I have a 521 from an 87 Formula plus in my 91 Formula MX. I had to swap the motor Boy borrowed it and didn't put injector oil in it!
I have added the 40mm carbs stock setting from the 86-87 Formula plus
Regeared to the 26 /38 crankcase
It now has some real gitty up go!
Hey what should the top rev's on that motor be with the original gearing and 40mm carbs?
It really jumps on the power curve up around 58-6K rev's
I had it out on the side of the road and it hung in around the 7200 -7500 @130 KPh according to the speedo and tac but if you jumped on it it would run up to 8K real quick
More snow Please!!!!!!!!!!!!!!!!!!!!
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