spark plug fouling when cold

2 replies to this topic
  • sirthumpalot

Posted August 24, 2001 - 03:36 PM


I Just fouled my second plug and the only thing that I can contribute it to is starting the bike (to show a friend :) ) and letting it run for only about 30 seconds and turning it off without ever fully warming up. The next time I tried to start it, no fire. Not even a sputter. Put in a new plug and it fired right up. Never fouled one while it was running (yet). Has anyone else seen this particular problem? This is an '01 and otherwise has run flawlessly.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • jaybird67k

Posted August 24, 2001 - 04:52 PM


If it is only fouling on start up, then pull the header and look for a carbon build up in your ehaust port and in the header it self.
I had the same problem with a new 01 426 and jetting did not help, but after explaining my problem to BK(Tim Ferries engine mech)he said this is a classic example of carbon build up which holds moisture in the cylinder causing the plug to short out.
He suggested running race fuel, and since I did I have been on the same plug every since.
# 67

  • sirthumpalot

Posted August 24, 2001 - 04:59 PM


It must have been shorting because after I put a new plug in it I hit the old plug with some throttle body cleaner that I had in the garage (spray can) and then put it in the plug cap for an old yz80 that I have in the garage and it got a nice blue spark. I haven't tried it in the 426 yet but I'm wondering if this is all that is needed to save a plug?

I'm going to try to avoid removing the header if I don't have to for sake of time (I don't have much to spare these days). If it keeps doing this then I guess I will pull the header and check, but the bike has so few hours on it that I cannot believe that there would be a significant amount of carbon in there yet (still on the stock chain!). Thanks for the tip though. :)

Related Content


James Stewart back on a YZ450F by YamaLink

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  47 replies

The "going back to the other darkside" adventure... by Monk

Dirt Bike   Make / Model Specific   KTM   250/350/450/505 SX-F & XC-F (4-Strokes)
  • Hot  113 replies

BIGBORE FOR YZ450F 2006? by Taattie94

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies

Megabomb Fitment by 288yz450

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 1 reply

Snake pit oct 30th by The Anvil

Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.