New rebuild engine problem

[ducati2242]

Putting a centre gasket on will almost certainly make the crankcase leak oil. It was designed to run without one and even the thinnest of gaskets will cause an oil seepage. Many people have gone down this road before you with the same results.

Where do get this infomition from Les, my 1955 has a full gasket and has no leaks but will burn a bit.

From the person who rebuilt my engine and does them for a living... you know who that is without me mentioning names

seems as though many have also gone down this line with plenty of success though so we will see .

[leswaller]

The perceived wisdom of others behind my statement is as follows.
The engine was designed not to have a gasket in the centre as it is not necessary to seal the crankcases at this point. Therefore there is insufficient clearance to use a gasket. Doing so will prevent the perimeter bolts being tightened down far enough to seal the perimeter gasket, and so the engine will seep oil round the edges.
"You pays your money and you makes your choice"

[ducati2242]

The perceived wisdom of others behind my statement is as follows.
The engine was designed not to have a gasket in the centre as it is not necessary to seal the crankcases at this point. Therefore there is insufficient clearance to use a gasket. Doing so will prevent the perimeter bolts being tightened down far enough to seal the perimeter gasket, and so the engine will seep oil round the edges.
"You pays your money and you makes your choice"

Sorry les but that makes no sense at all . Bolts when tightened around the perimeter will tighten the cases against the gasket it would be impossible for anything but . How do you think the gearbox keeps the oil in there . The bolts are as tight with a gasket in as they would be without . I build all my own engines and have been fitting for 40 years so its not a problem for me to take an engine out and rebuild it, especially something as simple as a matchless twin, doubt it will leak but no big deal to re do if it does.

[ajscomboman]

The perceived wisdom of others behind my statement is as follows.
The engine was designed not to have a gasket in the centre as it is not necessary to seal the crankcases at this point. Therefore there is insufficient clearance to use a gasket. Doing so will prevent the perimeter bolts being tightened down far enough to seal the perimeter gasket, and so the engine will seep oil round the edges.
"You pays your money and you makes your choice"

Sorry les but that makes no sense at all . Bolts when tightened around the perimeter will tighten the cases against the gasket it would be impossible for anything but . How do you think the gearbox keeps the oil in there . The bolts are as tight with a gasket in as they would be without . I build all my own engines and have been fitting for 40 years so its not a problem for me to take an engine out and rebuild it, especially something as simple as a matchless twin, doubt it will leak but no big deal to re do if it does.

I'd have to agree with Guy, especially as most of the bits that hold the cases together are actually studs and nuts, only 3 throat bolts. With all those clamping around the perimeter the gasket has to be compressed by the cases taking up any imperfections and leading to an oil tight joint.

[G15 Roy]

So are you saying that the three bolts are that short they will not take the extra 2 thou

[ajscomboman]

So are you saying that the three bolts are that short they will not take the extra 2 thou

Who are you talking to, me or Les?

[G15 Roy]

Les

[ducati2242]

So are you saying that the three bolts are that short they will not take the extra 2 thou

Thing is it is the other way round if you push the casings apart then the three throated bolts would in effect go in further as the head would be further back . Albeit by only the thickness of the gasket . But if they were bottoming out or running out of thread , which they don't , the extra width would only help matters .

Its 30 thou or .8 of a mm .

Thanks for everyones support and advice .

[Groily]

The late Alan 'Biscuit' Jacobs was the go-to ace contributor on twins for me when I started using the forum a few years back now. Everything he wrote was well-founded and based on long experience.
He was a believer in the use of a gasket because he thought the small paper job round the filter tunnel was inelegant and could contribute to misalignment (however small). He recommended a material called Hallite.
I have followed his advice since, but using Flexoid gasket paper. It's worked fine for me, at least. He also had valuable thoughts on cylinder base gaskets, and on almost any other leak-prone part of a twin!

This was his actual post on the crankcase joint:
Mon Aug 18, 2008 8:36 am

Forum: Help
Topic: Twin oil leak
Replies: 12
Views: 845

Twin oil leak
An all over crankcase gasket between the halves, works every time. 1/32" Hallite or similar. Always ... ring works also, but the gasket can solve other problems, with the ridicuously narrow joint faces, particularly in the area of the oil gallery between the cylinders.

[leswaller]

So are you saying that the three bolts are that short they will not take the extra 2 thou

No, the person who gave me the information is saying that because the centre joint with a gasket is fractionally thicker than it would be otherwise, then the perimeter bolts/nuts/studs can only close the perimeter joint so far (not far enough) without distorting the crankcase, hence the likely hood of oil seepage round the perimeter.

And just a thought of my own, if an 'allover' gasket is better then why wasn't it specified originally?

Dont shoot the messenger!