Plugs, plugs, plugs,more plugs

Okay guys, here goes. Convince me I shouldn't sell this thing.

I've been going through plugs like every ride now. My problems began awhile ago when I swamped it in a large water crossing. The thing was missing bad in third and worked it's way down to second, then 1st. Changed plug and all was well, or so I thought.

I've purchased and installed a stock US pipe (I had Canadian version, no spark arrestor). The Yamaha wrench said it needed to breath better so he removed the airbox lid and uncorked it. He also moved the pilot screw to 7/8 out. CDN stock is 7/8. He said stock was "about 2 turns". Thing ran worse once I was out in the ORV park. I put the cork back in and it ran better. It still misses in the midrange, sputters at times and most of the time the front end won't even come up in 2nd gear. :)

Yamaha wrench put an Ohm meter on the electrical and the second source coil is coming in at about 50 ohms. Should be around 460ish to 690ish at ohm X 10. Contacted Blackfoot Motorsports (where purchased) and they say "sorry it's a race bike, can't help you". I ask if Yamaha will "good will" the $200 part since I know I didn't break then thing and they say "sorry, no good will". Huh?

Sorry about ranting, I'm about at my wits end. My friend said, "oh, you'll become a mechanic". Boy, was he right.

Source Coil #2. Will a low ohm reading be causing the reduction in power and the fouling of plugs. I'm guessing that it's not signalling the plug to fire at the appropriate rate and flooding the bike, hence, black wet plugs.

Anyone had experience with this?? I just would like to feel more comfortable about spending the $200 for a new source coil before I do.

Thanks for any input.


The fact that your coil show onls 50 ohms instead can be the consequence of a short circuit in your coil. Which means that the coil can't load enough energy to create a decent spark.

First at all Clean the carb ! Check the resistance of the coil again, if your results don't macht the imposed range, i think this could indeed be the cause of your plug foulings.

If you change your exhaust system you maybe chould check you carbsettings.




'99 WR400 F, YZ exhaust, throttle stop trimmed, WR timing, airbox cover removed

Cleaning the carb?? Not sure if that will affect the ohm reading.

arrrrgh! anyone want a good deal on an 01 wr426.

I did not mean cleaning the carb would change the resistance of the coil. :)


So yust check the resistance again

50 ohms = short circuit = no good = change

You're welcome.


'99 WR400 F, YZ exhaust, throttle stop trimmed, WR timing, airbox cover removed

[This message has been edited by Ynahg (edited 05-08-2001).]


Your ignition may have problems, but so may the carb. Flooding in deep water can raise havoc. There are air jets on the intake side to clean, a pump diaphram that should be cleaned top and bottom, and float bowl removed and cleaned. Maybe the pilot jet too, while the bowl is off. If you don't want to do it, take it to a shop and pay the price to get it right. ($$$ :) ouch!)



Thank you for your suggestion. I misunderstood your comment about the coil relation to the carb. My response was not intended to be sarcastic, but rather may reflect my frustration level with regards to my current problems. I appreciate your input and will try cleaning the entire carb.

I've learned since yesterday that Canada has no warranty on this bike, or at least is disinterested in good willing the part. Neither Yamaha of Canada or U.S. will accept responsibility for a defective product. I will never purchase another bike cross border and I caution those considering doing so.

No problem, Mojo, i think you just need some riding



'99 WR400 F, YZ exhaust, throttle stop trimmed, WR timing, airbox cover removed

I've never fouled a plug on my 99 dbr. I recently changed it because its been so long since i purchased the bike. The plug looks good still, this bike has been real reliable for me ,starts easy. best bike i've ever owned.


Mojo, I don't know what the problem with your bike is but I wouldn't give up on it. Its probably some stupid little annoying bug that will get fixed. When it is, you will love your bike. My WR has been and is great. Last week I started it after at least a week of not running it to warm it up to change oil. It came to life after the second kick but when it did it seemed to be idling really low. Then I realized that I forgot to full the choke on. A good running WR is an amazing motorcycle. Get yours fixed you won't be dissappointed. Good Luck!

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