Re: Timing side oil pressure release valve

Hi Matt,

The principle of the pressure relief valve is actually quite simple. The way it works is normally with a sprung piston whichis pushed down it's bore byoil pressureallowing theexcess oil pressure to escape through holes normally covered by the pistonwhen the engine is cold.This ends up in the timing cover thus lubricating everything inside there. Too much oil pressure may do damage and certainly in my case the factthe reliefhad siezed up probably is what caused the pump to be doing next to nothing.

Where is it? You're looking for the twolarge nuts of different sizesat therear of the timing cover. If you undo the largest that butts up against the cover itself you should find youself looking at a gauze filter in the end of this assembly. If you undo the outer nut you'll find the spring with the piston behind it which may be a pain in the arse to remove, it will be tight and if it's anything like mine you may end up destroying the gauze filter. I replaced mine as it was beyond recall and stank of old oil.

One point however that your two pictures show the drive side and not the timing side.

Jim

Previously wrote:

Hi everyone, needing some advice,

I am having trouble with my dominator 99 de-luxe. Not really too sure on how the timing side oil pressure valve works. I have bought a new oil pressure release piston to renew within the timing cover.

However I dont actually know where it goes. I had assumed that there was one already stuck in the cover and it would be a case of heating it up and putting the new one in. From the INSIDE bolt hole. However the new one seems to be way too big. I bought it from RGM. And on closer inspection it doesnt seem there is anything to pull out of the timing case.

Am I doing something stupid??

Any guidance on how this system works. Does the piston go in where the photo is showing?

I have also attached some photos of the bike. Not far off now. Shes painted and almost put back together. First project. considering I have hardly ever ridden a bike, let alone restored one she isnt looking too bad. This website has helped me with all sorts of problems.

cheers

Matt

Matthew,

According to my maintenance manual and instruction book page 12 para 6 you have the correct timing cover for your bike. I have just had a look at my spare cover of the same type as yours and can advise that with the inside nut removed you will find a spring and cup type valve.

The valve should be a nice sliding fit in the cover, if siezed in the shut position oil pressure will rise up to the capacity of the oil pump, which could be considerable and not good for your engine.

The valve will lift relieving pressure which is set by placing shims under the spring in the cup thus compressing the spring and increasing the pressure that the valves lifts at.

When the valve lifts relieved oil escapes via a drilling in the cover and the hole in the nut.

If you have compresed air to hand you may find this is the best way to get the valve out.

Good luck and hope this helps

Tony

Previously wrote:

Previously wrote:

Hi everyone, needing some advice,

I am having trouble with my dominator 99 de-luxe. Not really too sure on how the timing side oil pressure valve works. I have bought a new oil pressure release piston to renew within the timing cover.

However I dont actually know where it goes. I had assumed that there was one already stuck in the cover and it would be a case of heating it up and putting the new one in. From the INSIDE bolt hole. However the new one seems to be way too big. I bought it from RGM. And on closer inspection it doesnt seem there is anything to pull out of the timing case.

Am I doing something stupid??

Any guidance on how this system works. Does the piston go in where the photo is showing?

I have also attached some photos of the bike. Not far off now. Shes painted and almost put back together. First project. considering I have hardly ever ridden a bike, let alone restored one she isnt looking too bad. This website has helped me with all sorts of problems.

cheers

Matt Hello Rob This is the wrong one for the De-lux Model These Have a Bullet shape valve that fit from the top from inside of the cover valve goes in first then the spring the screw fitting that holds it all in place

Hi Matt,

Most timing covers I've come accross have the pressure relief valve shown in Roberts attachment, these are removable without removing the cover, however, a few have a completeley different type which are only accessable after removal of the timing cover. These seem to be fitted to engines made between 1958 & 1960 ish. It would seem Norton changed them, & then reverted back again. I've attached a diagram which will hopefully explain better.

Hope this helps, Tim

Hi Matt,

Tim Gosling is correct with his diagram, I have the same cover as you on my '57 M77. Your pic shows the spring & retaining plug, but I assume the piston is still in the hole? I dont know the exact years but my '50 model 7 has the big domed nut on the outside of the timing cover, but my '57 M77 & my '60 Nomad use the same cover & relief valve as your bike ( mostexcellentbike by the way!!!), then shortly after '60 they went back to the "older" style again clear through the Commando.

So Depending on the year of your bike, you probably do have the correct cover. As you said Norvil's site (and others) state 1958-1960 uses a different pressure relief valve. On the outside of the timing cover it looks just like a standard hex bolt, rather than the big domed cap. If you need any other info, or want me too post some pics, just let me know, as my Nomad is in pieces right now!!!

Skip Brolund

Hi Skip/Matt

I first came accross this when restoring my own 99 in the early 90's. I had great difficulty convincing most of the spares suppliers that I didn't have a 'dome' on the rear of my timing cover. Having previously had a Commando, I knew exactly what they were talking about, but also knew I had something completely different. At the time, I started to make a study of Norton twin timing covers, even taking photo's of engine numbers & dating letters of machines/engines with the 'odd' timing cover. It's interesting that Skip's 1957 model 77 has this as I havn't seen one on an 'M' stamped engine before, however, my 99, although being a 58 model, ('N' stamped)with alternator & 18d2 ditributor, was, according to NOC records, built in Sept 57, so that ties in nicely. I wouldnt want to argue with Anna, but I have photo's of De-Lux Dommie's with bothtypes ofcover, so yours may well be correct,unfortunately, I cant scan themto a small enough file size to attach. Of course, I have no idea if these are/wereoriginal.

Best regards, Tim

Previously wrote:

Hi Skip/Matt

I first came accross this when restoring my own 99 in the early 90's. I had great difficulty convincing most of the spares suppliers that I didn't have a 'dome' on the rear of my timing cover. Having previously had a Commando, I knew exactly what they were talking about, but also knew I had something completely different. At the time, I started to make a study of Norton twin timing covers, even taking photo's of engine numbers & dating letters of machines/engines with the 'odd' timing cover. It's interesting that Skip's 1957 model 77 has this as I havn't seen one on an 'M' stamped engine before, however, my 99, although being a 58 model, ('N' stamped)with alternator & 18d2 ditributor, was, according to NOC records, built in Sept 57, so that ties in nicely. I wouldnt want to argue with Anna, but I have photo's of De-Lux Dommie's with bothtypes ofcover, so yours may well be correct,unfortunately, I cant scan themto a small enough file size to attach. Of course, I have no idea if these are/wereoriginal.

Best regards, Tim

Hello Tim! Do i see rightly a man admitting I am right ! Are you reading this Skip!

Auctually Anna, I thought he disagreeed with you, as in "I wouldnt want to argue with Anna, but I have photo's of De-Lux Dommie's with bothtypes ofcover, so yours may well be correct" meaning, Matt may be correct. No difference who is correct, lets just try to help Matt out with the CORRECT info no matter who provides it.

Matt, here is a link to the ebay auction where I got the original timing cover to my '60600cc nomad , lots of photoshttp://www.ebay.com/itm/330671518267?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649#ht_4367wt_1263

here is a link to pics of the correct matching engine case (alternators model)http://www.ebay.com/itm/230731354445?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649#ht_6143wt_1165

My model 77 has a dynamo, with the same timing cover. As Tim said, its really difficult when you call a supplier that has no idea what your talking about when you are trying to order a part you know is correct, and theyhaven'theard of it. I know some folks dont care for orvil, but only Norvil & Domiracer had a clue what pressure relief valve I needed when I was looking for a replacement spring for my M77.

Skip

My 1960 99 De Luxe timing cover had the internal pressure relief valve - not the usual domed one. I am sure I still have that cover on a shelf. It is currently running a non-original cover with a domed pressure relief valve and a rev counter drive. Shock horror! Engine no 85787. One of the first slimlines, registered on 15 Dec 1959 (just right for the proposed removal of requirement to MoT test pre 1960 bikes).

Gordon.

Previously wrote:

Auctually Anna, I thought he disagreeed with you, as in "I wouldnt want to argue with Anna, but I have photo's of De-Lux Dommie's with bothtypes ofcover, so yours may well be correct" meaning, Matt may be correct. No difference who is correct, lets just try to help Matt out with the CORRECT info no matter who provides it.

Matt, here is a link to the ebay auction where I got the original timing cover to my '60600cc nomad , lots of photoshttp://www.ebay.com/itm/330671518267?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649#ht_4367wt_1263

here is a link to pics of the correct matching engine case (alternators model)http://www.ebay.com/itm/230731354445?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649#ht_6143wt_1165

My model 77 has a dynamo, with the same timing cover. As Tim said, its really difficult when you call a supplier that has no idea what your talking about when you are trying to order a part you know is correct, and theyhaven'theard of it. I know some folks dont care for orvil, but only Norvil & Domiracer had a clue what pressure relief valve I needed when I was looking for a replacement spring for my M77.

Skip

OOPS! i MEANT TO TYPE "NORVIL" NOT ORVIL!!!!

Mineis one of the last of the wideline 99s from July 1959, according to the date stamped inside the mudguards. (on the rear this will be at the front inside bottom edge and takes the form "JUL 59")and it has the inside pressure valve, as does the 1960 88 & 99. The 1956 has the external domed type. The 1962/62 88, 99, 650 Std. and De Luxe also have the internal type, according to Norton's Parts list PS214.

The problem is that Norton were very poor at updating their Parts Lists and Manual illustrations. For instance, my 1959 Parts List PS206 shows the wideline frame with the old style fork-ended swinging arm and several other detail differences, so they aren't too reliable! Norvil's price list clearly statesthe different items available for these valves e.g. parts which are not suitable for 1958-1960 and parts which are - this gives a clear indication that there are differences.Having said that, you would need to know whether your timing cover is original or not. It's quite easy to identify the one with the large chrome-domed nut on the back.

I don't think there really is a "right" or "wrong" with these as Norton were known to use whatever was left in the parts bin for some changeover periods!

Lionel

The Book of the Norton Dominator Twins by W.C. Haycroft has relevant diagrams and dates re the two main variations of the timing cover. Pages 19 & 20 in my copy.

Like thepre 750cylinder heads, this is another example of a Norton part that will fit a range of engines and will adequately perform the task asked of it. So as long as the filters are clean and the spring(s) in good condition it should not matter which is on the engine.

I had 6 different spare Dominator timing covers in my collection of spares at one time. Therewere probably more versions than this made if you look at the permatations possible.

My hoardincluded the 2 variations of pressure release valve.

3 with different rev counter drive mounting bosses.

Plus you have brass badge, round plastic badge or no badge.

Sounds like you have (or had) a shelf like mine Phil. I must tally up how many timing covers are hiding up there...

Not long ago that timing covers were being hacked about to allow timing chains tension to be set with (perhaps) greater precision. I doubt many would do that now.

Cheers

Alan

I have three timing covers:

One with cutaways for setting the chain tension

One I call the "Old" type with pressure relief valve inside the cover, this was originally fitted to my 1960 99, complete with round brass badge

And one with pressure relief valve externally mounted with tacho drive fitting for the tacho gearbox complete with boss and no badge, this is now on my engine but have yet to run it since embarking on the winter refit.

Incidently I purchased the tacho drive cover from the USA and although have lapped in the pressure relief valve and tested with compressed air, do not trust it, so I have rigged up a pressure gauge and once I have it ready for a run will be able to see what pressure not only what the pump is capable of producing but what the relief valve is set at, I will use Morris Golden Film SAE 40 while it is still a bit cold switching to SAE 50 for the long hot Grampian summer

Could be an interesting test and will share the results with the forum, but only if my spelling and grammar is not criticised !!!

Tony