Carb leaking into Cylinder when bike sits ?????

With a good plug, my bike will start right up and run well all day long. Lately, however, if I let the bike sit for a few days without starting it the plug will be fouled when I try to start it, it wont even sputter just nothing till I put in a new plug.

A friend of mine said that he heard that the 01' model has some sort of seal in the carburator that leaks when the weather gets cold, I assume leaking gas into the cylinder and fouling the plug.

Can anyone shed some light on this? I'm getting tired of buying $5 plugs. I guess what I'll have to do is to drain the float bowl before the bike sits for a few days and see if that helps.

Thanks for your help!


Search the board for plug fouling threads, there are quite a few. There also seem to be quite a number of different solutions. I do not remember very many lately about a bad carb seal.

Also you can often save the plug if you use the tube on a can of carb cleaner to clean it out really well (wear safety glasses!). That will often get enough of the goo off to have the plug back in working order.

Hey John i have the exact problem on my 01. I have to drain everything after i ride. Not bad only takes a few minutes.


Thanks Felix, that makes me feel a little better. After you started draining the float bowl after your ride, the problem went away?

And also, does it seem temp. dependent?

Thanks again,


My 01 426 seams to be vary temp. dependent. When its cool below 40 F and falling it runs rich due to the lack of oxygen in the air. I am going to start adjusting my air/fuel screw to lean it out and hopefully that will stop my plugs fouling.

John , mine is very heat dependent, it only started hapenning in the winter . In the summer I didn't foul a plug at all!!


Wouldn't it be a bit easier to simply turn off the petcock at the end of a ride and let the engine run for about a minute to get the float bowl level low?

I had the same problem, plug would foul after the bike would sit for a while or be transported. You have to do like Boit says. Cut off the fuel valve, but also ride it until it dies. I have been doing this since I saw it posted here. I have not fouled a plug since. The carb may leak, but after burning off the remaining gas it doesn't matter. That's what works for my '01. Later.

Thanks guys for all your help. I'm going to start either running the bike with the fuel off till it dies, or draining the float bowl.

It's funny that it didn't do this in the warmer weather.

P.S. Fastline, when the temperature gets colder there is more Oxygen in the air, so your bike should run lean in the cold...

Thanks again,


A good idea from the Aussie site is to always bring your piston up to TDC (valves-closed) position when you park it. i.e.: push kick starter till it stops hard. Personally, I always go a hair past using comp. release so it is ready to kick once & ride. No problems. If I intend to let it sit a day or two, I also let it run out of gas in the carb. Right or wrong, it seems to work.

time of the month.

Taffy :):D

The last thing you want to do is transport your bike with no fuel in the float-bowl. When the bowl is empty, the float bounces around, and that's not good. Check your float level, and check the seal between the needle and seat.

I have always drained my fuel at the recommendation of Clark Mason. I had the same problem as John and this cured it. Also my sons were "checking out" (read: twisting the throttle) Dads bike :)

When I come in from the last ride of the day. I turn my petcock off on the way to the trailer and then load the bike up while it's running. Then I just let it die.

I've been doing this since 99 and NO problems.


PS just got MY HD skid plate and will be ready to ride Tower soon. Reday to ride John????

[ March 21, 2002: Message edited by: Bill ]

I've been having the same problem with my 01' will not start at all if I leave the petcock on. I would'nt mind shutting it off and letting it run to drain the float but someone did mention excessive float vibration and that does make a little sense (although how much less it moves than when it has gas in it is debateable). Have you already tried the blue wire fix that I've read so much about. Haven't done anything to mine yet except for curse and replace over a dozen plugs last season and the dealer replaced the carb for free.

Originally posted by Fastline:

My 01 426 seams to be vary temp. dependent. When its cool below 40 F and falling it runs rich due to the lack of oxygen in the air. I am going to start adjusting my air/fuel screw to lean it out and hopefully that will stop my plugs fouling.

Not true. Colder air is more dense, meaning your bike will be lean as compared to a warmer temp. :)

Just out of can a 4-stroke have a carb leaking into the cylinder?? Doens't the fuel and air have to go UP, into the valving?!!

On a 2-stroke, it goes DOWN, through the reeds (which are not air/gas tight) and directly into the cylinder. With a 4-stroke, it would have to travel UP into the valves and through them then. This just doesn't follow normal logic....unless you guys are turning your bikes upside-down to transport them....

Actually, the intake runners are roughly ona flat plane with the outlet of the carb. The accelerator pump can shoot enough fuel down the intake runners to have it drip into the cylinder.

I like the post about bringing it to top dead or a little past to close the valves. I wonder if that might aid in a burst of fuel when kicked over and the valves open?

Tell me if you guys think this thought process has any merit. When I learned that the 01's were having a problem with the gas tank cracking, I heard that a possible way to prevent it was to remove the valve on the tank breather tube. As temperature increases, so does the pressure in side the tank and there is no place for the pressure to escape.

Since I removed the valve, I have yet to foul the plug. Before, I would have to change the plug every weekend before it would start.

Do you guys think there could be enough pressure to force the gas through the carb, through the valves and into the cylinder? Even if the fuel could not get past the valves, as soon as the starting procedure begins, the plug could be flooded with fuel. Just a thought.

And since I'm on the subject of spark plugs, I have had good service from Autolite 4303's. I can get them at Advance Auto for less than two dollars each, and they have a 2 year warranty on fouling.


Dennis-I don't think the fuel would be pressurized enough to force its way through the carb for a couple reasons (just thinking out loud here so bear with me).

One, if the petcock is off, I can't see the fuel getting past that.

Two, the float needle should seat well enough to prevent the fuel from making it past the bowl. Any fuel forced into the carb should run out of the overflow?

Sound reasonable?

I don't think some of these guys are turning off the petcock. I have never had any type of problem with bikes flooding or fouling plugs from a drive to the track. Then again, I always turn off my gas. That is one of the first things I learned growing up.

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