Here’s an intriguing 2.5 cc (0.15 cuin.) sparkie which has come into the possession of reader Jim Conery. The initial impression is that it’s a home-constructed unit – it’s certainly no production model of which I’ve ever seen evidence. It could be an un-reported kit engine. The “T” cast on the bypass side doesn't match anything that I can identify from the spark ignition era, but it does say that the maker thought highly enough of his effort to identify it on the case. Jim says that the engine is in good condition except for one broken cylinder fin. It appears to have been mounted but never run.
Nominal bore and stroke are 9/16 in. (14.29 mm) and 5/8 in. (15.88 mm) respectively for a nominal displacement of 2.55 cc (0.155 cuin.). The engine weighs 6.9 ounces (196 gm). The oddly-oriented crankshaft induction system is timed for clockwise rotation viewed from the front – a not-uncommon operational mode in the 1940’s.
The cylinder retaining studs are 10BA and extend quite far beyond the nuts, a typical feature on home-constructed projects. The Lodge spark plug and BA fastenings strongly suggest a British or Commonwealth origin. The engine appears to have been designed to run inverted, as the needle valve is pointing down and the gussets on the engine's mounting lugs are located on the bottom side (or possibly the model’s bearers were intended to run above the lugs a la Forster .99).
The point wire terminal is a very classy battery nut. The measured point dwell period (points closed) is over 280 degrees, a highly inappropriate figure which would see off the batteries in short order and would also promote coil overheating and possible burn-out. Examination shows that this almost certainly arose from a mis-interpretation of the plan which resulted in a machining error, highlighting the probability that this is a home construction effort, likely from a casting kit. The design dwell period seems to have been a far more rational 90 degrees.
This engine is identical to that illustrated on page 212 of Mike Clanford's "A-Z" book - indeed, visible casting and other flaws suggest that it may the the very same example! Can anyone identify this engine or its origins? If so, please get in touch!
