Boxerworks.com

I have a 73 R90. I bought the bike, I trusted what the seller told me, it was a mistake. Right side cylinder and piston are trash. Chances of finding a correct cylinder and piston are slim these days. I bought a real nice cylinder and piston on ebay. It doesn't fit. After doing some research, i could have the cylinder i bought turned down at a machine shop, the cylinder isn't physically the same, short a inch on the width. If i did that and ever wanted to sell the bike, that could be a problem. The bike wouldn't be correct.
Looks like my only option is to keep searching for correct piston and cylinder, or part it out.
I was wonder what you all think?
Thanks!

Officially, the R90 series (R90/6, R90s) started in 1974, but production DID start in the fall of '73. Was yours made then?

The chance of finding parts, cylinders is not slim. Several online retailers have used parts.

It really depends what you want the machine for. If it's as an investment then the exact parts matter, if it's as a machine to ride and enjoy then provided they work, they don't (matter that is).

To my mind, the whole 'absolutely original' thing is a crock anyway. Any machine that is over 40 years old is going to have parts that have been changed. In any case, if you were to go to BMW say 20 years after the bike was made, the parts you would get probably wouldn't be the same as the oines that were on the bike when it rolled of the line. Very possibly, the replacement part will be better than the original anyway.

Yes, it is a mistake to trust what a vendor says in the case of a vehicle of this age. Almost everyone has a tendency to have selective amnesia when they are anxious to sell... unless, of course the vendor is a business and has made guarantees. You have to accept, when you buy, that you take a risk and there may (will) be things that need attention. Learn all you can about the machine before you buy and ask a lot of questions. I don't know how your cylinder was 'trashed' but if it's going to affect running, then likely it would have been detectable by a compression test.

As RPG90s says, R90 parts are around and you should be able to track them down without any problem.

In my opinion, you have several options...

1) Put the parts you've got on the bike and ride it.
2) Keep the bike and source the necessary parts to restore it the way you want it.
3) Put the parts you've got on the bike and ride it keeping an eye out for the 'right' bits so that you can bring it back to 'original' at a later date.
4) Bite the bullet, decide you don't want the bike and flog it as it stands, using the money you get towards a more pristine machine.
5) Part the bike out... but bear in mind that involves a good deal of work and you will probably be left with a lot of parts that aren't required.

The answer depends on what you want from the machine, how much work (and what kind of work) you are willing to put in and how much you are willing to invest.

Rob