Fouled plugs = foul mouth!
Posted December 28, 2000 - 07:58 PM
But really, I've already posted that my '01 suffers the same problem of fouling plugs. Jetting changes have no effect.
It's NOT the air filter. Yes, I'm familiar with the problem of trying to start the bike with a freshly-oiled filter but I've use thrououghly dried filters and the problem persists. These are the same filters I used on my '00 426 with no problems.
I've been more observant about the bikes behavior and have noticed a few things:
1) the bike starts fine (new plug), idles great and initially runs cleanly,
2) after, say, 5-10 minutes of running (varies depending on temperature) the bike goes through a phase that involves missing/backfiring/popping and the idle speed drops so that it's necessary to constantly blip the throttle in turns,
3) after another ~10 minutes (if the plug doesn't foul) the bike starts to run better as if the mixture has leaned out to normal levels,
4) the bike will now run properly (or almost considering the almost-fouled plug) for the rest of the day - unless you stop and take a break,
5) after the break, upon restarting the bike it will go through the same period of poor running/popping/backfiring and poor idle and then clear up again (provided the plug still works).
I thought that the answer might be the temperature/temperature distribution of the carb due to a misassembly/machining error but now, after reading about how a replacement carb started suffering the same problem after everything was fine for a while, I don't know. Also, I seem to remember that the first ride (during break in) didn't go through the poor running phase.
But if it's not the carb then how did a replacement 'cure' the problem for time? This is getting very strange. In my garage I have my '00 426 which has always run fine. I'm wondering if I should try swapping carbs/cdis between bikes. I know there have been a number of changes including spark advance so I don't know if I'll learn anything.
Posted December 29, 2000 - 01:51 PM
i think rob c is very close. now i've had the problem & cured it (unfortunately i did 4 jobs at once so i'm not sure)i'm convinced tha some passages are very susceptable to muck.
i found the pillbox slit grimy, it shouldn't be grimy!
Posted January 01, 2001 - 10:14 PM
Posted January 02, 2001 - 02:46 AM
any other transport would have a tan coloured plug wouldn't it? it would be nice to talk to a plug guru.
i bet the top gp lads don't have this problem, i bet they had a hush-hush circular come round & they've been laughing at us ever since.
has anyone had all this set up on the rolling road/dyno?
i run a 45 pilot on my WR here in the UK & i 'only' have a 162 main jet. i've backed the acc PJ off as much as i dare.
when roadracers start to run out of battery power on their total loss ignition bikes, the plugs start to foul!
just some idea's.
Posted January 02, 2001 - 12:56 PM
Posted January 02, 2001 - 03:36 PM
Posted January 02, 2001 - 07:37 PM
plug-fouling Y2K.1 YZ426 in Colorado.
Great info and I'll go get registered as
soon as I post this.. but to the point;
Mine's doing the same thing except it
runs fine all day on the same plug. Will
NOT start the next day on the same plug.
I'd hoped jetting was the answer but right
now I'm being skeptical. I'll contact the
dealer tomorrow (Apex, Colo Spgs) to see
if they've gotten any updates. Thanks to
all for the posts.
Posted January 03, 2001 - 07:49 AM
TMX AND MY DOGS BITE!!!!!!!!!!!!!!
Posted January 03, 2001 - 08:16 AM
Posted January 03, 2001 - 11:59 AM
the generator output
the coil output
this is the first bike i've ridden that backfires on a closed throttle. my only other experience of this is with bikes that had leaky exhaust manifolds.
but the backfiring isn't leaky exhaust. is it ignition timing on the closed throttle?
both the wr & yz suffer so i think the generator output can be dismissed.
so carb, black box, coil & lead. that's it.
Posted January 03, 2001 - 08:28 PM
Posted January 04, 2001 - 09:06 AM
My question to you guys is:
Do any of you get a nice brown plug on your 426? If so, what is your elevation and jetting? I have yet to talk to anyone who gets a brown plug at elevation.
Posted January 04, 2001 - 10:37 PM
I have a stock 01 426. Ive fouled the plug once during start-up( I gave the bike a little too much throttle right after the bike turned over and it died. After about 20 more attempts to start it, I checked the plug and it was covered with carbon and wet). I sand blasted the plug, put it back in the bike and it fired up on the 1st attempt. Other then that one time, the bike runs great and the plug is usually black, but not carbon covered. Its in the 20's here, sea level, and I havent messed with the carb at all. Sorry to hear about all your troubles. Is there any kind of lemon law that might cover you? In New Jersey if a motor vehicle dealer cant fix the same problem in (3) attempts you can get your money back or another new vehicle-maybe a dirtbike would be covered by the same law. If I had an unresolved problem with my bike, I would get a replacement or the dealer would mysteriously burn to the ground. Thats a bunch of **** -for 6000.00 a bike should run for more than a few hours! Good luck.
Posted January 04, 2001 - 01:39 PM
"A friend of mine just bought a brand new wr400 99 model ex showroom stock and it run fine for two weeks and then started fouling plugs every time he rode it.I gave him a hand with his jetting because his bike is the same as mine and we ride in the same areas and my bike is o.k .Rejetting did not help the problem, then someone said what about the C.D.I so he had the bike shop check it with a multi meter and it checked out fine. Still not happy he swapped the C.D.I with another bike and the bike run great so he had it replace under warranty and his bike hasn't had a problem fouling plugs since.
I never thought this would have been the problem but I rode the bike just before and just after the C.D.I was changed and what a difference.
Not an expert just my 2 cents worth."
Definitely food for thought...
P.S. bibainb my bike does exactly as you describe above.
Posted January 04, 2001 - 01:46 PM
4,500 ft. +, moderate temps (So. NM)
OBEKP # 4
I think your dealer is either an idiot or is convinced that you are. From what I have read of your posts I’d bet the ranch it ain’t your acc. pump. I’d bet the north forty it ain’t your carb at all.
The air passages they are talking about must be the air jets on the back of the carb, I think I mentioned that it sounded like yours (or was it the guy in Albuquerque?) might be clogged. Rotating the carb is silly, the air filter joint, which covers the air jets, moves with the carb and the passages in the joint sit inside the airbox boot regardless of their relative (boot & joint) position. The passage in the joint that feeds these jets is relatively large, I don’t see how it could get totally pinched off (and that is what it would take).
It must be ignition related. I don’t have your patience, I’d have tried the CDI swap already and to hell with the dealer.
Keep the updates coming, I wanna know how this thing turns out (probably with your dealer looking foolish and hopefully with you riding a well-running bike). When they discover how stupid they have been, don’t rub it in (not that I wouldn’t). Be gracious and they may reward you for your trouble (and to help get over their embarrassment).
BTW, totally different bike, but I had a ’95 KX 250 that fouled a lot of plugs, despite a ridiculously lean pilot jet. I swapped the CDI from a friend’s bike at the suggestion of another friend and that was that. I coughed up the $ for the new CDI, another friend still has this bike and it still hasn’t fouled any plugs. I never figured out why it was doing it to begin with, all I know is it was obviously the CDI.
I believe you mentioned that your bike ran perfect at times but continued its problems at other times. Supposing the CDI is the culprit, whatever it is doing it is intermittent enough that your dealer hasn’t encountered the problem when testing it.
Maybe you should coyly suggest this possibility to them in the hopes that they will allow a swap. At this point they should do whatever you say, IMO.
[This message has been edited by Hick (edited 01-04-2001).]
Posted January 04, 2001 - 02:18 PM
nobody has picked up on this low generator/coil output (don't forget it still leaves the lead & cap!) causing the sootiness. as i said this is how roadracers run just before they've had it. although to be fair they misfire at top revs first.
Posted January 05, 2001 - 10:38 PM
Posted January 05, 2001 - 02:20 PM
Posted January 05, 2001 - 07:53 PM
Today, in Albuquerque, NM, it was 54 F (the warmest I've ridden in) and I took the '01 out for a spin. It ran the best it has since I picked it up on 11/11 (that, BTW, is the start if Fasching - a german holiday that runs until February or some such and, no, that is not short for fascist it's more like Halloween but they actually charge money to watch the small parades that every town puts on). Sorry, way OT. Anyway, the bike ran better at 54F than at colder temperatures with only a much reduced period of running 'fat'.
The CDI eh? I almost swapped the '00 to the '01 but as I stood there, ratchet in hand, I couldn't think of a single reason as to why that could be the case. The problem is intermittent, seems to be temperature dependent and when I tried applying a hot air gun (not too hot!) on both the carb and CDI I couldn't get any response. Still, based on some of the other remarks in this thread I may have to give it a try.
Posted January 06, 2001 - 05:38 AM
I will be a happy camper when someone figures this problem out.
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