O ring - getting it right

Is there an eaasy way to ensure the O ring is seated properly when refitting the breather cap on the cylinder head?

The bit I am talking about is part number 874521 description Breather cover cpl

I did not find that part #. Do you mean the cover over cam gear on back of head?

yes, that's correct

I use a dab of real sticky syn grease or a spot of black rtv.

There are two different designs for the breather plate and two different o-rings depending on which one you have.

Early motors just use a very thin section ring that crushes into a taper in the face of the orifice in the head. Later versions the cap has a groove machined n the spigot of the cap that a fatter o-ring sits in.

On the early heads that use the first system the orifice in the head has a stepped tunnel. On later heads the tunnel is a parallel sided bore. The later breather plate covers won't fit into the early heads.

If you have the correct o-ring for your head and breather plate design there should be no problem with fitting. If you are trying to use a fat, later type, o-ring on an early plate it won't crush down properly and if you are using an early o-ring on a later plate it will be too large and too thin to fit in the groove properly.

Pete, that's interesting to know, I have usually gone and ordered what has been listed on the parts site and the parts manual.

I do recall that I had some sort of O ring band installed and the replacements were O rings.

Do you happen to know the part number for the early heads please?

thanks

Early oring is #976584. I thought you were referring to the late one w/groove.

I am pretty sure I have the stepped head and a groove on the cap, I shall be checking again shortly so can feed back.

Thank you for the p/no I took a look and it is O-ring 44.17X1.78mm the ones I get are O-ring 47,35X1,78

Late ones are P/N # 880965 2.62 X 46.52 fits in groove