RCU Forums - OS 40 SF

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Texas Don

10-07-2011 10:36 AM

OS 40 SF

Iwas fortunate to find one of these in fairly good condition. The engine shows evidence of light use and was treated with after run oil. When removing the back plate to inspect the crankcase, of course I tore the paper gasket. I've found out that the back plate gasket from a 40 FX fits perfectly. What Ineed is a head gasket. I understand that this engine is long out of production so Imay have to make one. Will a head gasket from any other OSmodel fit this engine?
Thanks,
Don

Bax	10-10-2011 06:45 AM

RE: OS 40 SF

We don't have any list of parts that cross from one engine to another. You can try and see. You can also make a head gasket from .004"-.007" brass or aluminum shim stock. Before you do, though, please make sure you really still have the original cylinder head gasket. O.S. uses aluminum, and it looks like there's nothing there when you remove the cylinder head. If the groove it should be in is smooth, it's there. Look closely. You'll normally see some mold marks if the gasket isn't there. We remove them by carefully prying them up with the point of a #11 blade or a fine pin or needle.

Raymac

10-12-2011 09:16 PM

RE: OS 40 SF

I have what I think you are looking for....It is OS part no. 23364000 for 40FP and 40FP-S.
It measures .840" X 1.00" backplate gasket too. Nw in package. $5.00 dselivered.

Bax	10-13-2011 06:02 AM

RE: OS 40 SF

That part is for a .40 FP and won't likely fit the .40 FX.

Texas Don

10-13-2011 07:04 AM

RE: OS 40 SF

Quote:

ORIGINAL: Raymac

I have what I think you are looking for....It is OS part no. 23364000 for 40FP and 40FP-S.
It measures .840" X 1.00" backplate gasket too. Nw in package. $5.00 dselivered.

It won't work. I have an OS40 SF which needs a head gasket of .805 or 20.5mm diameter. The OS40 FP gasket is too large. I have found though that a Thunder Tiger 40 Pro has a head gasket of 20.5mm. I've ordered one of those to see if it fits.

Texas Don

10-13-2011 07:09 AM

RE: OS 40 SF

Quote:

ORIGINAL: Bax

We don't have any list of parts that cross from one engine to another. You can try and see. You can also make a head gasket from .004"-.007" brass or aluminum shim stock. Before you do, though, please make sure you really still have the original cylinder head gasket. O.S. uses aluminum, and it looks like there's nothing there when you remove the cylinder head. If the groove it should be in is smooth, it's there. Look closely. You'll normally see some mold marks if the gasket isn't there. We remove them by carefully prying them up with the point of a #11 blade or a fine pin or needle.

Thanks for your reply. I suspect that the head gasket has been replaced before now. The current head gasket is brass. I won't attempt to remove it until Ihave a replacement in hand or have exhausted all avenues of finding one.

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