Repair 101 - gasket help

I am about to embark on the ultimate, perhaps impossible quest of sealing all my leaks.
I got gearbox, valve cover, and of course, the ever popular primary case seepage.
Assuming proper and functional seals, is there one 'best' way to approach this?
The choices are a bit intimidating. I can get gaskets in cork, paper composite, or rubber compounds.
I can apply Vaseline (seen it recommended for cork), Permatex, or other gasket conditioners.
Or I could use the "Right Stuff' gasket maker and forget about buying custom cut.

Sooo... hoping for specific recommendations for common leak sources. I realize each application might be different.
valve covers
primary case
gearbox

(perhaps this should be in the General Classic Motorcycle forum?)

Tachometer Drive. Have it machined out to fit a seal. A fun winter project.

tomspro said:

(perhaps this should be in the General Classic Motorcycle forum?)

Click to expand...

No this is where it needs to stay. It is a technical question relating to your bike, which I assume to be a Classic Norton of some form.
I would suggest to you to do a forum search on sealants/gaskets and read the data available that member’s use.
I don't use the paper base gasket between the barrel and case halves. Loctite 518 instead.
Cheers,
Thomas
CNN

Tom,

Taking things apart first will determine the best course of action. You really need to examine the mating surfaces and
see if a previous owner damaged a mating surface by prying on it. Also you may have a poor sealing job causing more harm than good.
A good cleaning of the mating surfaces and new seals / gaskets may work wonders (I just rebuilt my transmission and didn't use a drop of gasket goo and it's oil-tight). Does the primary leak from the mail seal around the perimeter or from the rear, maybe around the main shaft or alternator wire grommet? My `71 alternator grommet had gone hard and was rattling around in the hole. I gave it a nice dollop of silicone from the inside and let it cure fully. You can check the primary case fit by removing the seal, then cleaning everything and test fit it to the case to see if you have a uniform gap around the perimeter without the rubber seal. If the gap varies then you have a distorted case or cover. Make sure sure isn't any gouged metal on the mating surfaces. If so you can dress them lightly with a file.
On my `71 I used to run a bead of silicone around the o-ring groove before fitting the o-ring. I think my case was distorted.
For the rocker covers you can flatten them on a piece of glass with some 600 grit emery paper, stock paper gaskets should work fine as there's no pressure inside the head. You can remove the rocker cover studs and apply a little sealant to the threads to prevent oil from wicking up the studs. I've not done this but it's on my list of things to try.

And finally, remember these old crocks all leak a bit. That's part of their charm.

tomspro said:

I am about to embark on the ultimate, perhaps impossible quest of sealing all my leaks.
I got gearbox, valve cover, and of course, the ever popular primary case seepage.
Assuming proper and functional seals, is there one 'best' way to approach this?
The choices are a bit intimidating. I can get gaskets in cork, paper composite, or rubber compounds.
I can apply Vaseline (seen it recommended for cork), Permatex, or other gasket conditioners.
Or I could use the "Right Stuff' gasket maker and forget about buying custom cut.

Sooo... hoping for specific recommendations for common leak sources. I realize each application might be different.
valve covers
primary case
gearbox

(perhaps this should be in the General Classic Motorcycle forum?)

Click to expand...

My primary is belt, so no oil, so no leaks. But I doubt there's much new to do there as the original rubber seal etc looks good to me?

For all general gasket faces, I still use old Wellseal. I apply it with a small modellers brush and still find it very effective. It has the added advantages of not causing problems if over applied bits get into oil ways, and being very easy to disassemble.

Base gasket for me is zero gasket, just Wellseal applied to both surfaces before fitting.

Rev counter drive oil tightness was solved by fitting electronic tacho!

Needless to say, any quest for oil tightness on a Norton should surely start with the fitting of some kind of reed valve breather? I fitted the Comstock sump plug replacement type and it seems to be a most effective device IMHO.

Mine is very oil tight, so the above solutions seem to work for me! So far at least...

The best gasket type I have used on any type engine is the Cometic type. This is a thin aluminium sheet with rubber sprayed onto each side. Totally reusable, seals perfectly every time. Don't know if they are available for Commandos however....
My MK3 does not leak any oil..... almost afraid to say that for fear that it will spring a leak. It came to me more or less that way. I have had to pull a few things apart over time and have not always had perfect sealing afterward, which meant redoing to get it oil tight.
At this moment in time it is completely oil tight, so it is possible.
Even if it sits for five months of poor riding weather and fills it's sump, there is nothing on the floor. Also, when run hard for three or four hundred miles per day, all dry. Sometimes I wonder if there is oil in there and have to check!
My 650SS on the other hand,needs to wear a Depends after the sump fills , usually in only three or four weeks of sitting. And running it as hard as I do the Commando would definitely create a few weeps.

Glen

On rocker cover gaskets, I find it is best to trim the gasket near the bottom stud, as otherwise this acts as a reservoir and the oil can work it's way up the stud and leak out beneath the nut.

mschmitz57 said:

Tom,

Taking things apart first will determine the best course of action. You really need to examine the mating surfaces and
see if a previous owner damaged a mating surface by prying on it. Also you may have a poor sealing job causing more harm than good.
A good cleaning of the mating surfaces and new seals / gaskets may work wonders (I just rebuilt my transmission and didn't use a drop of gasket goo and it's oil-tight).
.

Click to expand...

Threaded holes in alloy are susceptible to pulling a bit, this causes a raised rim around hole which at the very least prevents good pressure all around the gasket and if severe enough a split gasket at the hole. By hand, I use a 3/8 or larger twist drill to clean this up and even countersink the hole a wee bit. I use a thin smear of high temp silicone around push-rod tunnels ether side of a composite head gasket and Honda Bond on the engine cases. No other sealant and I do use a paper base gasket, but would think about eliminating it if I have to have the barrels off in the future as it seems like a lot of us have good luck without one. My engine doesn't leak but being a MK3 I do not have to contend with the big "O" ring primary case seal. The key to that is having the stud adjusted and shimmed so the single chrome nut can be tightened fully without cover distortion.

You've read about the crankcase breather, yes?

I had a few seeping type leaks on 1974 Commando after putting together..I installed Comstock breather and the engine is free of any oil leaks...I went the entire process plugging appropriate holes and drilling new oil hole...

Fast Eddie said:

Needless to say, any quest for oil tightness on a Norton should surely start with the fitting of some kind of reed valve breather? I fitted the Comstock sump plug replacement type and it seems to be a most effective device IMHO.

Mine is very oil tight, so the above solutions seem to work for me! So far at least...

Click to expand...

I have done the very same thing to solve the oil leaks caused by positive pressure within the engine crankcase. Mine isn't the sump plug but the 72 type which needed the LH Cr/case to be machined which I did myself. I couldn't be happier. I would place this reed valve in the "Things I do not regret buying" thread.
Thomas
CNN

Thanks for all the good gasket info.

As to crankcase breather, I have a one-way valve installed on the hose, but did not seem to help.
I need to get my case modified before installing the comstock valve.
Maybe this winter....