I have a friend that bought a 23HP Vanguard off of ebay then sent it to go devil to have one of their surface drives put on it. Anyway, he just put the engine on a 1648 Grizzly and the engine idles fine, dies out in the mid range, then runs fine at full throttle.

So I'm thinking the carb doesn't have a mid range circuit in it or that the engine came set up for an application where it would only run full throttle. Do any of you guys have any experience with this, I haven't messed around with his engine to check the carb but I'm wondering what you guys think could cause this. The motor idles fine, then with you give it some gas, it just wants to die out but picks back up when you approach full throttle. I know a clogged carb can cause something similar to this but being that the engine was new, I'm not entirely sure.

I'm also wondering if the engines MM manufacturers buy off Vanguard are just regular engines off the assembly line or does some tuning have to take place for them to work fine in a MM?