Problem starting 02 426 spark plug fowled

11 replies to this topic
  • kurtsyz426

Posted April 06, 2005 - 03:15 AM


Hey fello thumpers, I have been reading these threads for ages and have finally decided to add one of my own.

I have owned my 2002 yz426 for a year now and over the past few months have found that every now and then (well three time over the past 4 months) I have been experiencing trouble starting her up due to a fouled plug, ie: if it does not start within the first few kicks, I know this is the problem, cos other than that she is as sweet as a nut within the first kick or two. I change the plug and BANG she is thumping away...

When I inspect the old plug, sure enough it is all oily..

Any ideas???? :naughty:

  • westcastler

Posted April 06, 2005 - 12:38 PM


take a glance at the pilot jet, it may be clogged or too rich.

  • mkporn

Posted April 06, 2005 - 03:02 PM


Oily or just wet with gas?

  • sirthumpalot

Posted April 06, 2005 - 04:45 PM


2 things gave me this problem:

1) Gas from a specific local gas station
2) Running it without letting it get up to full temp. i.e. start it and rev it for a buddy, 30sec total run time then turn it off. Presto fouled plug next day

  • Chris_from_Oz

Posted April 07, 2005 - 04:04 AM


2 things gave me this problem:

1) Gas from a specific local gas station
2) Running it without letting it get up to full temp. i.e. start it and rev it for a buddy, 30sec total run time then turn it off. Presto fouled plug next day

Yep, same here. I've copped a couple of bad batches of fuel (contaminated with water), and also a few times in the past i've tried to give it a rev' too soon, before it's warmed up properly, bike's stalled, kick it forever, no go, fouled plug.....
I go totally out of my way now to only go to large petrol stations, that have a high turnover of Premium, and also, use only the most commonly used pumps, not the pump right up the opposite end of the forecourt that nobody uses. I used to run petrol stations in the early '90's, you would be surprised how much water is 'an acceptable amount', according to the fuel companies. In Australia, i've had best results with BP Ultimate, Caltex Gold, and Mobil Synergy 8000. They seem to be the most consistent as far as quality goes.

  • kurtsyz426

Posted April 07, 2005 - 05:57 AM


Come to think of it mkporn, it may have been wet with gas AND oliy. Sirthumpalot may also be onto something here as I have been showing it to the odd mate lately for a gloat (espesh with the new Thunder Alley pipe on it)... i am fairly confident about the gas quality as the local gas station is pretty busy.
Incidently I have also notice with the new TA pipe that is sometimes backfires when I try to start it whereas it never used too with the orignal pipe on it... could these two be related, i.e: oily/wet plug and new TA pipe?

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  • T-Doshi9

Posted April 07, 2005 - 06:36 AM


check the pilotjet!! play with that!!! sounds like its rich!!

  • Jeremiah

Posted April 07, 2005 - 06:46 AM


I had a similar problem when my pet cock gave out. I was getting flooded as gas never stopped leaking into the cylinder. Essentially my carb got clogged, but yet my plugs were always wet and oily. I know this post seems a bit off, and maybe it is, but that was my experience. I cleaned the carb, put in a new pet cock, and have had no problems since.

Feel free to rip away as I know there seem to be contradictory points here.

  • Rappin 608

Posted April 09, 2005 - 08:25 PM


I found this same problem after kicking for a while and it doesn`t seem to have any fire,I pull the plug and put in a new one, it will fire right up. I have been told to
``blip the thottle``. DO NOT DO THIS!!! It will foul a plug everytime!


2001 yz426
2003 xr80
2001 xr50
pocket rocket

  • kurtsyz426

Posted April 10, 2005 - 04:05 AM


Thanks to you all for helping me with this one.

Happy Riding"-))

  • T-Doshi9

Posted April 10, 2005 - 09:23 AM


never never blip the throttle!!!!! do not touch the throttle!!!

  • sirthumpalot

Posted April 10, 2005 - 11:39 AM


Just an FYI: Gas stations of the same brand but in different areas may have different gas, but in my case the Mobil down the street would kill spark plugs for me on a regular basis. The bike would run great all day, but the next day it took a new plug to get any fire (or clean the old plug with carb cleaner often works).

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