Crankcase gasket ???

[PatLNR]

I'm trying to restore a Forty Plus (1969) and I 'have a little problem.
On this Seagull ,there is a crankcase gasket..
It's possible that this engine was rebuilt in the factory ???
The silencer tube is also in chromed stell ???

[Keith.P]

Cylinder base gasket, yes, crank case gasket no, not that I have ever seen.
Aluminium, or chromed brass exhaust, not steel, sounds like its had someone playing with it, a 1979 I suspect should have an aluminium exhaust.
It should all be fixed quite easily.

[PatLNR]

Yes I never see a crankcase gasket before...
But , why there is a gasket...?
Bad waterproofing after disassembly ?
I don't know what is the best : leave the gasket in place or remove ?
The Seagull starts without problem and no leakage.

[Keith.P]

See how much end float you have in the crank, if you have a little, remove the gasket and use a small amount of gasket sealer.
Maybe it leaked before, or maybe it had no end float, or the previous owner didn't know any better, I would pull it apart to see what else has been done and do it right.

[Collector Inspector]

There is no crankase gasket.

If one is there throw it away and lap cases flat and with case sealant put back together tight.

Send a pic of what you have.

We love Pics!

B

[PatLNR]

Yes I also like pictures.

There is a gasket !! but why ??

[Gannet]

I have a 1951 FV, which on stripping the crankcase there was a gasket between the faces. The curious aspect was that it appeared to be a 'professionally' produced one. It is a very difficult profile for a scissors job and It had been very accurately produced. Whether it had been fitted by BS at initial build or sometime since, I have no idea.

It doesn't stike me as a good idea. It is better, I am sure, to create the seal by using lapped surfaces with a smidgen of sealant, which is what I will do on rebuild.

The only slight doubt in my mind is whether a gasket (with a layer of sealant either side) allows a slightly greater degree of movement between the crankcases whilst still retain a leak tight seal. The stub tiller on the FV/FVPs does provide a very convenient handle with which to lift and carry the engine. The resultant stress on the top crankcase will tend to lift it off the lower crankcase or certainly reduce the clamping force in the area of the joint by the stub handle.
This did appear to be a problem to BS. Early on, (at about serial number 2000), the top crankcase casting was stiffened up by the addition of a web just above the stub. This would certainly have helped to prevent crankcase leakage at that point.

Jeremy

[Keith.P]

From the pictures it looks to me more like a thick paste than a gasket.
More unprofessional than professional.

[Collector Inspector]

No gasket "material" ever. I see no actual part listing for one FV.....................I may be incorrect in my reference however...........never know aye.

Just "sealed" with either basic paint or nicely done machine work........maybe some varnish/shilack if that was costed as a production thing back then.

I would just assemble as I mentioned above and be done with this issue aye?

A sealed case is a good case for commissioning a running motor point blank.

The rest of the issues are dealt with from that if a "No Go Situation" remains.

B

[headdownarseup]

One or two of my old 102's (pre 1950) have had a gasket between the case halves.
As KEITH and BRUCE suggest, when the crankcase is reassembled, check how much "end float" there is at the crankshaft (up/down on the flywheel)
There should be some movement, it varies a LOT between motors.
Put the engine back together, if it's making funny noises when spinning the flywheel you know something isn't right.
Clearance to the underside of the flywheel rubbing against the points box/cover can sometimes be evidence of this.
Try it and see how it goes?

jon

[Charles uk]

I have worked on every model of Seagull from the start (1932) to the finish (1994) & never have seen any model that required a gasket between the 2 crankcase halves, if anything fitting this type of gasket will lower the position of the flywheel & might increase uneven conrod wear.

Seagulls always had a lot of crankshaft end float up to 4mm in the worst cases & I've never heard of it causing any problems.

Remove the gasket, if the faces have any obvious lumps & bumps, lightly sand with wet fine 400 or finer, wet & dry until the high spots have gone, you don't have to sand until the low spots have disapeared & use any sealer that your local car parts shop suggest, there is so little crankcase compression (max 5lbs) & it should be fine.

I always use RTV & have had no problems with it.

[headdownarseup]

CHARLES, you've been lucky!

Myself and JEREMY have rebuilt 40's and 102's (old ones at that) with a gasket in between the case halves. Not all, just the odd one or two.

Odd, i agree. It's not normal for BS to put motors together that ALWAYS required a gasket, but you never know? (stranger things have happened)

jon

[Horsley-Anarak]

I have taken a few apart, have never seen a crankcase gasket, none of mine have them.

Have had quite a few with leaking crankcases next to tiller stub, due to falling over damage I suspect.

Crankcase gasket is not listed as a spare part, could see it would be a simple fix for a factory re-ferb.

If the gaskets are machine cut, it must surely be a factory fit?

H-A

[Charles uk]

This gasket does not appear in any of the price or part lists & if not fitted carefully could lead to a slight loss of crankcase compression.

It would possibly require the cylinder retaining studd holes to be at slightly different positions, it just sounds like they were reassembled by someone who thought it needed one.

The only justification I can think of for Seagull fitting them, would be so that they could use crankcases that were slightly out of tolerance.

[PatLNR]

Many thanks for all your answers.
Mea culpa ,me maxima culpa....It's not a gasket but a strange heavy past...
I have rebuilt the crankase after a good cleaning and with silicone motor sealant.
I hope that will be good.
Many thanks for your help.