BMW R1200RT '07 (K26) engine swap compatibility with BMW R1200ST (K28)

[rozario]

Hi all,

One of the timing chain guide rail broke in my '07 RT. The engine block is clocking 120.000km and I am thinking about swapping it by another one instead of changing the guide rail (which would require a huge amount of work and tools I don't have).
I found a second hand engine block from a 1200 ST with very low mileage at a decent price. From the BMW parts catalogue, the engine block is common and shares the same reference between the K25 ('07 - '10 GS), the K26 ('04 - '10 RT) and the K28 ('03 - '07 ST).
My question is simple, are these engine blocks similar? Do you think that I could just swap these without any hassle?
Also, my bike has an on-board computer with an oil level switch sensor. In the case the engine I purchase is from a bike without on-board computer, do you think the sensor can be transferred from the old to the new block or is it completely sealed off?

Thank you very much for reading and replying to my questions.
Ride Safe
Rozario

 

[dbrick]

If the BMW parts fiche (such as found on real oem.com, or on the websites of many US BMW dealers) shows the same BMW part number for the engine block on the two bikes, then the parts should be identical.

The ST block should have a tapped hole for the sensor, either available for use (if the ST was so equipped) or with a removable plug if the ST lacked the sensor.

While I wouldn't say a block swap would be "without any hassle," it should merely be a matter of wrench-twisting. Good luck!

 

[rozario]

Hi, thanks for the answer!
The parts catalog on bmwmotorcycles.com and on realoem.com state the complete engine is suitable for both the RT and the ST (see attached screenshots). I also checked and if I look for a complete engine for the ST or the RT I end up to the same part number. So I think that it should be good.

Thanks for the sensor, that was what I was hoping for.

And yes, it is not going to be an easy job but, as long as I have to take the engine out, I'd rather "just" swap it with a more recent one instead of completely tearing it apart.

 

[dbrick]

Rozario,

Let's slow down a little here.

Your first post talked about obtaining an engine block from an ST to replace the damaged one on your RT. Here in the US, the word "block" refers to the large housing (sometimes in two pieces) in which the engine internals (crankshaft, pistons, oil pump) are mounted; this is sometimes here called the "crankcase." BMW calls this the "engine housing."

My answer assumed that when you said "the engine block is common" you meant that the part numbers for what we call the block or crankcase or engine housing were the same in your RT and your proposed donor ST. If that were so, then the parts themselves would be the same, or would be easily interchanged (as by removing a plug in a tapped hole).

But in your post just now you use the words complete engine. A complete engine is somewhat more than an engine block, because the complete engine also contains cylinder heads and valves and so on. I looked at the realoem.com fiche, and see that there are two different part numbers, one for a motor with an oil leveling switch, and one for a motor that does not have the switch.

I do not know what the differences will be between the motors you're considering. Without knowing the original equipment of the ST from which the motor came, it may not be possible to know if the ST motor will work as a drop-in in your RT, or if some additional work or modification will be necessary. If you have the VIN from the ST, you may be able to discover through on-line resources how the ST was originally equipped at manufacture, and whether the ST's complete engine would bear the same part number as the RT.

I'll guess that this engine change is a do-able job by a home mechanic, but I do not know.

Good luck!

 

[rozario]

Thanks David for checking this up, that is of great help to me.

You were right, I was referring to a complete engine and not just a crankcase.
I find it weird that despise the fact that there are two different references for engine housing (one with and without oil level switch), there is just one common reference for a complete engine. Do you think that BMW would cast two different crankcases just for an oil level switch?
Beside that oil level switch, what could be different due to the bike original equipment? I do not think that they are any other optional engine sensors?
I will try to get the ST's VIN.
Thanks again

 

[dbrick]

Thanks David for checking this up, that is of great help to me.

You're welcome!

You were right, I was referring to a complete engine and not just a crankcase.
I find it weird that despise the fact that there are two different references for engine housing (one with and without oil level switch), there is just one common reference for a complete engine. Do you think that BMW would cast two different crankcases just for an oil level switch?

It seems really unlikely to me that BMW would cast two different crankcases. I think it'd make more sense to drill and tap all the blocks, then put a simple plug in the parts that'll be used on bikes without the switch. But I'm theorizing here as well, and don't know if this is what BMW has actually done.

Beside that oil level switch, what could be different due to the bike original equipment? I do not think that they are any other optional engine sensors?

Darned if I know. The parts fiche suggests to me that the sensor is the only bit that differentiates the two motors.