In order to get the idle down, the application of silicone rubber around the carb base is necessary (stop the air leak). The HP49VT has exactly the same problem and is an otherwise excellent engine. Yes, this comes from first hand experience. <G>

This particular series of engines utilizes a tapered shank on the bottom of the carb, so an o-ring doesn't work reliably. The silicone or butyl rubber seal works perfectly. You won't believe the difference this makes on these engines.

Also, be careful not to use glow plugs that stick down into the cylinder even the slightest bit. It will collide with the rotating valve and damage the engine. The plugs made by McCoy that look like normal non idle bar glow plugs work perfectly in this engine. These are the four-stroke McCoy plugs that I am referring to. Under no circumstances should you ever put an idle bar plug or an OS Type-F in these engines. Damage WILL result.

I liked my HP four-stroke. Sweet engine.

Ed Cregger