The R26 considered as sidevalve

[BSA Bob]

Well, not quite but this is in response to the posts #1850-1852 on the "Wo war ich heute?" or "Where was I today" board.
Taz refers to the R25/3 as an "honorary side valve" because of its strong pulling power & since I've had my R26 running again I've thought about its pulling capabilities.

On some long hills my R26 will get down to about 60kph in top & then dig in & pull. The motor shows no signs of distress, no pinging or stuttering & when the grade decreases a bit the engine will gradually accelerate.
It's quite happy to potter at about 50kph in urban areas.

This is all fine by me but as the R26 engine is really meant to be revved would getting down to these low engine speeds under load be OK?

[BSA Bob]

[Heiko]

Hi Bob,

the R 26 engine thrives on revs. A hill? Downshift at the beginning of the climb and increase revs... then it'll go faster than 60 km/h if everything's in order. The R 26 is not comparable with the R 25/x.

If higher revs hurt you, you shouldn't buy an R 26. 

[4Taktix]

Hi Folks,
as my 'longstroke'-R26-engine is not yet ready ( intended to be put in an 25/3 carriage ), I can't really chip in
with personal experience here. But I often read similar statements on torque-comparisons, most of them
focus on R27 <-> R25/3(xx) though.
However - I'm scratching my head looking at the bare numbers, as both performance charts - R26 and R27 - 
show the power- and the torque-curve above the curves for R25/xx from idle to full throttle.
From the theoretical point of view this doesn't meet the common parlance.
Can it be more of a subjective sense, than tangible measurements ?
I can imagine the lighter Flywheel of the R26/27 as well as the quieter exhaust contribute to this.
But as I wrote - no personal experience up to now.

Now fire your guns ! 

Sascha

[Heiko]

As you've already realized, you lack experience... and even if you do have your "long-stroke engine" ready, it's still miles away from a stock R26 engine, right? If an R26 stalls on a climb at the same speed and in the same gear compared to an R25/x, it can't just be a feeling. Ride both and compare,...

[4Taktix]

OK Heiko - I'm looking forward to blow the Hoske-horn on your fast R27 next time
If you wouldn't prefer to join our conventions with any british steam-hammer or magneti-marelli fired Italo.
I know your R27 is also nothing box stock. Looks like such R27 or R26 without any 'tuning' is hard to find
amongst us. Allthough I had a trip to Iserlohn a month ago with another member and an untuned R26,
and I had to come up with all I got and all my /3 got, to barely keep up with his six.
But that trip in general was more racing-attitude with revving the gears out, hill up, hill down, no matter.
That day I couldn't verify the R26 having less punch compared to a /3 by no means.
To be honest - maybe this was due to our age-difference - he's a maverick and I'm almost an old fart 
Serious: He practices with his modern superbike on racetracks occasionally, so he knows how to drive fast,
even with an old bike. My experiences were more about riding offroad through dirt and mud.

[Heiko]

I do not have an R27   

Well... anyway... you mean your experiences are more about sticking offroad in dirt and mud. 

[4Taktix]

... depending on the tires and ground-clearence - yes. More or less.

But what happened to your 27 ? That thing with the Hoske-exhaust and the hot cam, red tank.

[Einzylindär]

The bike with the red tank is a R26.
The R27 was olive from military...and Heiko sold it!

I read all the old topics before I joined in 2018 to evaluate if a R27 fits to me or not...

As you may guess I decided a R27 fits and it does! 

best regards
Stefan, the one cylindrist

[Heiko]

... depending on the tires and ground-clearence - yes. More or less.

But what happened to your 27 ? That thing with the Hoske-exhaust and the hot cam, red tank.

Sach ma... too much beer at table 7?

[cwf]

You talk about riding an old BMW fast - this film is about a BMW twin but as an example of riding an old bike fast, it takes some beating :

[Heiko]

It's not about racing, but about being able to keep up with today's traffic and possibly having reserves.

[4Taktix]

There were some other Videos on YT with Troy Corser on pre-war BMWs - absolutely awesome ! 

@Heiko Table 7 is completely dry - maybe that's the problem 

[BSA Bob]

Thanks for the thoughts. So long as the lower revs don't hurt the motor I'm happy to ride it like this. Only where possible though, I don't want to lug it & most of the time it's revving happily.

[4Taktix]

From my opinion no problem, as long as you don't overplay it.
e.g. accellerating on an incline in 4th gear at 35 kph or similar.
Consider there's the spring-mechnism with the curved dogs on the main-shaft in the gearbox,
exactly to smoothen the pulsating power-input from a single cylinder to 'protect' the gears and drivetrain
from hammering load peaks.
The comparable heavy flywheel also contributes for smootheness.
All in all you can say this thing is built 'foolproof' - not much left to worry about. 

[strichzwojan]

Any sensible fellow will easily find the point when its necessary to shift the gear. You can go in low revs, but you NEED NOT!

[BSA Bob]

Once again, thanks for the thoughts. I guess my concern about low revs was the danger of stressing the big end.
I certainly don't let the poor thing get down to faltering or stuttering revs.