cold weather - rich plug?

I need a little advice about plug fouling.

I have had my bike since it was new in 99 and it has never missed a beat.

Recently the weather has chilled down a bit and all the sudden my bike starts fouling plugs.

Heres the situation:

Went to a race this weekend, the temp was around 50 deg. at the time I was getting ready to turn the bike over. I went through the normal starting procedure and everything acted normal untill the bike lit with the choke on.

Normally when it is cold out I leave the choke on for about 30 sec and I can turn the choke of and it will idle fine, but not this time. This time when I flipped the choke off it died on me. So I started again, flipped the choke off, and it died again. The next time I tried to sart it, it wouldnt light.

After cranking on it for several minutes I pulled the tank, pulled the plug and it was pretty black and oily. So I popped in a new plug, put the whole thing back together and kicked again and it wouldnt light. So back off with the tank and seat, pulled the plug again and it was wet with gas. (thought that was peculiar) Dried it off, put it back in again and the bike fired on the 4th or 5th kick and ran fine all day.

Now, tonight I took it to the car wash and tried to fire it up after washing it and the same thing again. Fired it up with the choke on, turned the choke off and it died again and woulnt start again so I assume the plug is fouled again.

So my question is: Is it the cold weather that may be causing this because it ran and started fine after it was warmed up during the race or is it possible some of my jetting could be off?

I have been running the same jetting specs since I have had the bike and have had no problems in the past winters.

Any help on this matter would be great. Thanks!

Dude....Good to see you're still out there.

I'm going to give you the best answer I can based on what information you have provided. Please bear with me as I know that you are well aware of some of this, but we may have new owners that are not.

Hmmmmm...Lets take a look at the symptoms here. What has changed? Nothing on the bike....Just the OAT (Outside Air Temp) You didn't mention weather or not you have removed the ACV (Air Cut Valve)(De-Octapussed) so I'll work 2 senario's for you.

Senario#1 : (De-Octapussed) Without the ACV the stock SJ (Starter Jet) is way too rich to begin with. It should be reduced to atleast a 65 so that it doesn't drench the plug with fuel (I'll explain below) What I have found normally is that when the fire is lit it will continue to burn unless there is a major change in the three itmes a fire needs to burn (Spark/Fuel & Air) If the SJ is throwing the fuel to the fire and you transition quickly from the SJ to the PJ (Pushing in the Choke button)there will either be more fuel or less fuel thrown on the fire which could cause enough of an imbalance to extinguish the blaze. Without an ACV to regulate the fuel and air flow while on the bottom, you must manually re-jet to match the conditions. First, I have found that without the ACV that the 65 SJ is a good all weather jet for the choke(Thanks Bill), additionally going down one step on the pilot when temps are below 50 degrees counteracts the fuels metabolic compression and decompression when moving through the system causing a fuel overload, thus fouling.

Senario #2: ACV connected. Check for an air leak at each hose connection in the ACV. an Air leak will cause the ACV to artificially richen the mixture. If there is no leak check the float for free operation. If all this is good, consider an ACV failure. If the ACV has failed then manually re-jet as described, or replace the ACV.

New Folks: The ACV is a device used to regulate the fuel/air mixtures on the bottom end as an emmissions control device. While it does the job for which it was intended, it is not efficient and manually jetting the system yeilds more power and better response on the low end.

Hope some of this helps....

Bonzai :)

Well, actually Mr. Yamakaze, I haven't touched the carb. It sits exactly as when I got it new. No BK mods, no ACV removal, no de-octopussing, not even messed with putting a hot start on it.

I have however re-jetted it to high altituide climates and then put everything back once to sea level, but it has ran flawlessley since. (that was over a year and a half ago)

So, do you think even without an ACV removal I still need to go down one size on my pilot jet?

I have not checked for air leaks or float failure yet, but I intend to do so tonight if time permits.

Thanks for the response and I will post back here when I check it out....


Yep.....If you find no air leak, then it can mean only 1 of two things, the ACV has Crapped out..(lots of black smoke if you rev with the choke on) in which case it would be cheaper to remove the ACV and replace the SJ with a 65. and come down 1 on the PJ.

If the ACV is ok...then the culprit is the PJ. Come down 1 and you should be fine.

Bonzai :)

Well Yama,

I got out there tonight and pulled the plug expecting to see it black and much to my suprise it looked jetted right on. So I slapped it back in and it fired right up.

I think this bike of mine is starting to play with my head.

What is the chances somehow I am shooting raw fuel into the cylinder while kicking it. (I have my hand on the throttle whilst kicking, but I always rotate my hand forward as I kick)

This one has me baffled.


you're bike has probably always been on the verge of fouling. you just got unlucky.

can i suggest that you can lower the needle a clip and this will lean off the starting juice ratio a little. even turning the PS 1/2 turn for the winter won't do you any harm.


It's always possible. The only problem would be that if the throttle were open when you were kicking it, the kick starter would snap back up and try and take off your leg. I had to get in the habit of taking my hand completely off the throttle barrel because I broke a toe the first week I had my WR from the backlash.

By the way..what was the temp difference from yesterday and when you were fouling?

Bonzai :)

Taffy, Excellent idea. I'll give that a try and see if this dosent happen again. Thanks.

Yesterday it was about 60 deg in my garage and when it was fouling it was around 50 deg.

I think you may be on to something with the kickstarter kicking back because I remember it kicking back on me twice the day I was trying to fire it up. I guess from now on I will place my hand somewhere else just to make sure Im not gassing it.

Also, I'm going to try Taffys idea of dropping the needle. Like he said, couldnt hurt.

I probably need to mess with the carb anyways and clean out my accelarator pump.

I was wondering the same thing. I just did the BK mod, and before I put the carb back on, I went one clip position richer, (to #4 from #3) to make up for less fuel delivery. Well, I ended up fouling my plug right away, and the bike wouldnt kick over at all. Put in a new plug, and she fired right up. Took a spin into the woods, and as soon as I hit the mid range it sputtered, and slobbered down the trail. Im wondering if its the colder weather screwing w/ me? It was about low 40's today. Hmmmmm???........


I dropped the needle from #3 position to #2 on the clip.

I hope this helps. Ill let you know after my next ride.



Well what do you fmf power stroker sx-1.... temp just on freezing. Carb specs in my signature...original start jet with de-octopuss.

Now I know I got a lot going on here at once but heres the beef anyway

Fouled my plug on startup....put in a new one (a few sweaty minutes and about 40 kicks later) and it fired up on kick #2. Plug that was in was a CR9EK (Twin spark) and what I had been given by the dealer as a replacement was a CR8E. This is the first time I have changed plugs. I guess this made a huge difference.

Started blasting right away after warming up...fine for about 1/2 an hour but with surging iat about 1/4 throttle. Like a bat out of hell till almost WOT then somewhat slow to rev out.

After about a half hour starting to splutter and misfire in mid range so much so that I really backed off my riding cause the bike was unreliably performing. I had been doing a lot of low rpm work at that point. When I opened here up again on the stretch home it was a little better but that mid range splutter was still there.

Also she started to back fire a tad where before it hadn't at all, which I found strange as with a freer flowing exhaust I would have thought I would be a tad lean and would need to richen somewhat. Hmmm...

Pulled the plug again and it was black around the circumference but the electrodes were mostly clean.

So I guess I have to figure out which plug I really need (I know its in the archives somehwere). So this is what I figure....Taffy? JD?

Plug CR?E

Starter jet 65

Fuel screw in a half turn ?

Needle down a clip

Taffy, blasted the plugs with my bunsen burner. O guess I dont need to brush them ??

Cold air is more dense than warm air. It should be lean when the air is cold, not rich. I don't get it.

[ December 23, 2001: Message edited by: Stefe9999 ]


Wee bits-O Sand might be introduced direct to your cylender and other goodies. Just my .02 worth.


Originally posted by Stefe9999:

Here's a tip on the old fouled plugs. I use a sandblaster on the plug ends. They come out like new. Its a great way to get yourself some backup plugs.

Bad idea! Even if you blow out the spark plug with compressed air its not worth taking the chance there could be some trapped sand that could break loose later and do some damage to the cylinder wall. Spark plugs are fairly cheap. You might want to spend a little extra cash on the blue baby and give her some fresh plugs when it needs it.

Missle: I've always used CR8E. This is the plug that came stock with my bike. I'm not sure why yours wouldnt run crisp with it unless you have changed some settings on your carb.

Thanks for the input guys. I'll scrap the sandblaster idea. :)

what-o lads!!

been out of action for about 4 days due to my computer playing up.

now then, how many times have we got to say this WARM AIR IS CALLED A HIGH ON THE WEATHER CHARTS AND COLD WEATHER IS CALLED A LOW.

we're talking pressure aren't we. so infact the bike wants running leaner in the winter and don't forget that the goo in your filter isn't the same, that the fuel doesn't atomize so easily etc.

milkman i'm suprised you can't credit people with enough sense to clean the thread of a blasted plug.

i used to blast them, but and it's a big but-it's ok to do it on a cooking plug like the cr8e but when you start talking about gold palladium's etc then you're best getting a new plug.

all you need is a cooking plug to get it running, set up your jetting and then you can go to a harder plug.

the softer the plug the more the porcelain centre, electrode and earth stick out. this "exposes" them, they're "out in the open" it also means that they take the full heat of the combustion and they then can get too hot.

so the next plug has everything "inside" the plug to keep it away from the flame path etc and keep it cool. that's great when the bikes running high revs and perfect/lean jetting.

trouble is it ain't out there in the stream to help the bike to start and it can't burn the fuel off and get up to temp.

so as i've often said start with a cr7e and build it up. cr8e and when your bike is humming it should be good for a cr9e.

so come on lads, listen to someone who knows and next time someone gives out the wrong info (well intended i know)just straighten it all out for people and save them a load of money because any idiot can recommend you spend money. to me this site is about helping people by saving them money at the right times.

the missile

your needle needs to come down one or two clips so try that first. you may then find that the MJ could go up by 5 or 8 but you'll have to test.

by now you should understand the MJ feeds the needle and will affect it.

see how this goes first.

secondly do some snap and pop tests with the PS in and out this will be an indicator for your PC so report back.

good luck


Living in WI I run my 00 426 in 35 degree weather quite often, I actually have to squirt the throttle a 1/4 turn before starting and if I turn the choke off too soon it will lean misfire and die which fouls the plug, if I change plug it starts right up. Leave the choke on till it blubbers a little bit and then shut off choke. After learning how the change in temp. changes the starting procedure I've had the same plug in the bike for the entire year, about 100 hrs. My MJ ane PJ are one size larger and the fuel screw is at 2 turns, pro circuit T-4. hope this helps, mike

As far as sandblasting spark plugs, it is perfectly safe as long as you blow out the plug and clean the threads. Aircraft spark plugs have been cleaned by sandblasting since they were invented. Although it is not a bad idea to replace the plug when it needs it.

Originally posted by crs:

As far as sandblasting spark plugs, it is perfectly safe as long as you blow out the plug and clean the threads. Aircraft spark plugs have been cleaned by sandblasting since they were invented. Although it is not a bad idea to replace the plug when it needs it.

I dont mean to knock anyone else's idea.

After all, its your bike, not mine. :D:)

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