I've got an old something or other that i have been flying on a pretty heavy 30% Ace extra 230 that, even after seeing it, CH Ignition could not identify. I'm hoping that someone out there (Ralph @ RC Ignition?) will be able to I.D. the engine from a written description since I can't seem to download a picture.

The engine has a single slanted Bosch plug and CH Ignition. There is a polished aluminum conical shaped adapter on the front of the engine to provide a location for the ignition sensor and spacing. In front of that is a single bolt prop adapter with 4 bolts retaining it.

The crankcase originally used 5 bolts to hold it together. Viewed from the top of the cylinder down, with the prop shaft facing away from you, three of the crankcase bolts are on the left, with 2 on the right. The case was powder coated a medium metallic blue. There is no indication of a previous color. There is a 1/4" pressure fitting on the left side of the crankcase, just below the carb. The rear of the crancase has a square, flat aluminum plate with an approximately 1-1/4" circle cut out of the center to allow for a round, hard steel section of the engine to pass through.

The carb used is an old Walbro "SDC". On the diaphram side of the carb, just behind the needles, "J3" is stamped in a depressed double circle. In a depressed single circle to the right of the needles, "40" is stamped.

On the rear base of the cylinder, the numbers 5015333 are stamped, separated by an "S" overlaid with a "K", in a casting. After the "S,K", the numbers 1654-5 are cast in the base of the cylinder. Over the "S,K" are three small "plusses" (+++), which are also cast, not stamped. The top of the cylinder, on a raised cast tab, has a cast "6" with 6 small dots cast in front of it. Also lightly stamped on the raised tab is the letter "B". In a very small stamp, is the number "6", just over the top of a smaller stamped "T.51

That's about all the description I have to give. If anyone knows of this engine, I would appreciate knowing it's type, size, and approximate age for future rebuild purposes. Thanks in advance.

The Walbro book says the SDC 40 carb was made for a Lombard chainsaw, but the chainsaw book says the carbs used were either Tillotson or Walbro WA, not SDC...
The K and S are the symbol of Kolbenschmidt, the company that made the cylinder...The B on top of the cylinder is for sizing the piston mfor piston to cylinder clearance....There usually A, B, and sometimes C pistons..The sizes are only about .0003 apart, but a C or B piston should not be used in an A cylinder...I have a few old engines here, maybe I can find a match to the cylinder...

Thanks, Ralph. I appreciate your help. You're the person I am going to send the engine to for a re-work when the time comes. Also, this is the engine I mentioned in a side conversation with you a few weeks ago.

Pat