Froggy:

The cooling on the K&B ringed 61 is not an issue, most two stroke engines we use are over cooled anyway. That's why the 1/2A engines generally don't do well on low nitro, they just don't get hot enough. The K&B 61 is almost totally bullet proof, The Diablo pictured in my earlier post will take off vertically out of my hand. The 61 gives you the great power of the larger engine with the weight on the dinky 46 engines.

Sportsman Aviation is a brand name of Hobby People, [link=http://www.hobbypeople.net/guru/kws_57447057.asp]Here's[/link] a link to the Sportsman Aviation catalog page there.

There are four versions of the K&B 61 you will find most easily. Current production version is the 6550, it has the K&B "Ribbed" carb with the prop drive located by a centering cone. This same engine with the 0.375" bore Perry carb and built in pump is the 6560.

the earlier version had a cast aluminum prop drive located by a flat cut into the crank, this was the 6330 with the K&B "Block" carb, or the 6335 with the large Perry carb and built in pump.

The 6330 and 6550 are equivalent in power, all the parts will interchange except the crank shaft and drive washer.

The 6335 and 6560 are also equivalent, with all the same parts interchangeable. The pumper engines have about a 20% power advantage over the normal engines, if they are propped to take advantage of it.

The ultimate K&B 61 is the Clarence Lee modified engines with his "PDP" port modifications. This makes them even more powerful, but with the penalty of being noisier.

Even the least powerful of these four (or eight, counting Lee's PDP versions) will haul a 40-46 size plane with no problem at all.

There are newer design 60-65 engines that are more powerful than the old K&B, but you also get more weight, and shorter engine life. The only K&B 61 I've ever seen that was not economical to repair was crashed, it had broken the case.

Bill.