Re: too rich fuel mix?
Ditto to Map's post and I'll add two things. These ahev been covered many times before but it doesn't hurt to refresh even in an old thread.
When you decrease the oil content in your mix you effectively increase the fuel ratio. This will equate to a richer condition in regards to air/fuel which might show as four stroking, loss of power etc.
When a builder is running 16 or 20:1 and tunes his carb to that ratio he can expect a rich condition when he moves into the lower oil to fuel ratio, 32 or 40:1. I'm one of those guys Map mentioned who uses a 100:1 ratio. At those mixtures leaning the fuel to air mix is essential.
A 50:1 mix, if the oil is formulated for that ratio, will require you do some experimentation with jetting to get the most from your engine.
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