Hard starting...and the cure!

[ChrisBolkan 130]

So my 912 has been taking longer to start as it has been getting colder and running very rough and shaking hard while it gets going. I assumed it was just the thicker oil causing it to crank slower. I am thinking this rough starting contributed to my exhaust cracking.

Anyway the last time I changed the plugs was a while ago, before I flew the plane to Oshkosh on Avgas the whole way. So, I bought a set of plugs and put them in this weekend thinking changing them out might help.

When I removed the plugs they were actually a lot cleaner than I expected. I had removed one or two after oshkosh just to have a look. There was some crud around the electrode and insulators but not so bad that I thought they needed replacement. I decided to keep running them since it was starting and running great, but it was still summer. 

When I took them out this weekend they looked a lot cleaner than when I got back from Osh, but the gap had REALLY widened out! That was surprising because the nothing looked eroded, but the spark gaps were definitely in the 030+ range!

I put the new plugs in with a "tight" 025 gap and all I can say is WOW! New plugs not only made the plane start WAY faster, they smoothed up what has been a SLOW deterioration in engine smoothness. The deterioriation in starting and smoothness was so slow that it had gone unnoticed until it finally became a problem.

So if the colder weather seems to have affected the way your plane is starting and running, Change the plugs! You will be SO happy you did!

Chris

[Av8r3400 1179]

I actually run mine at .021-.022" gap for the same reason.