Hard Start of First Try
My 915iS with 90 hrs TSN suddenly became hard to start smoothly but only on the first time. It ignites right away, but runs very rough, and requires significant throttle increase to keep running. It smooths out after about ten seconds and runs clean and smooth thereafter. If I do a shut down after smooth running, then the next start is fast and smooth. Startup is very similar to a radial engine where one needs to keep hitting the fuel primer to keep it running until all cylinders are firing smooth. I found a couple spark plugs were darker than all others, and minor lead deposits. I always use 94 UL, with no ethanol. A brass wire brush spark plug cleaning had no effect.
If a couple hours have elapsed, then the first cold start will repeat the initial roughness. Rough running will only achieve about 700 RPM until it runs smoothly.
Suggestions where to look?
