Timing cover gasket

Not open for further replies.
Apr 15, 2004
Country flag
I'm ready to put the timing cover back on. Was wondering what people usually do regarding gasket sealer. Is a light coating of oil on the gasket good enough or should I use something more aggressive (threebond, permatex #2, or ???)

I'd like it to be oiltight but generally don't like to use the goop unless it's really necessary...


Here it depends on the gasket used. I have had some luck with the gray asbestos gaskets with no adhesive, but for the brittle, tan ones I use 3M gasket adhesive (gorilla snot) sparingly. Make sure no adhesive will be squeezed out on the engine side.

I often assemble the timing cover dry and have not had problems with oil leaks. On several occasions I've used Gasgacinch on the timing cover to hold the gasket in place. This stuff is great and is available at most motorcycle shops.

I do not recommend eliminating the gasket on the timing cover. The gasket is necessary in order to maintain proper clearances otherwise some components may become damaged. For instance, too little clearance will create an interference fit between the cover and intermediate gear. Also reduced clearance may crush the oil pump sealing washer beyond its design limits, not a good situation.

It is the tan gasket so I'll break out the goop. Don't want to redo the job a week later to fix a leak...

timing cover


Sounds like winter maintenance is going on. I just resealed my timing cover last Sunday after lapping the oil pump and adjusting the cam chain. I noticed while doing a dry run at fitting the cover there was no interference fit to the conical oil pump seal. I tried again without the gasket and still no interference. Finially I tried a 0.020" shim behind the seal and got the seal compression I was looking for. Either the new seal is thinner than the last or my wet sumping problem may have been a poor seal in the past.

I've always used Permatex to seal the timing cover gasket and it's never leaked. Put a thin coat on the metal surfaces and both sides of the gasket, let it dry a bit then assemble.
Indeed it is winter maintenance time. I'm hoping to have the bike back together for our local NOC's New Year's Day Ride (weather and road conditions permitting). Then - more winter maintenance!

Pump seal

The Mark III seal is thinner than the other. It has a small taper then flattens out, whereas the other has kind of a dome. Is there a chance the wrong seal was installed??

I'm curious; how did you check the compression on the oil pump seal washer? It's strange that the new washer would be thinner. Did you sand on the pump body where it bolts up to the block? If so the distance between the pump and the cover would increase. And as a result of this increase, some compression of the sealing washer would be lost. However, you would have to do some serious sanding in order to lose all compression.

With the addition of the shim behind the sealing washer you have effectively isolated the sealing washer from the pump. This effectively eliminates the face seal area on the pump body. But you still have a seal surface remaining, the OD of the pump spigot. Perhaps this area is sufficient to create a positive seal under pressure? Have you heard of others using shims behind the oil pump seal washer, or are you sailing in unchartered waters?


oil pump conical seal


Shimming the seal proceedure is stated in the manual. Shims are listed in the parts manual with "as needed" for qty. When fitting the cover there must be some interference from the seal, otherwise there would be no compression. I don't believe the seal is critical to the pump body, only to the oil feed spigot. The compression should seal to the cover interface and also compress around the spigot.

Thank you for acknowledging my "no timing cover gasket" caution. And thanks for the information on the twin chain Norton engines.

At the age of 15 I had my first motorcycle all of two weeks when someone told me the knocking noise was a rod trying to escape from the lower end. (Something tells me the P.O. new about this) I was referred to a guy who was a former racer who was an engineer for the company who made the bike who would rebuild it on the side in his garage. I was full of questions, one was, what kind of sealant to use with the gaskets. His words still ring true to me today. A properly assembled engine with the proper gaskets does not need any goop. I asked my Uncle who was along time diesel mech. and he confirmed this but when on to say, that may be fine for your modern day Honda (67 CL160), but the rest of us need a little help sometime.
This has been a great post. I figured we would have as many different answers as people who respond. I have used 3m (Gorilla snot), Gasgacinch, various silicones, Permatex High Tack. The problem is what goes on must be dealt with later on disassembly. Everytime I go to use a product, I hear those words about 'Proper' assembly. I used to pass it off and say that was Honda, this is Norton or whatever.
Lately, I have taken a new approach and try to prove the factory design O.K. I dress up the cover with flat sand with 400 sand paper on a piece of steal I scrounged. I then deburr the case as necessary. Then assemble with the correct gasket, dry. I snug the screws, then torgue them incremently on an inside out crossing pattern, similar to head bolts.
So far this has worked on Norton cam cover, trans cover, Mark III primary and Harley cam cover with perfect results. The best part is disassembly is easier, I seem to have to do everything twice.
I always use a new dry gasket.

David, your post on the shims with conical seal really intrigues me. Here is what my factory manuel says Section C30 / 11 third paragraph ...Very late engines use a joint gasket between the oil pump and crankcase joint faces and where a joint washer is used at this point, under no circumstances should the conical rubber seal between the oil pump and timing cover be equiped with packing shims....
Para 13, Fit a new conical rubber oil seal part number NMT272 on the oil pump outlet stub and dispense with any shims which may been fitted between the seal and pump body at the time of dismantling. Over compression of the seal will render it unfit for further use.

It appears part of the shimming process is the paper gasket behind the oil pump, and when used with the proper seal and stub outlet, should get the proper clearances without shims.

I assume you have an older manuel as this is the newer 750 / 850 combo manuel good from 1970. It seems to me Norton has superceded the older method.

One thing I don't understand is what is the 'joint washer' they are referring to. I don't see one in the parts manuel.
In that article, "The World's Straightest Commando", the author said "there is more to this than you would think." He was referring to blueprinting the chassis but I think that phrase applies to everything about these bikes! There seems to be hidden complications to even the most basic maintenance tasks.

On other bikes I like to just coat the gasket with some motor oil when I install it. I would do that on the timing cover but if it leaks I have to pull the thing off again and that involves retiming the engine. I hate retiming the engine. So the gasket is getting gooped. I just haven't decided which particular goop to use. I'll probably just use whatever seems easiest to work with. I'm well stocked with goops now :)

Mike - maybe "joint washer" just meant the paper gasket? I think the official name of the conical seal is "feed bush sealing washer". Maybe they like to call gaskets washers.

oil pump seal

Jason, Mike,

Not good, you guys are making me doubt what I did. I'm going back into the timing cover to see what the conical seal looks like. As far as knowing if there is compression of the seal, "interference fit" means when you push the timing cover into place there should be a gap caused by the rubber seal which when pushing the cover harder or tightening the screws will cause the seal to compress. If there is no interference there is no compression, right?

The '75 and later 850 MkIII had a different seal that didn't require shims. All other Commandos both 750 and 850 used the conical seal and required checking to make sure there is compression. The amount of compression is just enough to make a seal, don't completely flatten the seal. The doubt I have is .020" is a lot of shim and I haven't needed shims in the past. Better to check again and waste the seals. Then on to the blown crankshaft seal in the primary.


I'm sorry if my discussion about clearances, gaskets and such made you feel uneasy; that certainly was not the intent.

I think that Debbie was spot on with her statement that: "There seems to be hidden complications to even the most basic maintenance tasks."

I agree with you Debbie the joint washer must be the gasket. they are using different descriptions for the same item within the same sentance.

David, I really wasn't trying to make you uncomfortable, I just had different info.
I did a little checking on my C.D. and found the twin chain motor does recommend the method you describe. It describes .010 clearance between the case and cover and to either replace the seal or shim as necessary. The seal has a different part #, I don't know if it is the same or superceded. This motor also doesn't use a paper gasket behind the pump.
In retrospect, there may nothing wrong with what you have done, but what do I know. There are guys on this forum with far more experience than I.
If you do choose to go back in, I'd be interested in what you find.

Regarding the little nuiances these bikes have, I understand they are quite simple compared to the single cammers that preceeded them.
As odd as it may sound it is all these little nuiances we get to correct to have such a fine running bike that separates us from ... I don't know what, but them.
I have a couple of modern day, push button bikes that are always ready to go, but somehow I get more enjoyment out of riding these old antiquated beasts. Not just anyone can own and ride these things, it takes more commitment.

We have a saying at the office 'Everthing, affects everything.' It probably applies to most things, but it certainly applies to these Nortons.

The other saying I like is norbsa's, 'You can't win, you can't brake even, and you can't quit.'

Ride Hard, or Stay Home
oil seal

Hi Mike,

That's ok about the uncertainty. I know if I don't go back in it's going to bother me during the riding season. Besides I used a .020" thick washer rater than the "proper" store bought shim. I picked up a new cover gasket, oil pump gasket and conical seal and shims at Raber's yesterday. One thing that came to mind this morning is in the past the timing cover gaskets I used were dark grey and much thinner than the almost white ones I've been getting lately. I measured the new gastket at .027" thickness. I suspect this is some of the reason I need the shims.

Twin chain engines? You're referring to the 20M3 models before the points were run by the cam? Mine is a '72 750 combat, one chain only.

As far as experience I've owned and wrenched on four Commandos, 350 and 500 pushrod singles, '50 Dominator and '63 Electra over the last 32 years. Even with that I'm not alway positive I've done the job correctly. It's just a hobby or maybe a disease.
oil pump conical seal


I got into the timing case this evening. Good thing, the seal was completely smashed out of shape. Seems to be difficult to feel the "interference". I'm putting it back together without any shims.
Not open for further replies.