PDA

View Full Version : Still fouling plugs!

studebakerman2001
4th March 2005, 00:48
My 70' ironhead is still fouling plugs. I found a broken compression ring in the rear cylinder and replaced it, but that did not fix the problem. The valve guides are perfect, the rings are all new. Both cylinders have around 150psi compression. It rides pretty good for a few miles then starts to sputter and miss, and once you shut it off it wont start again untill I change the plugs. Im thinking of pulling the cylinder again and checking if the ring broke again. One thing I did notice is the rear cylinder dose have a small scratch in it. It is a small horizontal line just deep enough to feel with my fingernail, could that be the problem? Let me know what you think. thanks guys.
dwardy
4th March 2005, 02:28
If you can feel it, oil can get through it. It sounds like a dress up/honing is in order. My guess is that ring broke at some point, causing the scratch.
willprevale
4th March 2005, 02:42
If you can feel it, oil can get through it. It sounds like a dress up/honing is in order. My guess is that ring broke at some point, causing the scratch.
Yup,my feeling too.
HrdlyDangrs
4th March 2005, 03:16
Assuming that you honed out the cylinders and installed the rings correctly and that you mic the cylinders and ring clearance is in spec....

You may have to go to the next size hotter plug. A #5 HD plug is 'colder' then a #4 which is 'colder' then a #3. If you have a number #5 plug, go to a number #4 and see if the fouling clears up or if the bike runs better. If it runs better but still fouls a little, go to the hotter #3 HD plug. These #Plugs are old harley referance #'s.

Also, check your timing and point gap. Make sure your wires are in good condition and double check all electrical connections from the battery, coil, points. You could be fouling the plugs from a weak spark.

If you are blowing oil past the rings and you can't get the scratch out with a cross hatch hone and still remain in spec for the given overbore of your current pistons, you'll need to have the cylinders bored out to the next larger piston size and rings.

try the plugs first. Let us know what happens.