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What causes spark plug fouling? (Read 134 times)
HappyHighwayman
Ex Member




What causes spark plug fouling?
12/04/09 at 16:03:09
 
History: My bike died on the way to work, so I had it towed to the garage. I had them do a tuneup, and everything seemed ok. A few weeks later I was again riding to work when it died. I pushed it up the hill to my house, and charged the battery and it would start, but the engine was pushing the fuel improperly and the ride was jerky and seemed to randomly accelerate.

Had it towed AGAIN, and they "fixed" it or so it seemed. I gave it a good ride, and it seemed ok. 2 days later, same problem. The bike's idle got weaker and weaker and eventually died and wouldn't start.

They took it apart again and say the spark plug was "fouled". They examined the jets to make sure they weren't making the engine run too rich, but they said it seemed fine.

They're not charging me for the 2nd repair, but what can I do to prevent this from happening again? I've used 3 of my 5 free tows from the American Motorcycle Association and would like to save the last 2 for an actual road side emergency Smiley


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Gort
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Re: What causes spark plug fouling?
Reply #1 - 12/04/09 at 18:38:09
 
1. Weak Spark

2. Erratic Spark

3. Fuel Mixture too Rich, Due Too:
a. Incorrect mixture adjustment.
b. Dirty Air Filter.
c. Choke is on, even if the knob is pushed all the way in.
d. Slightly ruptured or pin-hole in Savage petcock diaphragm, allowing vacuum hose to suck fuel.

4.  Too cold of a range Spark Plug, or Spark Plug set wrong, or Spark Plug is defective (check for fractures in the insulator and in the nose porcelain.)

5.  Oil fouling, Due to:
a. Worn or cracked piston rings, or cracked piston.
b. Worn Valve Stems, or valve stem guides or seals, depending on what an engine has.
c. Scored or ovaled cylinder.

6. Timing too retarded, which can happen despite your setting it correctly by eye, if the ignition system is controlled by a defective ECU management system.

7. Wrong Carb Jet size, without having made additional engine modifications to accommodate the increase in fuel being delivered to the engine.

8. Very old gasoline, or contaminated gasoline.

9.  Internals of the muffler have collapsed due to rust or fatigue, producing a partial blockage.

10.  A engine without an electronic fuel management system, whose  carburetor is not jetted for high altitude, but is always operated at high altitude.  
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« Last Edit: 12/04/09 at 23:21:30 by Arthur »  
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HappyHighwayman
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Re: What causes spark plug fouling?
Reply #2 - 12/04/09 at 22:43:29
 
Thanks a lot.

Is it possible I fouled it via letting it warm up too long with the choke on?

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EJID
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Work to ride and
ride to work.

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Re: What causes spark plug fouling?
Reply #3 - 12/04/09 at 22:45:35
 
HappyHighwayman wrote on 12/04/09 at 22:43:29:
Thanks a lot.

Is it possible I fouled it via letting it warm up too long with the choke on?



That's a definite possibility, used to happen to our older snowmobiles all the time.  Huh
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05 S40 15" Memphis Slim, FXDWG Bars, Moved Rear Signals, Saddlebags, Fork Bag, Mini-Tach, Raptor, Cone Filter, Fishtail Muffler, Mix Screw Out 2.5 Turns, 4" Fwd Controls, 147.5 Main/55 Pilot @ 4500
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thumperclone
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Re: What causes spark plug fouling?
Reply #4 - 12/05/09 at 00:51:57
 
EJID wrote on 12/04/09 at 22:45:35:
HappyHighwayman wrote on 12/04/09 at 22:43:29:
Thanks a lot.

Is it possible I fouled it via letting it warm up too long with the choke on?



That's a definite possibility, used to happen to our older snowmobiles all the time.  Huh

the ls is a four storke comparing to a sled is not relevant..
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thumperclone
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Re: What causes spark plug fouling?
Reply #5 - 12/05/09 at 00:58:01
 
make sure yor battery is fully charged (12 volts min)if wet cell type check the specific gravity of each cell
start bike and rev to 5k rpm
if under14 volts or over 15.5 volts dc  do the "ac generator" no load test
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Serowbot
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OK.... so what's the
speed of dark?

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Re: What causes spark plug fouling?
Reply #6 - 12/05/09 at 12:43:28
 
d.,... from Gorts list, would be my bet...  I hate that boogery stock petcock...

d. Slightly ruptured or pin-hole in Savage petcock diaphragm, allowing vacuum hose to suck fuel.
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Ludicrous Speed !... ... Huh...
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