4g, g8 and some others are the best gearboxes. Then there's one that has the clutch on the jackshaft, to me that might be some power loss not having the clutch mounted on the shaft. I don't really think the bushing is a matter of beginners MB builders it's just a flawed design. It's like bringing problems of a 2 stroke to a 4 stroke engine. If someone puts together a perfected 4 stroke kit it would save people alot of annoying problems. The side adjustment bolts should all be m8 or 5/16. I snapped one of the m6 and then tapped all of them for 5/16. A DID or regina chain, arch tensioner, ngk plug and several other pieces will all help. For someone who can't do what you said they have to take the whole transmission apart or it will seize up on the clutch. AKA late to work aka bad design. The belt guides should be part of the whole jackshaft casting. The inner one wore through and left aluminum dust all over the motor mount and I had to rivet it back on. The oil will also soak into the belt and I'm pretty sure all belts are supposed to run dry.