I am looking at taking the best of four cylinders and pistons to make the best one motor possible.
Two of the cylinders have an "A" stamped on the outside of the cylinder liner. The other two have a "B" stamped on them. I thought for sure I read somewhere what this meant (if anything), but I can no longer find this reference.
Any ideas?
I am pretty sure that the 82 cylinders were shorter with a thick head gasket while the 83's had a taller cylinder and thin head gasket. Can you get a measurement from the surface of the base gasket to the head gasket and see if that may be the case.
If one were to run 82 cylinders with the thin gaskets would a beneficial rise in the compression ratio be realized?
Part numbers for the head gaskets, 82 and 83 are the same. Most likely It is the class size of the standard bore. A,B,C etc. The markings on the pistons are probably long gone. If the cylinders have been bored it doesn't matter.
If you think one set of cylinders are taller, measure them and see.
1983 XZ550 head gasket 28V-11181-00-00
1982 xz550 head gasket 11H-11181-04-00
I have always thought that would be an easy way to increase compression. Shorter cylinders and thinner gaskets.
I'm a bit skeptical of a cylinder height difference between the two years if for no other reason then tooling costs. Admittedly, there may have been a very good reason making it a necessity that I'm simply unaware of. It would be interesting if accurate measurements could be found of the two jugs.
Different head gaskets on the other hand seems more reasonable although doesn't necessarily mean a difference in thickness. But again, a side by side comparison of NOS parts could answer that question.
Re: thinner gaskets/increased compression.... Who was it that found a vendor that made solid copper head gaskets for the Vision? Did they end up being slightly thinner or thicker than stock? Muck like a worn chain, this might alter valve timing a bit so keep that in mind.
Looks like Motoracer8 has the best answer. I'd never heard of this before.
Below is a thread from another Yamaha bike forum. My guess is the methodology is consistent among Yamaha. It basically shows that A-D markings were used to match parts that were within the overall tolerance, but match even more closely by matching parts down to several sizes in the 1/10,000 range.
http://dirtrider.net/forums3/threads/yamaha-cylinders-a-b-c-d.38768/page-2
Thanks again!