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I might try going pre-mix, what ratio is best for the MT?
With the stock jetting (which is set up for no oil in the gas at all, and is super lean)? The less oil you use the better the carb will probably work, but I'd suggest you jet the bike for pre-mix instead and use a good oil in the 36:1 - 40:1 range (I use Bel-Ray H1R at 36:1). The pre-mix '75 I worked on had much better throttle response & bottom end with a #65 pilot jet and would surely have liked a 70 even more, and I think the main jet should be at least a 122 or 125 for pre-mix, maybe larger (a 2.5 throttle valve might be worth trying too). An interesting richness/leanness test in these bikes is to set the needle clip to the #1 (leanest / top position) and test ride at 3/4 throttle, then move it to the #5 position and repeat.
Ray