Yzf Keeps Fouling Plugs

[MTRSPORTDAN]

I have a 01 426 that keeps fouling plugs. It all happened a couple of months ago. I put the bike away for the summer and one night decided to start it up and got nothing. I replaced the plug and it fired right up. It sat for another month and I just tried to fire it up and the same thing as before. Has anyone else had this problem of going through plugs when not using the bike? Any help is appreciated. Thanks, Dan

[642MX]

Sounds like stale gas is fouling the plug. Have you drained the tank and carb and replaced with fresh fuel?

[MTRSPORTDAN]

I will try some new gas but do you think I should try to clean the plug or just get a new one. The plug only has about 5 minutes on it?

[642MX]

I would replace it, they don't cost that much.

[MTRSPORTDAN]

Thanks for the help, Dan

[Satch0922]

since it has been sitting around with gas in it I think it would be a good idea to drain all the old gas, clean the carb and then install a new plug and fresh fuel.

[new2blu]

I had the exact same problem with my 04 YZ450F. I had to kick mine 50 or so times and it would stumble then die--this is what I did to fix the problem.

I tried: 1. new gas--no change

2. new plug ---ran ok for a day then problem came back

3. new plug again--same problem

4. shimmed valves--- starts 2nd-3rd kick every time

[Fastest1]

I also used to have this problem on an 00, the thing that helped the most was turning off the petcock while it was running and let it run til it dies. It eliminated the problem for me.

[SureBlue]

I can't say an iridium plug cannot be fouled, but I never did foul one. CR8EIX

[MTRSPORTDAN]

Thanks for all the help.

[913YZ426MXer]

Danny Boy,

#1. When you start your ride let it run for awhile.....meaning let the engine get to temp prior to killing it. (Reason being that if you don't let it get to temp the up burned carbon residue will build up on the plug, fouling it!)

#2. After getting to temp (after riding session, etc....) while the bike is running kill the fuel feed......let it burn off all the gas in the carb.

My '01 had the same problems. Once I follow the suggested steps I have yet to foul a plug! 1-2 kicks to BRAAAAAAAAAAAP!

Good luck!

[Flash319]

I agree with the first part but disagree with running the carb dry. If you run it dry then the next time to go to start it you with have to kick a bit more. Then the patience kick in and you grab a bit of throttle and BAM flooded. I never touch the throttle anytime during starting and have no problems.

[jamieyz426f01]

Definately let her warm up(feel the head it will be warm..duh!), i also am not to sure about running the carb dry. when i have to leave mine for a long period i lay it on the floor to drain the fuel the lazy way,when it isnt coming out of your overflow pipe pick her up but with the petcock in the OFF posistion kick it through on the decomp about 5-10 times(how ever many you can be bothered), then turn the petcock into the ON posision kick it through with the decomp on again(about 5-6 times) and then give her a good kick. Works every time for me

[913YZ426MXer]

I agree with the first part but disagree with running the carb dry. If you run it dry then the next time to go to start it you with have to kick a bit more. Then the patience kick in and you grab a bit of throttle and BAM flooded. I never touch the throttle anytime during starting and have no problems.

Reason for running dry is due to the down time between rides. If someone sits the bike for months on end running the gas out is best. Though touching the throttle on 426 is a sin. If the system is dry a mild twist (1/4 turn) of the throttle prior starting would not hurt.

Cheers.

[MTRSPORTDAN]

I will try it out and let you guys know. Thanks, Dan

[creek freak]

Keeps happening to mine too. Seems premium fuel will only keep for about three weeks in the tank before the fuel gets stale. Seems to be a normal condition as I asked the dealer about it. Guess the high compression is just picky that way. NEVER leave the carb dry in storage. Good way to ruin the needle and seat. Over the winter I put in fuel stabilizer so the carb does'nt gunk up. I've never seen a 4 stroke foul a plug due to running it hard cold like a 2 stroke. If you're having the same problems as me you wont even get it started before the plug is fouled. BTW, mine is sitting in storage right now with a fouled plug from last time I tried to start it to load it in the truck ( it had sat for over a month ). I always keep a spare plug handy along with the factory plug socket that makes the swap much easier.

[SureBlue]

I've never seen a 4 stroke foul a plug due to running it hard cold like a 2 stroke.

Never warm up a 4-stroke like a 2-stroke. Let it idle and give no gas untill it is warm. Worst thing (after running without oil) is that you rev up the engine, since the piston warms up and expands faster than the cylinder, the piston may crack. Only FOOLS rev up their 4-strokes after cold start.

[creek freak]

Running ANY engine cold is probably the stupidest thing you can do. I THOUGHT that would have went without saying. As a certified mechanic I've seen numerous cold start failures. I always start my bike and let it run while I gear up. Also never stress a cold chain. Let it warm up on a small ride before you load it up. It's suprising how warm a chain and sprockets get. You'll get way less stretch if you warm it up. BTW I'm curious what you mean by never warm up a 4 stroke like a 2 stroke. I've seen a lot more 2 strokes cold seize due to throttle input, also more cracked piston skirts.

[SureBlue]

BTW I'm curious what you mean by never warm up a 4 stroke like a 2 stroke. I've seen a lot more 2 strokes cold seize due to throttle input, also more cracked piston skirts.

I do not know about your certification, but 2-strokes cannot be let idling while you gear up, they need careful pumping for lubrication also when cold.

[creek freak]

I do not know about your certification, but 2-strokes cannot be let idling while you gear up, they need careful pumping for lubrication also when cold.

No, no. Your taking my statement wrong . Yes, 2 strokes require "pumping", but there is a difference between getting on a bike with a cold engine and putting the engine under load, or playing with the throttle during warm up. And yes, my bike is a four stroke and I have the luxury of letting it idle while I gear up. When I refered to "never running and engine cold" I should have worded it "never putting a cold engine under load". Just common sence.