Hi Guys,

Well I ran the CDI on the Saito at the weekend (picture of the sensor mounting attached). Here's the results, running on Southern ModelCraft straight synthetic and doing a direct comparison with an OS type F glow plug on an APC 16x6:

: tickover was stable down to about 1900rpm on CDI. Below that it would hunt around and the slow running needle was hyper-sensitive*. On glow it would also tickover at 1900rpm, but wasn't as confidence inspiring or steady.
: With the slow running needle set right for tickover/transition, the mid range was very rich especially around 5000rpm. Typical glow engine carburation, but interestingly it was more noticeable on the CDI than the glow ignition.
: Top end performance was identical, about 8300rpm on a safe-to-fly tune.
: No quantitative results, but it was definitely using less fuel on CDI even though the difference in slow running needle and main needle was only 1/4 and 1/8 turn respectively.

To be fair this engine only has about 40 mins running time on it, so I expect things to change a bit over next hour or so of running.

All in all, the CDI just works as it should. The rich mid-range is just a result of the specific carburation on the 125Fa I think. I might look at filling the carb barrel slot and milling a new slot profile to lean the mid range a bit. But before that my father's going to run it in a YT Cessna to see how it behaves in the air.

A

* I have my doubts about the carb on this engine not having a carb barrel spring in it. There is definitely some end-float in the carb barrel as a result and I wonder whether this was causing the hunting around by causing small changes in mixture.