Thanks to Paul Czarnecki who disassembled his Fresh Breeze Ignition System to show us how to fix two of the more common problems. Like all two strokes, reliability is proportional to maintenance. Thanks also to John Black for instructions on replacing the wire that most commonly breaks (on those with certain ignition systems).
There are two problems we address: 1st is how to check the stator and replace if necessary, 2nd is how to replace the ignition wire that tends to break on some models.
One big caution: before working on these motors, it’s a great idea to remove the spark plug so they can’t accidentally start, especially with electric start machines. One experienced pilot mangled his hand when a motor started unexpectedly in the shop.
Tools in Use
1) Before removing anything, measure the stator coil’s resistance as described below. 2) The puller screws into a special threaded hole on the rotor. A center screw on the puller is tightened which pushes the rotor assembly off the crankshaft. Gear pullers can work but it’s hard to find them with small enough teeth to fit. Don’t pull on the aluminum starter receptacle which would likely destroy it.3) The various parts labeled before pulling off the rotor housing. 4) Closeup of the rotor and starter bell with the puller tool screwed in. 5) Using the special wrench (see below) and puller tool to remove the rotor. 5) Your target: the stator.
The Right Tools
As most know, it’s important to have the right tools. Using the wrong tools or using tools wrongly can inflict costly damage. Don’t ask me how I know that. I wish engine sellers offered toolkits that customers could buy that had the specific tools required to work on that motor. It would be a profit center for the seller and a stress reliever for the customer. Here are a couple tools that will help on the Simonini.
Paul Czarnecki modified this to make it fit readily on the Simonini.
The rotor wrench (above) holds the rotor while loosening the retaining bolt. As the name implies, the rotor, which holds the permanent magnet, rotates with the crankshaft. When taking it off, you need to hold the rotor in place while loosening its retaining nut. Holding the prop might also work but this tool makes it much easier.
Checking the Primary Stator Coil
If the motor gets progressively harder to start, it may be a shorting stator coil. Thankfully, it’s easy to check.
The stator coil is made of many, many thin windings with equally thin insulation. If that insulation breaks down, lazy electricity (and it’s all lazy) cuts across the short, decreasing coil effectiveness. The resulting low resistance is easy to measure. The far left mage shows which wires to measure with your Ohm meter. Pull the plugs apart and measure the wires leading upwards.
The stator output wires should be colored blue and black/red. The other wires are for charging if that is supported. Charging wires are dramatically shorter and will have a much lower resistance.
Normally, resistance is quite high since, although the coil is just a wire, it’s a very, very long, wire. About 300 Ohms is normal but if insulation is breaking down the resistance decreases. Below 190 Ohms the motor is hard to start and below 160 Ohms it’s nearly impossible.
If the resistance is less than 200 Ohms, the stator should be replaced.
Replacing the Stator
- Remove the starter housing.
- Remove the rotor housing. This may require a puller tool that screws into the hand start bell. See photo 2 under “Tools In Use”. The bell is aluminum and is easily damaged — use the right tool! Paul Czarnecki at PlanetPPG.com may have them available or know where to order them.
You may want to use heat if it’s being contankerous. Just blow hot air on the rotor unit it warms up nicely. That should expand it just enough to come off easier.
- From here the stator is held on by two bolts. Remove and replace then reverse the order of assembly.
Now go fly the thing!
1) Ignition system overview. 2) These wires come from the stator above to the secondary ignition below. 3) Not all engines use the same Stator. This is from a Nirvana version of the motor.