Ignition coil

VegetiveSteam

Well-Known Member
Joined
Jun 1, 2022
Threads
0
Messages
446
Well I'm not sure where to go now with the backfiring. Coils been replaced carb cleaned new spark plugs ran sea foam through system
Look at post #10 of this discussion in the link below. Watch the video. It will show how to find valve overlap. If overlap occurs any place other than the piston being at top dead center at the end of the exhaust stroke your cam and crank are out of time with each other and that could cause backfiring. Just remember the four cycles or strokes. Intake, Compression, Power, Exhaust. What comes after exhaust? Intake. So with the piston at top dead center between the exhaust stroke and the intake stroke both valves should be open just a little bit. At top dead center on the compression stroke, both valves as you probably know should be closed

You can check it on either cylinder on your engine. You will need to take the spark plugs out and turn the engine over by hand in the normal direction of rotation which is clockwise looking from the flywheel side of the engine. Use something like a wood dowel to slide into the spark plug hole to feel where the piston is. Make sure the dowel is ong enough not to slide into the hole. You can use a screw driver if you're gentle and don't bang it around on the top of the piston. You're just trying to feel where the piston is.

 

stevieb50

Member
Joined
Apr 28, 2014
Threads
1
Messages
41
Look at post #10 of this discussion in the link below. Watch the video. It will show how to find valve overlap. If overlap occurs any place other than the piston being at top dead center at the end of the exhaust stroke your cam and crank are out of time with each other and that could cause backfiring. Just remember the four cycles or strokes. Intake, Compression, Power, Exhaust. What comes after exhaust? Intake. So with the piston at top dead center between the exhaust stroke and the intake stroke both valves should be open just a little bit. At top dead center on the compression stroke, both valves as you probably know should be closed

You can check it on either cylinder on your engine. You will need to take the spark plugs out and turn the engine over by hand in the normal direction of rotation which is clockwise looking from the flywheel side of the engine. Use something like a wood dowel to slide into the spark plug hole to feel where the piston is. Make sure the dowel is ong enough not to slide into the hole. You can use a screw driver if you're gentle and don't bang it around on the top of the piston. You're just trying to feel where the piston is.

 

stevieb50

Member
Joined
Apr 28, 2014
Threads
1
Messages
41
This is all I see in post 10. And would a compression check tell me anything and if so what should the compression be?
 

Attachments

  • Screenshot_20230911-052314-204.png
    Screenshot_20230911-052314-204.png
    182.4 KB · Views: 1
  • Screenshot_20230911-052314-204.png
    Screenshot_20230911-052314-204.png
    182.4 KB · Views: 1

VegetiveSteam

Well-Known Member
Joined
Jun 1, 2022
Threads
0
Messages
446
Click on the link at the bottom of my last reply titled "Kohler XT675-2047" Once there, go to reply #10. Go to the link in that video. It describes how to find valve overlap.

A compression test likely won't tell you anything because if the crank has turned inside the crank gear it's usually not far enough to notice on a compression test. Compression on a good Command Twin is typically somewhere around 180 psi if tested correctly. We like to see a minimum of 150 psi.
 
Top