UPDATE as of 2-26-03

After seeing an adapter plate for a 750 go on ebay for $183.50, I decided that spending $79.95 at cyclexchange.net wasn't such a horrible prospect. They told me the plates O.D. was 4", which does match the stock housing. The plate attaches to the block with a hollow bolt, and you use your stock length bolt and housing to attach to the plate. They must have rushed it because it only took one day to get here, and the verdict...........It works. Perfectly. I figured the oil filter bolt and threads on the engine block would be the same on the 650 as the 750, (also the 550) and it turned out I was right. So, I bought a used oil cooler from a '82 CB900 and will be fabricating the bracket for that soon. I'll leave up the below ideas in case anyone is interested in making their own.

Below are other ideas the have been mentioned on the greenspun message board:

• Adapter plate from '83 CB650SCC Nighthawk: Would probably need to fabricate a longer oil filter bolt, or possibly use the bolt and housing from the '83 one as well, if it would thread into our block. Also, I was told by Rick D. on the greenspun board that, "The oil cooler adapter plate from the 650/750 Nighthawks will not fit a CB400-f for sure, so I doubt if it will fit one of the other SOHC motors. The casting that the oil filter bolt screws into protrudes too far and hits the center section of the plate before the outer gasket area seals to the crankcases. It's not even close, something like .25" away. You may be able to machine the adapter to fit, but I haven't got around to trying that yet."
• Configuring the oil filter housing with an inlet/outlet. This has been mentioned, but I can't see it working. The adapter plate pretty much just blocks the oil from reaching the filter, pumps it to the cooler and then into the housing. You'd have to somehow tap into the bolt, feed it to the cooler and then get the oil back into the engine... Ok, lets just go with the adapter plate idea :-\
• Earls Performance Products used to sell the plate, but have informed me that it is discontinued.

Below are the plans from the MotoTherapy web site, designed for the CB750. Would be possible, but hard to make the extension bolt. He bought this one on eBay, it was definitely produced for mass sale at one time but I don't know what company. Like I said above, there are other style adapters that use the stock bolt length, unlike this one.

This one I saw on Ebay, but it caught my eye and I'm glad it did. I was thinking about how to mount my CB900 oil cooler, (same one as pictured on the left), and I saw how easy it can be fabricated for my 650. I don't know if this is how they came, but in the picture it looks like a simple pipe or conduit bracket that attaches to the front frame area, bolted to another small piece of metal that connects to the cooler, allowing it to be adjustable for any bike.