oh boy, yeah, sachs are a fun lot. i've still got my 2BX and i'm trying to decide whether to put it together and sell it before it explodes, or go through it and fix everything thats prone to breakage.
i've throughly trashed (as in, i dont think there is anything on it i haven't broken yet) my 1C, and i've written quite a bit about my trials and tribulations on various posts, but i can lay it down real quick for you, what you're in store for.
1st: your chain is going to rub, the motor mounts are too soft and when you put the extra power to the engine, the whole motor will twist and the chain will hit the case
2- The vibration of the rubbing chain will rattle out every single nut, bolt, and screw
3- the clutch will come loose because there is no positive engagement on the shaft, when you slow down (engine braking) it spins the nut loose. The heavier the bike, the worse this is, a G3 will do it almost instantly.
4- once you fix the clutch spinning loose problem, the tabs on the friction pads will get chewed up and break.
5- at some point you're going to break the coaster brake from doing skiddies drunk.
I'm working on making some replacement high durometer urethane motor mounts to prevent problems 1 and 2. I've also come up with a solution to problems 3 and 4, but haven't had a chance to prototype it yet. I'll probably do the 1/C first and if it works adapt it to the 2B... its going to be fairly expensive however, so i'm not sure if i'm going to go through with it, because all of you are cheap bastards...
Gearing up, by putting a tiny sprocket on the back, makes a huge difference on the vibration, but then you loose all your bottom end, and makes your clutch explode faster.
The manual motor isn't the solution to all the problems of the world that people trump it up to be. Mine came from a friend of Roald's in the netherlands, who got sick of replacing clutches.
The reedvalve athena is a sick bastard of a kit, it wrecks everything attached to it. If people were porting them correctly and putting them on E-5o's they'd be blowing them up, too. Buying a motor with more gears isn't going to solve the problem. Graham French took the two speed off his black G3 after about a season, I would assume because he got sick of fixing it, not much feedback comes out of that scene, so who knows, but it would be interesting to know what happened.