Dave, I've got a couple of the H-80's and they work real well. They use the OS 704 strap on muffler. The carburetor is an airbleed type and pretty simple to operate. Use fuel with castor oil and they will last forever. Try a hot glow plug, they idle down real well.

They make great engines for big trainer type models like the Senior Telemaster.
Mine are easy to start/run. One of the neat things about the rear carb version is you can remove the four screws that hold the front case/crank assemby and oil the bearings and plug it back in without having to remove the engine from your model.