New motor

Jon P · Oct 30, 2007

It seems that the new 1200S has twin over head cams............any one else seen this?

I can only assume that it will end up in all the bikes - and BMW always said that the resulting motor would be too wide.

Though I reckon if you compare the 'oilhead' boxers of the last few years to the older airheads it seems that the motors have progressively been getting higher and higher thus allowing a wider motor to be used.

Wapping · Oct 31, 2007

Jon P said:
It seems that the new 1200S has twin over head cams............any one else seen this?

Yes, it does have twin overhead cams.

Damir · Oct 31, 2007

terayon · Oct 31, 2007

you can't call them overhead cams as there not actually "overhead"

Gizmo · Oct 31, 2007

Explain your reasoning :confused:

Jon P · Oct 31, 2007

Yes, do please explain.............what I see is a modern dohc design with a shallow inclined valve angle (as opposed to the older himispherical design) and a compact drive system system with small cam sprockets.

Definately an ohc design - just can't explain why now after so many years of BMW saying that they can not make one due to engine width reducing cornering clearance.

terayon · Oct 31, 2007

definition. (DOHC) An engine with two camshafts located above the cylinders. One drives the intake valves and the other operates the exhaust valve.

notice the use of Above or Overhead, on a flat twin everything is mounted on the side. BMW only state twin cam, I've not seen them use the term "Overhead" yet. Even Ducati just use the term "twincam" as one of theirs is on the horizontal level.

Gizmo · Oct 31, 2007

terayon said:
definition. (DOHC) An engine with two camshafts located above the cylinders. One drives the intake valves and the other operates the exhaust valve.

notice the use of Above or Overhead, on a flat twin everything is mounted on the side. BMW only state twin cam, I've not seen them use the term "Overhead" yet. Even Ducati just use the term "twincam" as one of theirs is on the horizontal level.

What do Porsche call the location of the camshafts...... :blast

bustupbiker · Oct 31, 2007

terayon said:
you can't call them overhead cams as there not actually "overhead"

You could almost call um side valve :blast

dronning · Nov 1, 2007

terayon said:
definition. (DOHC) An engine with two camshafts located above the cylinders. One drives the intake valves and the other operates the exhaust valve.

notice the use of Above or Overhead, on a flat twin everything is mounted on the side. BMW only state twin cam, I've not seen them use the term "Overhead" yet. Even Ducati just use the term "twincam" as one of theirs is on the horizontal level.

The term overhead can be used because they are overhead as defined from the crankshaft centerline - NOT the center of earth.

A dual overhead camshaft (also called DOHC, double overhead cam, dual overhead cam, or twin cam) valve train layout is characterized by two camshafts being located within the cylinder head, where there are separate camshafts for inlet and exhaust valves.

Same rule applies when defining overhead valves on a radial engine. They aren't just "overhead valves" on the top cylinders.

Dave

Dahoum · Nov 1, 2007

I do love it when we get a good technical debate in the technical section :rob

Brian ROSEN · Nov 1, 2007

Fact or fiction

What is this about a new 1200S ? I note that the drawing is labelled K1200S - but obviously it is a boxer twin. Should I have heard about a new model, even though I am not in the UK (nor germany

Damir · Nov 2, 2007

It is new R1200S HP2 introduced in Paris few weeks ago.

Brian ROSEN · Nov 2, 2007

Wow

How did I miss that! Presumably we can expect a new Boxer cup?

terayon · Nov 2, 2007

No they will be spending all their money and time on WSB 2009

Shep · Nov 2, 2007

Two questions, how will the valve clearances be adjusted? And is it still a twin spark?

Shep

dronning · Nov 2, 2007

It's single spark plug, no need for dual plugs with this head design. The valves are adjusted with shims - not 100% on the type of shim but I'd guess it's a bucket shim.

Dave

Shep · Nov 3, 2007

dronning said:
The valves are adjusted with shims - not 100% on the type of shim but I'd guess it's a bucket shim.

Dave

I guess the drawings are an artist impression then, no shim bucket appears to be shown :nenau

Shep

Deleted account 211025001 · Nov 3, 2007

I felt silly asking this before so didn't

but, Shep's question has raised it again, so, here goes:

The OHC design shown clearly shows the cam acting upon a rocker which then acts upon the valve stem.

If the problem MWB have had in the past with OHC designs is excessive cylinder height (engine sticks out too much) then why the rockers.
Surely a cam acting directly onto the valve stem (with buckets) would be shorter (or maybe not) :nenau

Can anybody explain please?

Andres

PS Droning, do you care to elaborate upon why this valve arrangement does not need dual spark please :nenau

st247 · Nov 3, 2007

Outtomunch said:
The OHC design shown clearly shows the cam acting upon a rocker which then acts upon the valve stem.

If the problem MWB have had in the past with OHC designs is excessive cylinder height (engine sticks out too much) then why the rockers.
Surely a cam acting directly onto the valve stem (with buckets) would be shorter (or maybe not)

Can anybody explain please?

Looks like the valves are set radially in the head and the cam lobes are angled (red circles), as are the rocker shafts (green line) compared to the camshafts. So i'd imagine it's to do with that. Still can't see any adjustment though :nenau

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