I bought this gasket kit for my CB500 off of ebay:
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=380321765572This seems to be one of the most common kits available for the 500. None of the o-rings were labeled or separated at all, and there wasn't any kind of inventory list, either. So, I compiled a complete list of o-rings that are listed in the parts manual and I marked the ones that were included in the kit. Just thought this might be helpful to share.
+ (12x) 30.8mm o-rings:
-8x valve tappet covers
-4x carb manifolds to engine
+ (3x) 11x2.5mm o-rings:
-1x tach drive
-2x base gasket pegs
+ (4x) 6x3mm o-rings:
-4x cylinder head side cover studs
+ (8x) 10x1.6mm o-rings:
-8x under valve guides
+ (2x) 5x2.4 mm o-rings:
-2x oil passages through head gasket
+ (4x) 61.8x2mm o-rings:
-4x under cylinders
+ (1x) 5.8x1.9mm o-rings:
-1x Cam chain tensioner adjustment nut
(Kit included one extra of this o-ring for some reason)
(1x) 15x2.5mm o-rings:
-1x Oil filter bolt
(1x) 89x4.5 o-rings:
-1x Oil filter bowl
(1x) 23mm o-rings:
-1x Oil dipstick
(1x) 24.4x3.1mm o-rings:
-1x Engine starter motor
+ (2x) 14mm o-rings:
-2x oil pump passages
+ (1x) 47mm o-rings:
-1x oil pump
(1x) 19.4.x2.8mm o-rings:
-1x under oil pump cap
+ (1x) 24.5mm o-rings:
-1x on final driveshaft under large bearing
+ (1x) 11.5x2mm o-rings:
-1x on shift fork drum under lockwasher
+ (3x) 19.4x2.8mm o-rings:
-3x oil caps on bottom case and right side under points
(Kit included 4 of these o-rings, 1 more than the necessary 3)
(1x) 13x2.5mm o-rings:
-1x under left hand oil cap under generator
The kit also included the 4 exhaust crush washers, 6 rubber pucks, head gasket, base gasket, clutch cover gasket, points cover gasket, alternator cover gasket, starter cover gasket, oil pan gasket, valve cover gasket, and breather cover gasket.
All items marked with a + were included; those not marked were not. The only indication of brand is a small white slip of paper that says "GASKET SET
HONDA
CB500/K1-3
MADE IN JAPAN"
For $70, I'm glad that this kit included at least the vast majority of everything I should need. However, I don't know why they would include the 24.5mm o-ring (Part number 91306-703-000) for the bearing on the final countershaft in the transmission. I tore all the gears off of that shaft, but I couldn't do anything to get that bearing to budge. The bearing runs smooth and everything seems ok, so I'm not too worried about replacing it.
Anyways, I hope this inventory could help anyone looking into one of these kits. I know it would have helped me!
