I’ve never used a degree wheel before. I never understood the concept until very recently. I’m sure I’ll be A LOT better after I get and use one. I have a good understanding of motors in general 2 and 4 stroke. I’ve done mechanic work since I was a teen and I was a mechanic in the military for 9 years. I don’t want anyone thinking that I’m saying any of this to say that I automatically know these happy time motors. That part is me saying I am a visual thinker and I understand the internal workings of motors. I will say though that this has been my hobby/passion for 20 years now. I can’t leave well enough alone so I’ve tinkered and porter these motors before I even knew there were forums. I’ve messed up enough to have a good idea of what not to do. I have done exhaust ramps a few times in the past and every time I noticed a noticeably harder pull from starting from lower-mid range up to near 5500rpms. This time I know the ramp is too big. I’ll admit I had tunnel vision going when I did it this time. I took the jug apart yesterday and realized my exhaust port was A LOT bigger than the intake. I have no idea how I missed that but that would explain the really high torque but fall flat on its face in the upper mid-range rpm’s. I’m not sure if that answers your question but I’m here to learn.
I'm a mechanic too, and thanks for your service!
Like I mentioned, I've ruined a lot of stuff pushing the envelope, which is totally fine as long as we learn from our mistakes.
There are certain people who know the black arts of carbs, 2 strokes and more with no formal training and likely not the correct tools, but they are a dying breed, and I'm sure they have their fair share of mistakes.
I'm not going to pretend I know exactly what happened (aside from compression loss) but I would gather the engine is breathing easy hence the torque, but it's not scavenging the way it should, hence the face-plant at high revs.
Some of that MIGHT be fixed with a jet/needle adjustment or maybe just replacing the piston, or the jug us fubar.
I know a trick to lighten a piston is to keep the skirt length the same but make it skinny.
Again, I don't want to come off as a duche know-it-all, I was just responding as if this was your first forray into engines, so I apologize if I upset you.
There are quite a few that want to start the world on fire, but don't know which way to hold a screwdriver!