R65 cylinder heads. Looking for identification

[wilcom]

A search of eBay international sellers does not have any at reasonable prices

I saw these here locally, if you were going to rebuild a set of heads after you bought them this price for the pair doesn't sound too bad......
https://www.ebay.com/itm/BMW-R65-Airhead-Cylinder-Heads-Remanufactured/112991414382?hash=item1a4ed0286e:g:HHwAAOSwPapa-HoR:sc:ShippingMethodStandard!92584!US!-1:rk:77:pf:0

[georgesgiralt]

So I inquired to the local Guru.
My two heads are from the later bikes (we could bet on it as they have the exhaust fresh gas port).
One is from a de-rated R65 (similar to the pre -1981 models) without squish bands and small valves. This one has been modified to have 8 mm stem valves from an R50/R60 (hence the 8 mm diameter guides)
The other one is for a 50BhP R65 with big valves for a post 1981 model, so will fit my bike. It has 7 mm stem valves of the big diameter.
i can't buy refurbished heads because i already have everything to renew the heads. This is why I bought those ....
Mystery solved.
If someone need a head for an old R65, call in   8-)

[Tony Smith]

So I inquired to the local Guru.
My two heads are from the later bikes (we could bet on it as they have the exhaust fresh gas port).
One is from a de-rated R65 (similar to the pre -1981 models) without squish bands and small valves. This one has been modified to have 8 mm stem valves from an R50/R60 (hence the 8 mm diameter guides)
The other one is for a 50BhP R65 with big valves for a post 1981 model, so will fit my bike. It has 7 mm stem valves of the big diameter.
i can't buy refurbished heads because i already have everything to renew the heads. This is why I bought those ....
Mystery solved.
If someone need a head for an old R65, call in   8-)

In my view the mystery has deepened.

Putting aside for the moment the mis-characterisation of the machining on some cylinder heads as being "squish band" - it isn't, the squish band is the gap between the cylinder head and the outer edge of the piston, my "mystery' is the (apparently) German market only de-rated version of the R65.

My understanding from the (admittedly limited but actual BMW literature) material I have is that the de-rated, Germany only  R65 was de-rated by fitted 26 or 28mm carbs (the confusion being that both sizes are mentioned int he documents in different places - I suspect 28mm is correct).

No other modifications for the de-rated version are stated although I do admit that simply continuing the valve sizes of the Pre-81 model would also contribute to the effective de-rating of the engine.

But, I stand by my previous statement that I simply do not believe that BMW would set themselves up for multiple spare parts supply chains to achieve so little.

There is simply so much myth and mythology surrounding some aspects of BMWs I find it very difficult to navigate.

That said, clearly the o/p has in his hands an apparently post 81 cylinder head with small valves.

Does anyone actually have definitive information on the de-rated R65 rather than the peripheral mention it gets in the service bulletins I have?.

My next question is that I thought that the air-port cylinder heads were only ever fitted to USA destined models, obviously that belief is wrong if in fact they were fitted to European models.

It is really only curiosity as nothing of any importance turns on it.

[mrclubike]

Maybe the heads were all machined with the smog ports but were plugged in markets that it was not required 

[georgesgiralt]

After 1986, all European model had exhaust ait-ports. And the matching tubing to the air filter box.
26 mm carbs where only fitted on R45 (according to my 1982 maintenance manual for the R45~R65) And 28 mm carbs where fitted on 26 BHP R65 we never saw in France as it seems it was a German and Greece learner bike...
This last statement does not come from literature but from a discussion with the local Guru.
Anyway, one of my heads is for sale or exchange ...

[Barry]

Standard 35hp R45's have 28mm carbs. 27 HP R45's have 26mm carbs together with lower compression and a softer 284 cam.  The 27HP R65 had an even softer 256 cam and according to Bing.de it also had 26mm carbs.