I recently acquired an HB .25 It seems to be finely engineered. Couple of questions.....what reputation does HB have? Any idea how it might compare to my OS .25 FX? The back of the engine is totally flush, with no part of the engine extending back, and it has mounting holes both for an engine mount, or you can mount it directly to a firewall. Would there be any advantage or disadvantage to mounting directly to a firewall? Seems like weight distribution might be a slight consideration...anything else? Wondering if you might have more or less vibration. What do you think?

[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.

[b]DSK:

See I missed part of your question. Radial mounting, directly to the firewall, would eliminate the weight of a separate mount. If you don't have to run your fuel lines through the center of the firewall, this mounting is practical.

A plastic composite mount does give some vibration isolation, but these little engines are smooth enough I don't think there would be any problem with the radial mount other than hose routing.

Just be sure to balance your props, and spinner if used.

Bill.

PS: Use a fuel with a castor/synthetic blend lube. They do not like all synthetic. wr.

Thanks for your reply Bill. Sounds like a pretty good engine. Not sure what I'll put it on. I put some stuff on ebay for a fella and he paid me with this engine for my trouble. Doesn't like synthetic huh? Thas a bummer as I use Cool Power 15. Might try it and see what it does. I'm assuming it won't hurt the engine.....uh, right?

[b]DSK:

Use synthetic if you wish, but a quick visit to your local drug store will get you a small bottle of USP castor oil, just dump two or four ounces in your gallon of Cool Power. The 15% is fine, I run the same for what that's worth.

No, the all synthetic will not hurt the engine, the ring will still seat to the cylinder by wearing to fit. There's the rub. Using castor oil the ring doesn't really wear to seat so much as it gets a varnish coating to match the cylinder wall. The cylinder wall will also get a slight varnish coating. Once these coatings are established wear is all but eliminated. Not so with synthetic oils, the parts just keep wearing.

Your choice.

Bill.