Return to the Lawn Mowers Forum | Post a Follow-Up

 o
Weak spark

Posted by ray_k z9 texas usa (My Page) on
Wed, Feb 28, 07 at 23:54

What is the cause of a weak spark on my 5hp B&S tiller engine? I replaced the spark plug and the spark is still weak.


Follow-Up Postings:

 o
RE: Weak spark

Replace the armature (ign coil) If perchance yours is an older point type ignition, put on the new style coil anyways and just nip the wire going to the points. The electronic ignition is by far a better spark than in the olden days. Bear in mind that a spark would have to be very weak in order to cause a no start. A person could check the flywheel key for shearing to cover all bases- especially if the either the flywheel nut (newer models) or starter clutch (older models) had been removed previously. Simply remove the flywheel nut or clutch, slide the washer off and inspect to see if the key is square w/ the keyway. Good luck.


 o
RE: Weak spark

Remove the plug wire.
Remove the plug.
Remove the shroud that covers the Flywheel.
Remove the two screws that hold the Coil to the engine block.
Use a small screw driver to find the magnet on the flywheel.
Use 400 grit sand paper to clean the magnet.
Use 400 grit sand paper to clean the coil.
Wipe the parts clean with a cloth as to leave no dust behind.

Take a piece of paper such as note book or typing and fold it in such a manner to get three layers.

Rotate the crank shaft so that the magnet is facing the Coil mounting tabs.
Set the coil on the tabs and let the magnet draw it to the flywheel tightly. This is called "Setting the air gap".
Install the screws that hold the coil and tighten them enough to hold the coil securely. Do not forget to install the ground wire with one of the screws.

Place the plug wire on the plug and place it where the threads are touching metal.

Spin the fly wheel by hand. You should now have a hot white to blue spark at the plug gap.

If it is a yellowish color. Look for other problems with the electrical system.


 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!


Return to the Lawn Mowers Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.


Learn more about in-text links on this page here