more on other expansion chambers used on Konigs
Tim:
If you will access a thread on BRF called "An Amazing Story" by Wayne Baldwin, you will find photos and more information on the expansion chambers built by Harry Pasturczak for the 4 cyl rotary valve Konigs. As I mentioned, these were in use prior to Dieter sending engines to the US with the sliding expansion chambers you are familiar with. I think your thoughts regards cost versus staying with the competition are right on the money about why he chose this particular time frame to put the chambers with the motors. He had no reason to do it from a competition standpoint, it was extra cost, so he just didn't. He had enjoyed for several years, prior to the other chambers made by ZAK, dominance in most of the classes the Konigs competed in, as the primary competition, Quincy Flatheads had reached a plateau in development a couple of years before, and except for the rare occasion, were not much of a threat to win. That left only the Konigs that were being modified further by folks here in the US like ZAK with pipes, different rotary valve discs, etc., to cause any problem with winning over the "stock" factory Konig. These did not slide (except for the stinger and mid section in later models) and were made so as to accept the exhaust from both top cylinders into one chamber and both bottom cylinders into another as they both fired together, and Harry felt based on information availiable at the time that was the best way to combine the exhaust pulse, instead of two cylinders firing 180 apart into one chamber. This for a year or so, until the sliding chambers put on by Dieter, was far better than the "tin can" type silencer, but sliding them presented a problem because of that type design. Just about the time ZAK figured out how he was going to do that, Dieter changed the spacing on the exhaust ports (closer together on the square block) and that made the casting patterns Harry had for the manifold/collectors obsolete. At that point he took that action by Dieter somewhat personally as it was going to cost a lot of money to make new patterns, and he ceased further development on his pipes. I am sure you will find it interesting if you have not seen it.
In looking at the information/thread that Peer started again, I notice that Carlo Verona has made a post that he is (at that time/2007) building 10 copies of the engines that were used in the GP bikes. I have no information as to whether that project was ever completed. Carlo is the mfr of the VRP racing engines and you could probably contact him by accessing his web site. Probably just "Google" VRP engines.
Ralph Donald is a very good friend of mine and I will forward your request for contact to him so he will know of your interest in contacting him. We have two boat races over the next two weekends here in the US that I know he is planning on attending, so it may be after that before he has an opportunity to contact you, but I will be sure to let him know you wish to visit with him about whatever knowledge he may have regards this.