[Brewgyver]

Not familiar with that specific motor, but many small OBs have a roller/cam linkgage to the actual carb throttle arm. This roller rides on a cam which advances with the magneto. In other words, when you manually increase throttle, it's advancing the mag pickup in relationship to the flywheel, and the cam is pushing the carb throttle to match. It could be a simple case of gummy linkage, so when it gets pushed open it tends to stick. Find the cam/roller and try pushing it to open, then let your finger slip off of it, and it should snap right back up against the cam on the magneto.I would start by looking at the throttle linkage and carb throat. Disconnect the fuel, and if it has a kill switch leave it in the no-run position. Use spray carburetor cleaner throttle lever where it attaces to the , while you're operating the throttle lever directly with your finger (usually just takes a downward push). Clean things up and check it out.

 

[Brewgyver]

Thanks for your reply, however, I'm unfamiliar with some of the terminology that you have used (apologies).

I can see two things that can alter the carburettor. The throttle cable and the choke arm. Are you saying to just check whether these are both springing back as they should and that they are not gummed up?

I'm having trouble finding a good diagram or picture of your model, to show you what I'm talking about. Could you remove the cover, take a picture and post it?