Dominator 88

Hi All - New to the forum, and more importantly, new Norton owner, so forgive me if I don't speak Norton yet! I do speak Velocette though

I purchased the bike from a deceased estate - the gentleman who owned it was building a Domi-Racer replica but sadly succumbed to Cancer before he could complete it. He had spent quite a lot of time and some money on replica parts and although it is very very far from original, I felt it deserved to be completed so I put in a bid and bought it. From what I can ascertain, it has the standard Engine (prefix 122) as well as the correct frame (also 122) but the gearbox is different. Honda forks, Suzuki GT750 front brake and replica oil and fuel tank complete the setup.

I did manage to fire it up after doing some of the basics, but there was a lot I wasn't happy with, so decided to go through the basics just to make sure everything was sorted. Luckily there was a Haynes Manual with the bike so that has helped a great deal, and I'm making nice progress, but have run into a problem hence me joining the forum.

After replacing both the ignition and valve timing chains I replaced the timing cover and fired it up. My concern is what I perceive to be really high oil pressure - to a point where it doesn't just leak out the timing cover, but more so pumps out! I have the correct oil pump to timing cover rubber conical grommet, and the crankcase breather seems to be breathing well back into the replica tank, and the oil is returning well to tank, but I have never experienced this type of pressure on any of the Velo's I own, hence my concern.

So my first question of many - I'm going to replace the timing cover gasket - I believe from the manual that there needs to be a clearance of 0.01" between the timing cover and the engine case. I'm assuming that this is with a gasket in place?

Secondly - the leak is out the top right of the cover - close to where the rev-counter drive is - is this significant, or is it just coincidental that it's there.

Any comments will be really appreciated!

Hi Andy - welcome to the crazy place.
The '88 should be a great project. The oil leakage issue seems a bit strange. Are you sure you actually have exceptionally high oil pressure or just a really bad leak?
It appears strange to me as the "pressure" inside the timing cover, particularly in that area, shouldn't be high.
There are such creatures such as six-start pumps which boost pressure - but I don't think that describes your situation as they only boost pressure inside the crankshaft and galleries.
I would concentrate on the flatness of the mating gasket surfaces.
Maybe someone else may have better wisdom on your problem.
Cheers
Rob

Andymann-welcome
The NHT norton heavy twin engine as well as the rolling chassis made many changes over the years.
Now you have bought an "unknown to us" modified bike.
Even after 30 years of folks talking about a DOMI or DOMINATOR, I still don't have a clue of what a domi is...500/600/650/750/850??? though I intimately know all the engines inside and out. 1949-1975
122 is 500 OK
88 is a featherbed, but slimline ???? or wideline???. Frame marking of engine type 122 does not mean anything except, what the factory originally sent as an engine in that rolling chassis.
The actual engine # and frame # matched when original and is a big clue for us.
Now we play the 100 questions game to determine "what you have" then try to determine "What your probelm is."
Can you fill us in with what 500 you have VIN/SN on the engine? dynamo or alternator should come out of the engine #

Re; "After replacing both the ignition and valve timing chains I replaced the timing cover and fired it up. My concern is what I perceive to be really high oil pressure - to a point where it doesn't just leak out the timing cover, but more so pumps out! I have the correct oil pump to timing cover rubber conical grommet, and the crankcase breather seems to be breathing well back into the replica tank, and the oil is returning well to tank, but I have never experienced this type of pressure on any of the Velo's I own, hence my concern."
did u replace the cone rubber on the oil pump/t /cover with a new one?

re; "Secondly - the leak is out the top right of the cover - close to where the rev-counter drive is - is this significant, or is it just coincidental that it's there."
have u a dynamo drive or the later Alternator cases?

Hi Gents - thanks for the replies! Yup - it certainly is a bits and pieces bike - I tried to load some pics, but haven't quite figured out how yet - but I'm working on that. The pressure is really high in my humble opinion - this bike doesn't have a rev counter drive so in the interim I made a blanking plate - very rough. The pressure was so high that it sprayed a stream from the blanking plate right out that it hit the front of the oil tank. I then machined a proper blanking plate and the leak moved to the top right of the cover, where the alternator/dynamo would be if it had one - there is a blanking plate there too. But it fairly pumps out there where the Timing cover joins the engine. It also came out the return line to the top of the head, but I have managed to stop that leak buy annealing the copper washers and torquing up the bolts correctly. I'll get the engine and frame numbers for sure so we can identify it, as well as the gearbox - someone mentioned to me it had "the correct gearbox" but that could mean anything!

dynodave said:

Andymann-welcome
The NHT norton heavy twin engine as well as the rolling chassis made many changes over the years.
Now you have bought an "unknown to us" modified bike.
Even after 30 years of folks talking about a DOMI or DOMINATOR, I still don't have a clue of what a domi is...500/600/650/750/850??? though I intimately know all the engines inside and out. 1949-1975
122 is 500 OK
88 is a featherbed, but slimline ???? or wideline???. Frame marking of engine type 122 does not mean anything except, what the factory originally sent as an engine in that rolling chassis.
The actual engine # and frame # matched when original and is a big clue for us.
Now we play the 100 questions game to determine "what you have" then try to determine "What your probelm is."
Can you fill us in with what 500 you have VIN/SN on the engine? dynamo or alternator should come out of the engine #

Click to expand...

They stopped calling them Domi twins when they went to the 750 Atlas, more or less. (although some people will disagree with me- it's still the same engine)

Bernhard said:

Re; "After replacing both the ignition and valve timing chains I replaced the timing cover and fired it up. My concern is what I perceive to be really high oil pressure - to a point where it doesn't just leak out the timing cover, but more so pumps out! I have the correct oil pump to timing cover rubber conical grommet, and the crankcase breather seems to be breathing well back into the replica tank, and the oil is returning well to tank, but I have never experienced this type of pressure on any of the Velo's I own, hence my concern."
did u replace the cone rubber on the oil pump/t /cover with a new one?

re; "Secondly - the leak is out the top right of the cover - close to where the rev-counter drive is - is this significant, or is it just coincidental that it's there."
have u a dynamo drive or the later Alternator cases?

Click to expand...

Cone rubber is new yes - I was told this is very critical - However, I didn't measure the clearance which is where I am at now - I believe it to be 0.01"? So will measure that later tonight.

This bike has neither - the fibre gear is still in place, but the opening to where the Generator/Dynamo would have gone has been blanked off.

Bernhard said:

They stopped calling them Domi twins when they went to the 750 Atlas, more or less. (although some people will disagree with me- it's still the same engine)

Click to expand...

You pretty much confirm it is a mostly meaningless term except for street level marketing

Andymann
Oil pressure is high? you have a oil pressure gauge plumbed in? How have you determined high oil pressure?

By your comments it was obviously dynamo engine

dynodave said:

Andymann
Oil pressure is high? you have a oil pressure gauge plumbed in? How have you determined high oil pressure?

Click to expand...

Just remembered, oil pressure relief valve might, I said might, want cleaning out. ( its that big domed nut on the LH side of the timing cover)

WELL YOU GUYS CAN PLAY THE OTHER 95 QUESTION WITHOUT ME .
I'll want more information to continue. I try to diagnose rather than throw hand grenades

Your image looks like a dynamo c/case but is v. poor. The relief valve can get gunged up that it will blow commando rocker pipes off.
No pic of your timing cover does it have a blanked off rev counter on there?

Andymann said:

Cone rubber is new yes - I was told this is very critical - However, I didn't measure the clearance which is where I am at now - I believe it to be 0.01"? So will measure that later tonight.

This bike has neither - the fibre gear is still in place, but the opening to where the Generator/Dynamo would have gone has been blanked off.

Click to expand...

andyman,

welcome to the forum. that should be a sweet bike once you get it figured!

the cone rubber washer is to keep the oil pressure to the big ends up, which wouldn't cause oil to spray out of your case in a short amount of run time. i'd start checking all the ways that relieve pressure first: oil pressure relief valve, the breathers for both the engine cases as well as the oil tank, etc. next, check for things that would unduly increase the pressure in a "normally" functioning system, such as the later six start oil pump with unscrolled rocker shafts, poor aftermarket attempts at head oiling, etc.

break things down into complete oiling and breathing systems from start to finish and make sure all the orifices are clear and not plugged with sealer, silicone, grit, etc. there are strangely held opinions about oil pressure gauges on the bikes, but more info is never bad if you know what to do with it. i'd plumb one into your motor while you get this figured out.

there should not be this amount of pressure in the cases. if there is, you can bet it's getting into the combustion chamber past the rings. the leaks are the symptom, not the issue at hand.

there should also not be a very large quantity of oil in the case, maybe a quarter cup/125-ish cc. it's possible that the oil had wet sumped past the oil pump into the case, and upon start up, it highly pressurized the cases. you didn't mention how long you ran it in either case and if you had checked the oil level in the motor. given a bit of run time, a correctly functioning motor with a correctly functioning oil tank will clear the oil back into the tank.

don't sweat the semantics of nomenclature. the motors changed a bit here and there, but they all function (more or less) the same. there are pairing issues such as the six start (higher volume) pump with unscrolled rocker shafts that can cause problems such as this though, so you're probably not in deep trouble, just in for some investigation. the motors spanned quite a bit of time and ideas, so there are several possibilities for what is in there, what should be in there, and what some well-intentioned previous owner tried to put in there. getting a year of manufacture will only tell you what norton put in there, not what's actually in there. the fact that this bike was customized as an homage to a very high performance motor (for the time) there's a good chance the previous owner tried to hop things up a bit, so who knows what's in there?

as with all brit bikes, do a bit of searching to find out how to best disassemble things (usually with some amount of heat) to do a good once over before you get too excited. it's always worth a bit of patience.

pics can only be directly posted by vip members. otherwise, you'll need a second party hosting site to link to. might be worth the small amount membership money to easily post pics to save the hassle while you get this figured.

cheers!

todd

There should be 0.01 inch CRUSH on the cone washer with a gasket in place, and timing cover screws tight. If, indeed, you have a 0.01 inch CLEARANCE it would explain why you have oil spraying everywhere inside the timing case.

The amount of crush is determined by placing the timing cover over the crankshaft end, with gasket in place, and pressing the cover on, and allowing it to "stand off" from the rebound of the cone washer. Then measure the clearance (0.01") between the timing cover and gasket that results (assuming the gasket is flat against the engine case). I have never been able to do this without much uncertainty.

Check the oil pressure relief valve, as Bernhard suggested. The plunger inside should have free movement.

Slick

For what it's worth, it sounds like wet sumping to me, donkeys years ago one of my monoblock carb floats stuck and dumped fuel into the crankcase, blew fuel and oil mix from various areas especially the timing chest cover . Cleaned out the engine a treat and thankfully didn't explode.

Maybe just try something simple first. Drain all oil from crankcase. Pour it back into oil tank and start engine. If problem "solved" it was caused by wet sumping. You can check if the timing case is sealing the small conical rubber washer on the oil pump that looks like a faucet washer by looking for evidence of compression or with a tiny bit of plasticine modeling clay (make sure to clean before final assembly.) Remember there's also a seal in the timing case for the end of the crankshaft. Worth checking that's not inverted or otherwise deformed.

Hi All and good morning - OK so some brilliant replies here - and all very helpful! So for a start here are the engine, gearbox and frame numbers:

Engine is 47755 122, Gearbox G102 A2062 and Frame 122 51937.

I'm going to try and address all questions above with one reply if that's ok?

I fully agree - I think the bike is going to be quite a lot of fun once I have sorted it out - It's quite different to the Velo's I own and have worked on. I've never actually ridden a Brit twin before, only singles, so I'm looking forward to getting it on the road - should it turn out to be a nice ride, I might actually then spend some time fitting lights and using it on the road. South Africa has many problems right now for sure, but one of the advantages we have is that the Police generally leave us alone, so riding a replica race bike with open Megaphones on the road won't be an issue!

So getting back to the oil pressure questions - nope, I haven't had a gauge on - the only reason I assumed it was high was because it came out the case and sprayed all over the oil tank. It might well be within spec! I actually did think about fitting a temporary Oil pressure gauge, but I can't find anywhere in the manual telling me what it should be.

I did clean out the strainer under the domed nut, but I will recheck that the pressure relief valve is free - thanks!

From what I can see, there is only one breather - it's on the LHS of the engine below the cylinder block - you can blow down it - not easily, but it is free - and when I run the motor, you can definitely feel nice strong pulses coming out - it has a clear line fitted to the oil tank and you can actually see some oil mist inside the pipe too. I am confident that it is working - although I read that it it timed - could the previous owner have got the timing wrong?

That's the only engine breather I can see though - not sure where the second one is?

I have blown down all the breather connector pipes in the oil tank and they are all open. It's a replica glass fibre oil tank and fuel tank btw.

So in terms of wet sumping - that could be an issue - I know with the Velos we actually fit a Yamaha Marine part - it's a one-way valve which works really well - without that valve the sump fills up and pours out the primary chaincase. This bike only has a tap which might well be bypassing. I'll drain the crankcase as a matter of course.

When I first got the bike, the timing cover was off - I understand from the previous owners wife, that he came in for lunch and then went to lie down and sadly never woke up, so I have no idea what he was working on. I replaced the cover, checked a few basics, and fired the bike up - after a few minutes running, it poured oil out of two holes in the back of the crankcase, pretty much where the Magneto fits. On a 500 Velo motor, there is a mod we do where we add an extra breather roughly in this area leading from the timing chest, so I assumed he must have been planning to fit an extra engine breather. The bike then stood for around 6 months.

When I got to work on it again, I removed the timing cover to look at the holes, and saw they were tapped - they were also at right-angles with the ignition timing chain (which was very loose) - this leads me to believe he was actually working on some sort of tensioner and not an extra breather - similar to what's on the valve timing chain. Obviously, there is no tensioner required there, so I replaced the chain and plugged the holes.

When I replaced the timing cover, and ran the bike the leak had now moved to the temporary blanking plate over the rev-counter drive - again, I only ran for around 5mins or so. Manufactured a proper blanking plate with an o-ring, and the leak moved to the joint between the top RHS of the cover - right where the Dynamo would be if there was one.

So the plan was to replace the gasket which had now been on and off twice, but with the crush measurement being so important, I came here for advice.

The plan now is to measure the crush of the Cone washer, make allowances for the gasket thickness, drain the crankcase, check the pressure relief valve and re-assemble.

One last question - if the crush is too small - the manual says to shim the Cone washer - is this correct?

Holding thumbs!

oh I had better mention the oil is returning to tank - years of rebuilding Velo motors has taught me that whenever you start a motor, keep the oil tank lid off and watch for returning oil before you ride off into the distance!

My cone crush washer is shimmed.

Is there a steady stream of return oil, or is air returning too?
Is the head supply coming from the return pipe?