Bendix Carb? Doggy in the midrange

[Cabindweller]

I am still having issues with my 74 600. It has the Bendix. I went through the intire sled this summer, I replaced the outer crank seals and I got the timing set dead nuts. The other day I topped it off with with 3 gallons if race gas and a gallon of 91 mixed. I know that race gas burns slower and that it will not necessarily make the motor perform better, but I wanted to give it a try. There was also a gallon of 91 in the tank. After all the work I have done it is still doggy in the midrange from say 25-35 mph. It seems to be less pronouced when the motor is cold. Once you break 35ish it gets up to 50-55 pretty good. Yesterday a friend and I put on 6 miles just exploring about in fields. My 600 ran fine as we never really went over 25. This afternoon I was out making high speed runs and tweeking the jets. It seems to clear up if I lean out the low speed jet. That don't make sense dose it? For one it wont Idle set that lean. Now also this is the second motor this carb has been on, the other motor had the same issues before I burned a cylinder mostly due to my own stupidity (bad seal replacement). I should also add that I went through the carb this fall and cleaned it up good, and made sure the float is at spec. I also put a new gasket kit in. Also I bought a brand new Mikuni fuel pump for it last year. I am starting to think it has to be the carb. Tomorrow I am going to top off the fuel tank with 2 gallons of 87 to try to bring the octane back down to around 90 something. If that has no effect I do have a spare Bendix that needs to be gone through that I am going to try. If that dosn't help I have a HD tilliotson I might try. I feel confidant that my new seals are not leaking although the center seals could be to blame. Although I was told that bad center seals will make a motor into a hard starter and mine starts on the first pull almost allways. Granted I have a primer, But I have used the choke just for the heck of it. One other thing is the compression is good at 145 per side. I am getting frustrated. Any Thoughts? Clutching?

Jerry