Possible Plug Fouling - Attn:Norman K.

Norman, I have just pushed my bike back from the third bike related/plug fouling/????? ride in a row. Since I have owned my 01'426 I have went through no less than 20 plugs. I've done the BK mod, I have played with the jetting but like the stock jetting best, and I received a new cdi. The new cdi made my bike run great, it idled, it started, it ran great yet the occasional new plug was needed. The last three rides it hasn't started, it's run like it's really rich, and it is up to it's old tricks again. The most exercise I get is pushing it back home!

Please tell me what you've experienced is the same and you think that you have finally come up with the fix? It has crossed my mind to sell the bike, but when it runs good, I love it.

Thanks, Brady.

I have had the same fouling problems with my YZ 125. Im not sure how much 2 strokes and four strokes have in common fouling plug wise but it has givin me some problems. After cleaning the air filter, cleaning the carb, looking over the choke, and changeing the jet and the needle the problem was better but still wasnt fixed. I put a 1 notch hotter plug and it did the trick. Before i couldnt even idle, i would have to be on the pipe even when i wasnt going, and for what i do, which is mainly ride trails, it is always nice to idle :) . You probably know that when the temperature changes it affects the jetting, and the winter could be making it foul the plugs. If that doesnt work then i have no idea.

Ive ridden my bike twice since removing the wire from the plug, it runs great. Ive had no more fouling problems and the bike starts in one or two kicks hot or cold. It worked for me!! Try it you have nothing to lose, just remove the wire from the connector and ride it, dont cut the wire.


i disconnected the wire today..cant tell any differance yet...im gonn arace this weekend at a x-country..if it dont do any better its for sale and im going back to a 2 smoker

I just put in a new spark plug and disconnected the aqua blue wire from the cdi. It started 2nd kick, it idled very well, and it started 3 times repeatedly. I'm so pumped and have hope now. If it keeps up I'm going to hit up the trails in Michigan for some riding, up till now I couldn't in case it died out there.

Yamaha should sponsor this web site or at least acknowledge it. The help I've received from you guys has been invaluable. Thanks...

Is the issue with the starting when the air temp is say below 40-45degrees ? My YZF & WR hates cold temps, but so do I so I do not ride below 45degrees.

Motoman393 - what does this blue wire do? & why would the starting be affected by unplugging it?

My bike ran like crap and fouled plugs whatever the temp was, no difference.

Other guys I know with 426's (Yz's or Wr's) have had no problems such as this and there bikes have stock jetting, the original plugs and their bikes have run good summer or winter ... it get's cold here.

My bike would refuse to start . I was going through clean plugs every time I wanted to start it . It was stalling , fouling plugs ( It really p#*#ed me off . Every since I unhooked the wire it starts . 10 degrees - 45 degrees, in the shop at 70 degrees . I no longer worry about starting my bike, it always starts . Although I have never ridden this bike when it was warm out as I just purchased it in Feb. 2002 . It was in the crate when I bought it . Started hard ever since . I was wondering why I gave up my 97 CR250 that started everytime . I have ridden it this winter . My buddies and I stud the tires and hop on the river and put on many miles in a day ( at very high speeds ) Any of you doubters out there still dont believe, that's up to you, but I would do the mod if your having problems. There is a large list of threads on Dirt Rider.Net under thumper central that have taken this mod to heart also. check this out . OH and a Huge thanks to Norman For sharing this with us all. You saved my bike from the For sale market. You are the man !!!!

Read this :http://www.dirtrider.net/forums3/showthread.php?threadid=39474

[ March 19, 2002: Message edited by: rvanliere ]

You guys rule the planet !!!! I did this at lunch today and the damn thing started on the second kick! I have a 2000 426 that I bought new last August and all winter long I have kicked myself into a coronary trying to start it. I even did the BK mod and changed the jetting. I can't believe something that simple could work so well.--Thanx much --- Joe


I have a 99 yz4oo that is very hard to start and some days will not start at all. Will removing this blue wire work on a 99 yz400 and where is it at.And what is the BK mod.

Hey I used to foul plugs all the time. Then I found out it was the air filter oil doing it. If its on to thick it would foul a plug. I now take and extra pre oil filter to the track with me if I think I will need it. Also if you oil your filter give it an hour or so to dry and let the fumes go away and that might solve a plug problem. I use maxima FFT in the bottle to oil my filter. I no longer use spray can Oil. welll hope this helps

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