bought a mystery 850 double pumper...

mbaird said

Like I said.. I just bought it as a curiosity.
At the very least I got a set of 50cc pumps and other various parts.
I have another 850 DP and it seemed to work fine for a street motor.
My favorite though is a 600 DP the was modded by a buddy in the 80s... Seemed to make any engine run just a little better

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That's what I'm saying...it's not an 850 it's an 830. Two entirely different things. I could be wrong but I don't think so. The only way to know now is to measure the base plate and the Venturi. I think you'll find it's a 850 main body with a 750 base plate. Even if you blend the two at the base plate, it causes fuel curve issues. The only way it's an 850 is if someone installed annular boosters in an 850. Otherwise it's an 830.