[b]Dak:

I've had several Helmut Bernhardt engines, my remaining three are 25s. One is a standard version, I'm keeping it for spares, the other two are the HB 25S engines. The 25S engines are going on my TwinStar.

They are loop scavenged, I wouldn't be surprised if the Schneurle ported 25 FX was more powerful, but the HB engines are comparable to the old Magnum 25 GP engine on my Eaglet.

The HB 25s have ball raced crank bearings, and a Dykes piston ring. Unlike the larger HB engines, all the 21 and 25 engines came with Perry carbs as standard.

The crank case is made to allow either beam mounting on an ordinary engine mount, or radial mounting (to the firewall) with three lugs at the back of the case. The disadvantage of radial mounting is the cylinder fins - they extend further to the rear than the plane of the radial mounting lugs. The engine has to be spaced away from the firewall, or the firewall has to be cut away to clear the fins, or not extend to the point where the fins would hit.

My 25S engines. One is NIB, the other has been zero timed, so I'm effectively starting with two brand new engines, even though they were built in 1982, one in April, the other in May. Production date is stamped under one of the mounting lugs.

Currently the engine design and all parts production is owned by Mecoa, I got the parts for the overhaul from them.

Pictures attached, the only difference I can find between the normal and S models is the external finish. Just imagine the pictured engine in plain metal, that's the normal version.

More questions? Ask.

Bill.