Oil leak from head cb650c

[jake650]

Having to rebuild top end to cure an oil leak.
Suspect previous owner tried same but used wrong o rings.

I have bought a full gasket kit from David silvers  but told the kits rings are too small because not same size as original asbestos ones that are no longer sold

Anyone know the size I need or better can provide a source for correct size.

Reckon I'll be a frequent flyer on this forum as last engine I split was a super dream 35yrs ago. Not looking forward to it.

Manual and torque wrench at the ready, any tips appreciated lol.

I'm in UK

[McCabe-Thiele (Ted)]

Yes this is a common issue with modern head gaskets being a different thickness than the originals so a different thickness 'O' ring is required to ensure a good oil seal. It appears that some manufactureres of aftermarket parts have not changed the 'O' ring size to compensate.

I'm pretty sure someone here will be able to assist you with what sized 'O' rings you will need - have you tried asking DS if they have made any changes - they can be helpfull if you get throught to someone experienced in the parts sales section?

[SteveW]

Check out my thread on the subject. 1500 miles later and no leaks at all.

http://www.sohc.co.uk/index.php/topic,28673.msg270381.html#msg270381

[Bryanj]

Carefully measure the id of the O ring and the thickness then try for a viton one that is thicker in cross section.
I have the sizes for the 500 and 550 but 650 parts list never gave sizes

[Bryanj]

Just checked on cmsnl (a good reference) and the O ring part number is a 500 four one so use the suggestion given