I've always liked single-banger motors. Would it be possible
to modify a BMW boxer motor such that the 2 cylinders'
power strokes were simultaneous instead of alternating?

In effect it would be equivalent to a thumper
but better balanced for less vibes.

SQ

On Apr 18, 11:59*pm, sean_q <no.s...@no.spam> wrote:
> I've always liked single-banger motors. Would it be possible
> to modify a BMW boxer motor such that the 2 cylinders'
> power strokes were simultaneous instead of alternating?

*Anything* is possible. All you have to do is pull the camshaft out,
saw it in half, rotate the halves to achieve the firing order you
want, and weld them back together.

http://www.bikebandit.com/1973-bmw-r...m295#sch324018

On Apr 18, 10:59*pm, sean_q <no.s...@no.spam> wrote:
> I've always liked single-banger motors. Would it be possible
> to modify a BMW boxer motor such that the 2 cylinders'
> power strokes were simultaneous instead of alternating?
>
> In effect it would be equivalent to a thumper
> but better balanced for less vibes.
>
> SQ

Xposting to reeky since it's pretty slow

Ought to be a piece of cake on a BMW oilhead,
as there's a separate cam for each head. That may
leave some interesting problems with the fuel injection,
but hey, how hard a hack could that be ?

http://tinyurl.com/3m3x3gr

Reeky eagerly awaits the results of your experiments.

Rob Kleinschmidt <(E-Mail Removed)> wrote:

> That may
> leave some interesting problems with the fuel injection,
> but hey, how hard a hack could that be ?

I'm sure Sean would tell us ;-)

--
BMW K1100LT Ducati 750SS Kawasaki GPz750 Honda CB400F
Triumph Street Triple Suzuki TS250ERx2 GN250.
Try Googling before asking a damn silly question.
chateau dot murray at idnet dot com

On Apr 22, 8:13*am, sean_q <no.s...@no.spam> wrote:
> On 4/21/2011 6:29 PM, Rob Kleinschmidt wrote:
>
> > Reeky eagerly awaits the results of your experiments.
>
> Yesterday I phoned Shadbolt Cams Ltd in Vancouver.
> They would need a cam billet because too much material for welding
> would have to be added and then ground to fit in order to relocate
> two of the lobes 180 degrees (that much heat would warp the camshaft).
>
> However they do have a regrinding master pattern for the 1970 R75:http://www.shadboltcams.com/cycles.html
>
> The cam lobes are in pairs, but within each pair the lobes are not
> quite parallel; they're a few degrees apart. I can't figure this out.
> At first thought, why would the cylinders seem to have different
> valve timing -- and how would this relate to ignition timing?
> Are the cylinders not quite horizontal and 180 apart, or is it
> (on 2nd thought, duh...) merely because the pushrods are at an angle.
>
> The ignition fires at (or near) each TDC so there's a wasted spark
> at the end of the exhaust stroke. This feature would give me ignition
> on both cylinders at compression TDC (theoretically).

As I said though, if you could get the injection working,
an oilhead engine might run using absolutely stock cams,
as each oilhead cylinder runs off its own chain driven cam.
I believe the oilhead is also lost spark ignition.

Might even be something that could be cobbled up in the
garage with no machining or electronic trickery. Not sure
what's involved with the F.I. system.

Rob Kleinschmidt wrote:

> Might even be something that could be cobbled up in the
> garage with no machining or electronic trickery. Not sure
> what's involved with the F.I. system.

It would be no problem at all to hook more than one injector up to fire
from the same signal as the other injector, you'd need to use a driver
circuit rather than just put the two injectors in parallel[1], but it
would be pretty trivial.

[1] which would probably work for a little while until the output
transistor in the EFI computer blew out.

On 4/21/2011 6:29 PM, Rob Kleinschmidt wrote:

> Reeky eagerly awaits the results of your experiments.

Yesterday I phoned Shadbolt Cams Ltd in Vancouver.
They would need a cam billet because too much material for welding
would have to be added and then ground to fit in order to relocate
two of the lobes 180 degrees (that much heat would warp the camshaft).

However they do have a regrinding master pattern for the 1970 R75:
http://www.shadboltcams.com/cycles.html

The cam lobes are in pairs, but within each pair the lobes are not
quite parallel; they're a few degrees apart. I can't figure this out.
At first thought, why would the cylinders seem to have different
valve timing -- and how would this relate to ignition timing?
Are the cylinders not quite horizontal and 180 apart, or is it
(on 2nd thought, duh...) merely because the pushrods are at an angle.

The ignition fires at (or near) each TDC so there's a wasted spark
at the end of the exhaust stroke. This feature would give me ignition
on both cylinders at compression TDC (theoretically).

SQ

On Apr 22, 7:43*am, Mark Olson <ols...@tiny.invalid> wrote:
> Rob Kleinschmidt wrote:
> > Might even be something that could be cobbled up in the
> > garage with no machining or electronic trickery. Not sure
> > what's involved with the F.I. system.
>
> It would be no problem at all to hook more than one injector up to fire
> from the same signal as the other injector, you'd need to use a driver
> circuit rather than just put the two injectors in parallel[1], but it
> would be pretty trivial.
>
> [1] which would probably work for a little while until the output
> transistor in the EFI computer blew out.

Simple slave setup should do it ?

No per-cylinder feedbacks to worry about I guess.

An 1100 oilhead ought to be about the same price
as an airhead these days.

Go for it Sean. We'll hold your coat for you while you
do battle with this project.

Rob Kleinschmidt wrote:
> On Apr 22, 7:43 am, Mark Olson <ols...@tiny.invalid> wrote:
>> Rob Kleinschmidt wrote:
>> > Might even be something that could be cobbled up in the
>> > garage with no machining or electronic trickery. Not sure
>> > what's involved with the F.I. system.
>>
>> It would be no problem at all to hook more than one injector up to fire
>> from the same signal as the other injector, you'd need to use a driver
>> circuit rather than just put the two injectors in parallel[1], but it
>> would be pretty trivial.
>>
>> [1] which would probably work for a little while until the output
>> transistor in the EFI computer blew out.
>
> Simple slave setup should do it ?
>
> No per-cylinder feedbacks to worry about I guess.
>
> An 1100 oilhead ought to be about the same price
> as an airhead these days.
>
> Go for it Sean. We'll hold your coat for you while you
> do battle with this project.

Even without doing anything to the injector timing at all it would
still probably run OK-ish- it's not as if the fuel spray has to be
timed exactly to the opening of the intake valve on a fuel injected
engine, check Wikipedia's entry for the various flavors of multi-port
fuel injection, esp. simultaneous mode.

On Apr 19, 12:59*am, sean_q <no.s...@no.spam> wrote:
> I've always liked single-banger motors. Would it be possible
> to modify a BMW boxer motor such that the 2 cylinders'
> power strokes were simultaneous instead of alternating?
>
> In effect it would be equivalent to a thumper
> but better balanced for less vibes.
>
> SQ

Basically you want a big bang motor from a twin...you can do that with
a harley it's called a twingle.