Question...why does this bike require waiting a few seconds after pulling in the clutch before shifting? What causes the gear to grind when I dont wait?
I like James' explanation of what's going on in the trans.
I would just add that one might also bear in mind that the Earles fork BMWs were designed as a dualsport bike.
They were designed to be both a solo bike and a sidecar tug, and while time has proven the bike a success in fulfilling its design mandates, it was not all that was hoped for as a successful business model.
These bikes were introduced in 1955, which coincidentally was the peak year for sidecar sales in postwar Europe; the economy had improved enough by then, so that people were starting to buy cheap cars instead of having to use sidecars for basic transportation.
I think Steib postwar production was up to something like 10-15,000 sidecars a year by 1955, but in six short years dropped like a stone to zero by 1961.
So BMW's vision of bike production for both solo and sidecar use was a few years late, and/or the postwar economic recovery was much earlier than expected. (go Marshall Plan!)
That was good for the everyday people, but bad for the likes BMW and Steib.
Earles bike production similarly dropped off to under 20 bikes a day by their last year.
Anyway, the point is that the drivetrain was designed around dual purpose, and specifically I'm thinking of the heavy flywheel.
The heavy flywheel is ideal for the rig having to drag around 2-4 times the weight moved by the solo machine, as well as easier starting with a magneto ignition; mags produce less spark at slower rpms, and so a heavy flywheel, with more roll-on to push against the compression than a lighter flywheel, gives more opportunity to spark the plugs.
And the heavy flywheel also allows that nice low idle that always brings a smile.
But a heavy flywheel is not so good for quick acceleration or quick shifts; heavy flywheel roll-on is slower to rev up, and slower to rev down.
Those who wished for a more go-fast approach used to opt for an aftermarket aluminum flywheel, (which I believe was just one third the weight of stock) though sometimes with mixed results.
To me, the sedate shifting has simply always been an integral part of the character of the Earles bikes, so when I want quick shifts, I get on a different bike.
Best-
George