Got a puzzle with a Johnson HD26 I could sure use some help with.  When I run the unit, the high-speed needle seems to have no effect at all on the engine.  At whatever throttle setting, I adjust the low-speed needle to get it to smooth out. I can open or close the high-speed needle completely to no effect…it’s like the motor is running only through the rotary valve.

I’ve got two carbs for the unit and I’ve swapped those out as well as soaked, cleaned and replaced parts on everything that I could think of with no better results.  Engine seems fine otherwise.  Good spark, and compression runs a little over 75 lbs in each cylinder.

Any advice is appreciated! Thanks.

Tom Taylor