Boxerworks.com

Mmmmm. Thanks Rob. When I bought the engine, the guy said it was from a bad drop with no damage to the motor, but he had no idea of its history. I'll check with Mr Vernier this morning. Though I have had a sneaking suspicion this may have been the case. Is there any indication through engine numbers, bearing in mind this is an r75/5 frame

That's if the engine is an original whole unit. After I posted previous, I realised they may be an add on over the years. Most of the bikes parts I have added are /6 and /7.

The frame number isn't any help because the engine isn't original to the frame, however, on a '78 machine the engine number should be identical to the frame number. Putting that number into an old BMW Parts ordering program or RealOEM should give you an indication exactly what the original donor bike was. It should also tell you what parts were fitted but I have suspicions that this isn't completely reliable. In this particular instance, it's more problematical because the 40mm headers came into use around '78/'79 but their introduction wasn't uniform... the introduction dates (and withdrawal dates for that matter) differ depending on territory. Even within the period, not all 1000cc engines were fitted with the bigger headers. As best I can tell, I think there is a good chance that a '78 motor from a 'S. 'RS or 'CS may well have started out with 40mm headers... but, as you so rightly say, who knows if the cylinders are original to the engine.

What I guess I'm saying at the end of the day is that the only reliable guide is the internal vernier... in the long run, the important thing is what you have in front of you not what may or may not have happened in the dim and distant past.

Rob