Hey trickedout, thanks for picking up one of our engines. As the other guys mentioned there is a small o-ring that is slid over the neck of the carb and sits up against the block. Normally carbs do not have this but we put it on as an extra sealing mechanism to stop the possibility of any debris or gunk getting into the area where the carb/block is joined. Basically I decided to do this because it has the same effect as adding air seal that a lot of people like to do without the mess that putting that stuff on creates.

As I mentioned I do not think that anyone else does this so it probably looks a little unusual. In hindsight it probably would have been easier if I chose not to do this (as I would not have so many questions to answer lol) but it works and in my personal opinion offers a better seal and/or solution to adding air seal/silicoln like a lot of people seem to do. If you choose to leave this thin o-ring in, the carb will end up sitting approximately 0.5mm elevated from the block, this is not a problem and is perfectly acceptable. You have the choice of either running this or removing it in which case the carb will sit flush against the block. Again it's 100% up to you, the user on how you want to do this. Hope this helps explain things as well as gives you a better understanding of why it is like this.

Regards,

Ron