Thanks AVB. I note this one is a relatively late engine for a Scott Bonnar 45 mower - earlier they used the 60102, 60202, and the equivalent 8 cubic inch engines, and from memory all of those had the adjustable main jet. However this one is a 91912, and may well have the fixed jet. We need the engine's type number, so we can have a look at the Illustrated Parts List.
