If true, what causes this condition. Head design ? Carburetors ? Both ? Am I not holding my tongue correctly during kickstarting and after it fires up .
What’s your opinion ?
Note: Like any engine it is not a good to start and drive without some warmup
54 R51/3 55 R50/Velorex 560 sidecar 64 R27 68 R69US
So with the vintage boxers (and singles for that matter) the heads and the full intake system needs to get warm. On a cold day, from a cold start getting the heads warm can take a good long while. A short ride at gentle throttle (once the oil is a bit warm) is probably the best way to warm up an engine like this.
If you engine starts we’ll, and gives full power nearly cold, I would guess that it is running too rich once it is fully warm. Plugs can tell that to an extent, as can a exhaust gas temp check...not something that most of us can do.
So Charlie, recognize anecdotal information for what it is: anecdotal; you had one good reference point there: your own experience.
And now several more were been added from members responding to your quest for their experiences.
I think it's also important to put your question in context.
When these bikes were current, many folks were drawn to them as an alternative to the Brit offerings of the day, which at the time had broad appeal similar to that enjoyed by Japanese bikes today.
The jacket on English bikes was they were great rides, with all the power and handling, but in need of constant upkeep.
While the rep with the BMW at the time was one of perhaps a more elegant if sedate ride, but needing little in the way of maintenance.
The truth on both was somewhere in-between.
The BMW did require comparatively less maintenance, but certainly not no maintenance.
I grew up next to a one-man BMW dealership/mechanic shop, and he had two distinct groups of clienteles, one group made up of the doctor/lawyer/professional types who brought their machines in methodically for regular service; the other (perhaps larger) group were those who limped in only when they had problems.
When I got my first BMW at 19 or 20, I fell into the second group; never had funds, just wanted to ride, and allowed myself to remain ignorant of the consequences for far too long.
So what I saw was many (like myself) who ignored the owner's manual recommendations.
My old owner's manual (same one as yours) says some interesting things, like: remove, dismantle, clean, refit, and readjust the carbs every 4k miles.
Not many did that back then, I know I didn't. (any guesses on how many follow those recommendations now, even with the E10?)
Many rode rode till something broke, and then addressed it.
"Or, maybe it’s Model specific."
Well, the S models were sport models because they had higher compression, greater valve overlap, larger diameter carb venturis.
Being a bit more high-strung also meant being a bit more susceptible to anything being out of whack.
For example, those larger throats meant that the air passing through the carb moved at a slower speed during idle than with the smaller carbs, so if the idle tuning was not spot on then good atomization was not either, and both the idling and the ability to move off idle to the main circuit would suffer.
So my answer to your question is- it depends.
There were (and are) the bikes that followed recommended protocol, and are quite capable of the manual's 3-4 second tickle to cold start and go consistently; there's the bikes blessed with the same good design but cursed with inadequate maintenance; and bikes in between with every manner of condition.
All were observed and experienced by a wide range of people drawing a wide range of conclusions.
That the /2 reputation has endured intact with such a strong following this many years on, tells me that overall there was more observation and conclusion drawn from the good examples; while the bad examples were largely recognized for what they were- bad examples.