While at full throttle my Saito Radial suddenly sounded like it tossed a rod. I got it back on the ground only to
find that one plug wire had fallen off. Then I figured out why.
Text, photos and video by Tom Hintz
Posted – 2-12-2019
During one of the early flights of my Phoenix Model Waco, the Saito 60cc Radial powering it suddenly went sour. I had a sinking feeling that perhaps I had blown the engine and though way down on power I made it back to the runway where it quit altogether. Back in the shop I would find one of the plug wires hanging loose inside the cowl. I put the wire back on and the Saito 60cc Radial again ran like a clock.
While this was the first time, I had a Saito plug wire fall off, a friend who also has the Saito 60cc Radial had emailed me a few days before my incident asking if I had such a problem. After doing a little searching on line I saw that I was not alone in having errant plug wires on Saito engines. I emailed support at Horizon, who sells the Saito line and got an answer with a few photos showing how this wire system is supposed to work. Mine looked like that but didn’t work. The key turned out to be the groove in the spark plug, shown in the Horizon photos, and how that interacted with the plug wire cap retainer spring.
Fast forward a few days and I was in the shop looking at the plug wire caps and the spring clips meant to retain them. I could not figure out why that clip was not locking into the groove on the spark plug as shown in the Horizon response.
Then, I took a wire off the spark plug and looked inside. One side of the wire clip was in its slot in the cap and appeared to be in the right location to lock onto the spark plug groove. However, the other side of that clip was slanted outward and could not engage the groove on the plug.
I removed the clip from the wire cap and pulled the integral handles outward enough to bend it slightly, making the sides of the clip parallel to each other when relaxed, as they would be when installed in the plug wire cap. Now, both sides of the clip were now positioned where they can slip into the groove on the plug. I put the wire cap on the plug, and it clicked into place with virtually no force needed. I could tug on the wire cap and it would not come off the spark plug.
I suspect the clips become distorted by being put on and taken off several times. The distortion could also come from pulling the wires off the plug or forcing them on without using the integral handles. This is only a guess because now that I know the fix, I’m not overly driven to find the cause.
Initially I poo-pooed the response from Horizon but the photos and info they supplied acquainted me with the groove in the spark plug and how it interacted with the spring clip. So, thanks to Horizon, my Saito 60cc Radial runs great with all three plug wires on and I can zoom my Phoenix Model Waco around the sky with confidence. Now, if Horizon can come up with a source for replacement spring clips that does not involve buying a whole new ignition….
Have a comment on this How-To? –Email Me!