hearing the whole starting problem thing since Yamaha introduced the 4-stroke mxer, and to tell you the truth I haven't the slightest idea why.... And if you are fouling a plug it's usually the riders fault...... You must be lugging it around and puttin her away wet my man...... Let er rip the next time round and you should be good to go for many rides thereafter.....

  • berudd

Posted November 02, 2004 - 10:23 AM

#4

Note that he said it was when starting. I have similar issue with my 426. It always seems to occur after I oil the filter. I really make sure that I soak up the excess oil. I like to roll it up in paper towels a few times for this. Just don't wring it, squeezing is fine. Then when I start it, I make sure that I can let it run for a while. I have noticed that if I fire it up and only let it run for a few seconds, I may fowl the plug with a new filter. So I always let it run on the choke for a few minutes to get warmed up. Not too much trouble since I got this routine down.

The fuel screw could also be to rich. Do you ever heard popping on decel? If you never do, then I would say you are a bit rich on the bottom and I would screw the fuel screw in 1/4 turn and see what happens. I slight pop or two in decel is ok, but if it noticably extreme, you could be too lean.

The advise about not using the throttle is gengerally good with exceptions. I have never fowled a plug from doing this when I should not. I have flooded it but I don't think I have fouled a plug. If the bike is completely cold, as in not run for a day or more, I will pull the choke and give it 2 twists of the throttle to prime it.

  • Geezerx

Posted November 02, 2004 - 10:40 AM

#5

My 03 450 is hard to start only if i do not ride it for a month or more. It will always start, it just takes more kicks. I would suggest that you pay close attention to the starting procedure, is the choke on or off, if you twisted the throttle to squirt some gas in the cylinder, how many twists and were they short twists or long. If the plug is wet it is getting to much fuel.
As far as starting the bike after the air filter is oiled. I oil the filter and have it done a day or two before I know that I am going to change the filter. I had starting problems when I would change the filter just before riding. I learned the hard way with my 98 & 99 YZ400's. Back then you learned throught the school of hard knocks.

  • TheRainMan

Posted November 02, 2004 - 05:21 PM

#6

What autolite number matches NGK CR8E?
:cry:

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  • TheRainMan

Posted November 02, 2004 - 05:21 PM

#7

What autolite number matches NGK CR8E?
:cry:

  • slappie

Posted November 03, 2004 - 08:34 AM

#8

I tried to do the two twist method the other day after not starting my bike for a week.

It started first kick and then died after about 3 seconds. I also had the choke on. Fouled out the plug and I was kicking for a frickin' hour.

Put a new plug in and started right away. The old one was black, wet and nasty.

I will never touch the throttle when starting again, no matter what!!!

  • PumpkinHumper

Posted November 03, 2004 - 09:25 AM

#9

Does anyone know why i might be fouling out plugs on my 2004 yz450f. Ive fouled out 2 in the last month. It never happens when im riding its only when i go to start my bike. When i pull the plug its black and wet like it has been flooded but i dont ever give it throttle when its not running and i dont think its running rich.


What kind of temps are you riding in right now. In colder weather I have found that I need a larger starter jet to get her fired. The starter jet only works with the Choke circuit. In cold weather the choke circuit runs lean. The bigger jet helps. Ever notice how it starts and stalls like 10 times simetimes before you keep it running? that is the starter jet causing that. Might be worth a look see.

And yes it can cause a fowled plug from running lean. I dont understand how. I was killing plugs left and right last winter (20 deg weather) I went bigger on the jetting and it was tons better.

  • MXof21

Posted November 03, 2004 - 10:05 AM

#10

When the weather is cool I give my 03 2 twists and give it a kick. It starts, sputters and dies, I give it one more twist and one more kick and it always starts. I never give it any gas during the kick, just a little primer before.

  • slappie

Posted November 03, 2004 - 12:53 PM

#11

Man, that is scary.

If I did that to mine I'd be kicking for a frickin' week.

  • MXof21

Posted November 03, 2004 - 04:54 PM

#12

I had an 02 YZ250F and if you looked at the throttle the bike would not start. I could not get my 03 YZ450F to start and a friend suggested giving the throttle a couple of twists and I thought he was nuts. Nuts or not the bike starts second kick as described above regardless of weather.





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