Question about Ryobi Factory Reconditioned 18" 40cc 2-Cycle Gas Powered Chain Saw #ZRRY10532
What is the magneto gap for a Ryobi 40cc PCN 4040 chainsaw please?
The gap needs to be as narrow as possible without any actual rubbing of the rotor against the magneto. The spacing is not as critical as with spark plugs or points (remember them?) since unlike those gaps there is no spark jumping across this gap.
Generally, as long as the magnetic field is strong enough, the magneto will produce the necessary spark at the spark plug. The closer the magnets are to the coil, the stronger the magnetic field will be across the coil, and therefore the stronger and hotter the spark.
I have replaced magnetos and they are simple to install, and almost impossible to mess up if you do it this way. All you need is a piece of thin cardboard (not corrugated). I use a glossy business card without raised lettering (so it slides easily), or the like.
1) Rotate the flywheel so that the magnets are NOT positioned in front of the magneto, then loosen both screws of the magneto so it can move freely.
2) Insert the business card between the magneto and the flywheel such that the glossy side of the business card faces the rotor.
3) Then BEND the business card back over each side of the magneto (in other words away from the flywheel) so it stays fixed and can not move from side to side when you rotate the rotor.
4) Then while pinching the magneto and ends of the business card tight between your fingers, rotate the flywheel to position the magnets directly in line with the two sides of the magneto.
Note: The magnets will grab the magneto and try to move it. As long as the slippery side of the business card is facing the rotor and you haven't removed the screws, it should move fairly easily.
Since the magnets want to pull tight to the magneto, but the business card thickness is the same across the entire surface, this gives you an even spacing between both sides of the magneto and the rotor. Essentially, the magnets on the rotor do all the work for you. with regard to alignment. As long as the magnets (flat shiny polished square surfaces on the outer rim of the rotor) align directly with the two faces of the magneto, the alignment is automatic.
5) Once you have the magneto and rotor in perfect alignment, cinch down both screws in an alternating method, first just to where they start to grab, and then back and forth a few times until they are firmly tightened.
6) Now, unfold the flaps of the business card and let it move with the rotor instead. You should be able to rotate the rotor away from the magneto and the business card should slip out easily. It may stay where it was or it may slide out from the magneto - either way will work.
7) Once past the magnets, the business card should come out. You may have to move the rotor back and forth gently a few times to get it to come free. When you are done, the magneto should be in perfect alignment with the face of the rotor and the rotor should spin freely without any rubbing.
8) Confirm the above and then reassemble and go cut some trees.
Posted on Jun 01, 2010
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Posted on Jan 02, 2017
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