Chenery Aero V Twin

Home Model Engine Machinist Forum

Help Support Home Model Engine Machinist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Jul 16, 2020
Reaction score
Hi, I built the v twin from Hemingway castings and drawings. It’s pretty much as drawn with the exception of Hall effect timing and a TIM6 power mosfet board. The mechanical points just seemed like a bridge too far. Also, I wanted throttle control (the original drawings are a simple needle valve) so I used drawings from Mr. B Rupnow who I believe converted a design from metric dimensions for use on engines of about this size. So again thanks for that. I did adjust the jet size to match the drawings.
The biggest issue I had was getting enough compression. There were many trials and tribulations involving pistons, rings and valve seating. I have to thank everyone who posted their own compression issues on the forum with all the helpful advice associated. I finally made progress once I discovered I had uncovered a void in the no1 head casting exhaust seat. It was tiny and very difficult to spot, and fortunately I was able to lap it out, but my sanity was very much in the balance (more than usual) by then. My advice to anyone using the castings is to check for this very carefully.
The oil system was a mystery to me and I am still not sure if I have it correct so any comments are welcome. The plans speak of an oil reservoir feeding into the front bearing and show a passage up through the crank to the big ends. There is a PCV valve in the rear cam housing that keeps negative pressure in the crankcase such that oil is drawn in. I can report that it surely does draw it in and that a needle valve on the tank is very necessary or it will fill itself full in about a minute. I did start out with oil in the crankcase, seemingly with too much, and for the first few runs there was blue smoke and spattered oil everywhere. Now I think I have it balanced by opening the oil tank needle valve just a smidge to replace whatever is lost during operation. Anyway it doesn’t seem to be burning oil anymore and it hasn’t seized yet so maybe I am on the right track.
There wasn’t too much written about ignition timing in the documentation as glow plug operation is seemingly popular even with Mr. Chenery. After much experimentation I have it at about 20 degrees before TDC.
Its running on ethanol free gasoline.
Anyway, it’s been great fun and a tremendous learning experience and thank you for providing so much useful information on this site.

Regards, RS.
That's beautiful work! Thanks for sharing
Thanks Vietti . Yes that’s a great idea. Something like a non return valve set on the bottom sump plate with a short bit of tube internally (to keep a reservoir of oil in the sump) that fed back externally to the top of the tank. I’ll give it a try.