Leak Down Test (Don't Laugh!!)

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When in doubt, tear it apart. If "a mate who used it a bit but let the oil run low & seized a piston", there may be other gremlins in there. I am really using my imagination here but excess oiling from the RH rod journal due to low oil damage might be a culprit. Still, a good oil control ring should handle most of that.

One other thing to have a look at is whether the engine is wet sumping and not scavenging oil. After you run it for a bit, shut it down and pull the drain plug on the engine botton and there should not be much oil at all there, maybe 1/4 cup or less. Someone here might have the official specs on that. This is an easy check. Wet sumping can be a result of numerous things. Maybe the seizure damaged the scavenge pump or partially plugged an oil gallery on the return side. The excess oil in a wet sump condition could overwhelm the oil control rings - but why only one?

Again, just my opinion here but an oil ring sticking is not something I have seen other than in seizures where aluminum has smeared across and locked the rings in place.

If the head is off or you are committed to taking the head off you are really not that far away from pulling the engine apart and checking rod bearings and journals for peace of mind.
 
On the other hand, in true Norton enthusiast spirit, maybe the bike needs a good hard thrashing to get it real hot and loosened up. Find a route where it is up hill steep all the way around and get as much WOT time and see what happens - but keep your fingers on the clutch lever just in case.
 
And would you say you have had it run completely smoke free for an interval at some point during your ownership?
 
On the other hand, in true Norton enthusiast spirit, maybe the bike needs a good hard thrashing to get it real hot and loosened up. Find a route where it is up hill steep all the way around and get as much WOT time and see what happens - but keep your fingers on the clutch lever just in case.

I understand what you are saying in terms of checking the engine. It took me 2 years of looking to find this Norton. I wanted something with history & I wanted knowledge of the builder. I contacted at least 4 members of the NOC independently & they all gave the builder high recommendations. I talked with him on the phone on a good number of occasions quizzing him on the knowledge I'd gained from this forum & every possible mod you would want to do to a Norton had been done, he was extremly knowledgeable of all things Norton and could feel the pride he gained from the builds he had done.

I also quizzed him at the time about the seizure, he had stripped the engine, cases apart, checked the conrods, journals etc. The rods have to be drilled because this 920 conversion uses a larger gudgeon pin. He was conscious of cleaning everything out of the engine just in case a loose 'bit' was floating around.

This chap did this for enjoyment, he did not do this for the money so he didn't want hassle in his retirement and only did work for people he knew or were recommended from friends.

With my years working on this bike I've come to appreciate all the details he put into his builds, you sort of get to know somebody when you work on a bike they built & I've never come across anything on this bike that I felt he made any shortcuts on or a feeling of 'that will do'.

My plan coming into the summer is to bring it for a really good spin, everything so far has been relatively shorts blast and bench running. I will of course keep my hand hovering over the clutch lever!!!!
 
I'm wondering if the rings on that right side have never seated properly.
Some hard running can cure that ( sometimes)

Glen
 
And would you say you have had it run completely smoke free for an interval at some point during your ownership?

Yes, the first thing I did after getting the Norton back to Ireland was to go over to Wales & did a 1500 miles pottering around, smoke free. The rest of the miles have mainly been done in Ireland, during the summer, sometimes up to 1K miles. It's a small country so doing a few 2-300 mile trips during the summer lets you see lots of it!!!

I did have some issues with black smoke a few years back but that was a carb issue, once I freshened up the carbs everything was fine after that.
 
I'm wondering if the rings on that right side have never seated properly.
Some hard running can cure that ( sometimes)

Glen
That's the plan Glen :) I might get a chance before the summer to take 'him' out & bring it up to the legal speed limit ;-)
 
Ahh, I guess I didn't put your name and handle together.

Look for possible leakage between the pushrod tubes and the bore. This is especially a problem with the 920. I usually ended up installing o-rings in the top of the barrel to prevent it. This usually gets worse as the head gets up to operating temp.

And yes, an oil ring could be the problem.

If you run the bike without the overhead oil line with fresh tight guides you may end up seizing a valve. I have done it but I don't like the idea. Jim



Jim, thanks for the reply. I, in fact, already sent the head back to you :) (I can only imagine the amount of heads you work on in a year!!) When I originally got the head back from you I installed it & did some road testing, re-torqueing etc. etc. I had smoke coming from the RHS so decided to pull the head & send it back to you just to be sure the head was not the problem (the bike had not been smoking like this prior to the head rebuild). You did the dye test and it was a OK, hence my comment that I'm 101% sure the head is OK.

This is why I'm leaning more towards an oil ring being stuck as all my compression & leak down tests seem fine?

What do you think about removing the oil line to the head just to see if the smoke stops, to point to or exclude the head?

Thinking of running the bike on the bench until I see smoke (time how long this takes as per Torontonian suggestion) then block the oil line & run it for the same amount of time & see if the smoke stops.
 
Good to hear the bottom end is in good shape click.

+What comnoz says about the head gasket around the pushrod tunnels since you are running big bores. If it is not an obvious head gasket leak then pull the barrels to set your mind at ease about the oil control ring and all rings for that matter.

Any chance the second ring (scraper) being installed upside down on the RH side would be the culprit? If you pull the barrel, I would go for a new set of rings since you already have 12,000 miles on the bike. Sounds like you have a keeper there.
 
Good to hear the bottom end is in good shape click.

+What comnoz says about the head gasket around the pushrod tunnels since you are running big bores. If it is not an obvious head gasket leak then pull the barrels to set your mind at ease about the oil control ring and all rings for that matter.

Any chance the second ring (scraper) being installed upside down on the RH side would be the culprit? If you pull the barrel, I would go for a new set of rings since you already have 12,000 miles on the bike. Sounds like you have a keeper there.

Really appreciate all the advice you have colectively given me.

My plan is . . . . . . . .

1. Run the bike as is, get it nice & hot & put some miles on it as if I was running it in again. If the smoking gets worse or stays the same after 2-300miles I'll pull the head again & see if I can see any leaks around the pushrod tunnels. If I don't see any signs of leaks I'll pull the barrels & check the rings.
I'll be back at that stage looking for more advice!!!

I'm not going to do the test blocking the oil line to the head as per Jim's advice due to the valves & guides being so new, I don't want to mess up Jim's work!!
 
No wear tear risk to reving up w/o head pressure as thats what happens on every start. Oil is a non issue until spring heat becomes a issue. Main thing is starving the cam lobes of drain down, so I'd rev up to cam break in 2000ish long enough to test. If already run in a good bit, then all the new surfaces are better burnished and the ZDDP will do its job long enough to check off another possibility. Physics, tribology and Norton type heads facts not hobot hearsay, nor Jim's. No one else/s Commando fogging its public image so get back to work.
 
I would take it for a hard ride. Since you already have the head off it is not that much extra trouble to take the cylinder off and look at the pistons but you seem to be good at getting the head on and off so if you just put it on and take the bike out for a good ride I think the ring will free up. Then after retorquing the head you should really get down on it with some hard acceleration at full engine temp. I'm sure you are running good oil. I'm using Amsoil in mine and the internals were supper clean and nice when I changed the timing cover.
 
Understand the head oil feed trepidation. Since earlier concern , Jim has stated now that he has not had an intake seal "pop" off to date. So is it an RH4 or RH 10 head ? A leaking head gasket ?
 
You could have popped loose a wristpin circlip and it's scored the cylinder wall low enough on the cylinder wall for oil to be leaking by the scratch at the control rings but out of sight when you look into the cylinder. I had that happen to me 25 years ago.

In a certain way, your issue is a no brainer, Pull the cylinders and have a look! It's really not that big of a deal. I had a lifter delaminate on me last year while my bike idled in the driveway. It started making a clack,clack,clack noise. I pulled it apart in a few hours and found the problem. No big deal. I used the down time to buy new barrel studs, and nuts. Then I cleaned and painted the barrels gloss black. BTW, Jim Comstock matched up my existing lifters to one of his barrels, then fitted a pair of good lifters to that same barrel, so he could supply me with lifters that would fit my barrels... Thanks again Jim!

But anyway click, Don't guess, pull the barrels and take a look now while it's winter... so you can ride in the summer.
 
I would take it for a hard ride. Since you already have the head off it is not that much extra trouble to take the cylinder off and look at the pistons but you seem to be good at getting the head on and off so if you just put it on and take the bike out for a good ride I think the ring will free up. Then after retorquing the head you should really get down on it with some hard acceleration at full engine temp. I'm sure you are running good oil. I'm using Amsoil in mine and the internals were supper clean and nice when I changed the timing cover.
Head is back on, did this over Xmas and did a few heat cycles on the bench, re-torqued etc. So the bike is ready to go. I’m using Silkolene 40wt a really good quality oil over this side of the world + I change it far more regularly than I should!
 
Understand the head oil feed trepidation. Since earlier concern , Jim has stated now that he has not had an intake seal "pop" off to date. So is it an RH4 or RH 10 head ? A leaking head gasket ?
RH4 head but as stated checked twice by Jim for any issues

When I did the leak down test I was listening for air leaks around the head. I could not hear any sounds, hissing etc from any leak points
 
You could have popped loose a wristpin circlip and it's scored the cylinder wall low enough on the cylinder wall for oil to be leaking by the scratch at the control rings but out of sight when you look into the cylinder. I had that happen to me 25 years ago.

In a certain way, your issue is a no brainer, Pull the cylinders and have a look! It's really not that big of a deal. I had a lifter delaminate on me last year while my bike idled in the driveway. It started making a clack,clack,clack noise. I pulled it apart in a few hours and found the problem. No big deal. I used the down time to buy new barrel studs, and nuts. Then I cleaned and painted the barrels gloss black. BTW, Jim Comstock matched up my existing lifters to one of his barrels, then fitted a pair of good lifters to that same barrel, so he could supply me with lifters that would fit my barrels... Thanks again Jim!

But anyway click, Don't guess, pull the barrels and take a look now while it's winter... so you can ride in the summer.

Good advice, many thanks.

My analytical side says pull the barrels, my biker side says just ride the bike & see what happens!!

When I got the head back from Jim for the 1st time, after 4-5 heat cycles & re-torquing I took it for a 3-4 mile spin on a long private road and got up to 90mph, pulled like a train, when I pulled in ticked over like a clock, no strange noises etc BUT lots of smoke when revving from tickover. This is the reason why I sent the head back to JIm just to be sure there was no issues

Maybe I didn’t give it enough time!

I’ll reflect on all comments made
 
Surely you can check the easy things first - just remove carbs and manifolds and look in the inlets and see if you can see oil dripping off the guides, you will have now eliminated some areas.
 
Surely you can check the easy things first - just remove carbs and manifolds and look in the inlets and see if you can see oil dripping off the guides, you will have now eliminated some areas.

Hi, did this the first time I put the head on, removed carbs & downpipes & checked the guides but no oil. I'm probably confusing everybody at this stage :)

OK.

1. I got the head work done by Jim C., fitted the head, did 4-5 heat cycles, re-torqued etc. Took the bike for a few spins, some hitting 90mph. Bike ran great but lots of smoke on tickover blipping throttle.

2. Contacted Jim & he agreed to look at the head again just in case. He did the dye test to see if there was any cracks but nothing showed up. Jim's theory was either a gasket leak into the combustion chamber or a dodgy oil ring. I must hold my hands up & say I had not annealed the copper head gasket when I installed the head :-(

3. I got the head back from Jim C. for the 2nd time & fitted it over Xmas using the reduced shank head bolts with extra stretch! from Jim C. and I used Jim Schmidt's trick of using ultra thin copper wire & Pliobond on the 920 copper gasket (annealed before use). I also checked the flatness of the deck on the barrels & Jim C. had skimmed the head, so I'm hopeful its not a cylinder head leak.

4. I've only done two heat cycles on the current head install on the bench. Approx 5 mins per heat cycle, re-torqueing the head bolts in-between.
I'll try another startup today & see how long it takes to see smoke & report back
 
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