cylinder "o" ring,part No. 40/1299

[motson]

Hello all,
I am new to this forum as i have just acquired a 40 Featherweight Seagull (ref F 552 F2) & i am currently in the process of rebuilding the head unit after cleaning out a corroded cylinder block.
I am a little confused about a part which is shown on the exploded diagram in the owners spares book,namely item No.23 (cylinder "o" ring),part No. 40/1299.Can anyone tell me where this o-ring is supposed to be fitted as the diagram isn't too clear on this point-it is shown as though it fits somewhere on the head,& by it's orientation on the drawing,as though it goes on the block exhaust outlet but i don't recall there being an o-ring on the exhaust outlet when i stripped it down?
Can anyone please enlighten me!?
I could be writing utter nonsense so please bear with me...

[Vic]

Interesting.
I agree the parts diagrams indicate that it fits on the exhaust outlet but is part no S/1299 in my book.
however I cannot find it listed in the book that came with my 40+ (no diagrams of the power head in that book) which is a year older.

Both my engines are younger than yours. Mine are '74 and '73. F 306 DD4 and FP 558 EE3

Is your parts book original or later. I'm wondering if the O ring was something added between 73 and 74.

If you had the O ring could you fit it? If not forget it.

[40TPI]

This picture is one of a series for a strip and rebuild of a Forty Plus showing the the wire-locking of the water pipe union nut, however the silicon rubber O ring can be seen fitted in the annular slot around the exhaust port. (The Forty Plus and Featherweight share the same 64cc block.)


Click on thumbnail to enlarge.........

Is it needed? Most would agree that it makes no discernible difference to exhaust noise and little difference to the amount of unburnt oil and gloop that leaks out from the exhaust/block joint, especially when the exhaust tube has become slightly bell mouthed after frequent dismantling.

Peter

[Vic]

I reckon the photo answers the question. If theres a groove for the O ring then fit it. If there isn't then you can't!

[motson]

Many thanks for your replies,i was just a little worried that the "o" ring may have been an oval profile copper affair that somehow fitted in with the copper head gasket & was there to ensure a good seal once the copper gasket tightened on to it.
That's great then,i will continue rebuilding the head safe in the knowledge i haven't left any seals out which should be there!!
My exhaust port doesn't have the annular slot in it so i cannot fit it anyway !
For info,vic,the owners spares book (+service manual & owners handbook) were recently purchased from Sheridan Marine.

Cheers
Martyn

[Vic]

For info,vic,the owners spares book (+service manual & owners handbook) were recently purchased

Old engine, new books. That is what i expected. Supports my theory that the O ring was probably introduced in or around 1974.

I go a pull my two apart to see if one has an O ring and the other doesn't

[John@sos]

For earlier motors that will inevitably leak oily gloop at the top of the tube, next time you strip it down clean off the inside of the tube and the block, then refit with a liberal coating of RTV, the heat proof silicone sealant.

works with the later ones too!

Regards,
John
SOS, all the parts here, including the books!