Grumpy, thanks for the welcome.
Yes I'm not thrilled at the engineering of a taper and the tiny spline all made from zinc. I'm used to machine tool tapers (on lathes and mills). They grip as soon as you fit them. Anyhow, I have checked carefully, the surfaces here are clean and undamaged. However there is a slight rock when the tapers are engaged, so there is no true taper fit. How it was originally made to fit in the factory is a mystery to me.
Perhaps I'll try just yanking down on the clutch plates as hard as I can. If it still spoils, I'll have to get another tip-shop trimmer of the same make, use its crankcase, but this time not take off the flywheel - leave the mysterious factory fit of the taper well alone.
The 30cc is also a half-crank machine. However, at the tip-shop it is the best of the commonly found trimmers. One could say that if there's piles of them at the tip shop, that might be giving some kind of message as to quality.
So why bother? Well, its a big leap from spending $15 at the tip shop to buying a secondhand Stihl. If my rebuild works, it will be kudos. And, at least I'm cutting my teeth on a $15 outlay, rather than making beginner's mistakes on a high-end machine. I've learnt a lot so far.
