Appears to be a round oil filter cover on ebay

[Steve Swan]

http://www.ebay.com/itm/1969-HONDA-CB750-SANDCAST-ROUND-OIL-FILTER-CANNISTER-/250934566956?hash=item3a6cdda02c&item=250934566956&pt=Motorcycles_Parts_Accessories&vxp=mtr

[Wayne]

I do believe that would have come off of 810 as it was not on the bike when the buyer from California bought it. It had been replaced with a finned cover.

[kp]

I don't know the answer to this question. Is that a real sandcast original fin-less cover 

[markb]

Comparing it to the one I have, it looks authentic to me.  The outside corner is much more rounded than a finned cover thats been turned down.  And there is no evidence that the inside has been machined.  I'm interested as to what the experts think.
Mark 

[Steve Swan]

i saw it and at very first had unfounded suspicion, the outside looks kind of rough, but the inside look like Mark said.  Damn experts, even if they did show up, they probably would say it was a cup with a hole in the bottom.

[kp]

My understanding is that these covers are cast alloy with a sandcast finish on the inside with a smooth finish on the outside, a somilar finish to the polished covers? Because I don't own one it is always hard to know what is what. KP

[Wayne]

Well, I'm no expert but the guy who owned 810 and was turning it into a Cafe' had no idea what a "sandcast" CB750 was, that is why the round oil filter was still on the bike. He told me it had been on the bike as long as he remembered. Doesn't really confirm fake or real but it does confirm the owner of 810 didn't fake it as shown in the pic or as he drove the bike previously.

[hondasan]

Pretty sure that is the real thing - sandcast finish inside is the give away. External finish? - should be polished / clear coat as per the other engine side covers, based on what was on #302 (pictures attached hopefully). Or maybe external finish varied?

Cheers - Chris R.