Leak Down Test (Don't Laugh!!)

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That's bad luck for sure! On the subject of the composite cylinder head gasket I don't think I'd be happy to have 2mm hanging in the combustion chamber!
I suspect Mr Emery didn't have any 920 copper gaskets in stock so just recommended an 850 one but then again I am a cynical old git
 
rvich said:
OK, admittedly I might have missed this bit. But moving up to Part 2, you got the head back from Jim, put it on and the bike smoked the first time you started it after a few minutes?

Let's propose this. The oil didn't get hot enough to burn in part 1 until the engine warmed and was pumped into the muffler. Now the head and engine are fine but your muffler is still full of oil that smokes when it warms up! Take off the muffler, run the bike, if it smokes start tearing it down!

It's why we own wrenches. Russ
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I was thinking the same thing but someone got there before me. If you have oil in the pipes/muffers you will be getting a false reading (unless the engine keeps on churning oil into these) the only way to get round this using the pipes you have now is to remove each side of the exhaust and clean them out internally –one way is to push a potatoes –yes that vegetable _ up one end of the down pipe and either flush out with something liquid, petrol, degreaser or other and make sure you absolutely remove every last trace of the oil-a messy job that requires surgical gloves , good luck on that.
 
click said:
Funny how things work out. I had a two hour window today, got home, prepped the bike, bit more oil than usual, checked fuel, checked tyre pressures, retightened exhause nuts, cold weather gear on, wheel bike out . . . . . . . . won't start :rolleyes:

Checked plugs, no spark:confused: It's been starting on the button on the bench no problems.

I take this as a sign from the Norton gods!, just strip the engine & get on with it!!!

I'll hopefully get a start today & take the head off but first I want to trace this electrical issue, always something:(
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take the undersize gasket to a local engineering machine shop and ask them to cut to the correct bore size.
 
Bernhard said:
take the undersize gasket to a local engineering machine shop and ask them to cut to the correct bore size.
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It's a composite gasket not solid copper I think it would fall apart
 
Again some confusion:

1. I DO NOT have a composite gasket fitted at the moment
2. 6 YEARS AGO, when I removed the head it had a composite gasket fitted
3. Norvil have stated that an 850 composite gasket WILL fit their 920 conversion?

I'll get a composite gasket from Andover Norton & see how it sits on the barrels and report back

At the moment I'm tracing my electrical problem before I take the head off etc. Just about to check voltage going to Pazon 'black box' and I'll check the earths, bypass the kill & ignition switch, etc. etc. just to see what's going on!!!
 
Bernhard said:
I was thinking the same thing but someone got there before me. If you have oil in the pipes/muffers you will be getting a false reading (unless the engine keeps on churning oil into these) the only way to get round this using the pipes you have now is to remove each side of the exhaust and clean them out internally –one way is to push a potatoes –yes that vegetable _ up one end of the down pipe and either flush out with something liquid, petrol, degreaser or other and make sure you absolutely remove every last trace of the oil-a messy job that requires surgical gloves , good luck on that.
Click to expand...

We have plenty of spuds (potatoes) in Ireland ;)

I've done this before on another bike and yes it is a messy process. When I get the engine stripped I'll more than likely have to send the barrels off to get them sorted so diring this time I'll clean out the exhaust, can't wait:rolleyes:
 
baz said:
That's bad luck for sure! On the subject of the composite cylinder head gasket I don't think I'd be happy to have 2mm hanging in the combustion chamber!
I suspect Mr Emery didn't have any 920 copper gaskets in stock so just recommended an 850 one but then again I am a cynical old git
Click to expand...

I've asked Norvil for confirmation regarding the bore size, standard 850 77mm & 920 81mm and if the 850 composite gasket would not overlap the bore? I'll wait & see what the reply says & report back.
 
LOL! a nasty smoking mystery turmoil leading to possible fuel mixture investigations now turned into an electrical priority. Ugh. On each new show stopping discovery, I call it "Blank Brit Iron Staring State". Causing new issues and discovering others while investigating something else spoils my mood to be a mechanic. Best wishes stealing more life time to fetter to ride again.
 
hobot said:
LOL! a nasty smoking mystery turmoil leading to possible fuel mixture investigations now turned into an electrical priority. Ugh. On each new show stopping discovery, I call it "Blank Brit Iron Staring State". Causing new issues and discovering others while investigating something else spoils my mood to be a mechanic. Best wishes stealing more life time to fetter to ride again.
Click to expand...

It's the 'pain' sorry 'fun' you must endure owning 'classic' brit bikes :)

I've narrowed the electrical problem to the usual suspects, ignition switch or more than likely the cut off switch. I bypassed both directly connecting the negative battery terminal to the feed on the Pazon black box & I have strong spark.

I'm happy now to start stipping the engine:rolleyes:
 
Haahhahaaahhaaa, yep you sure narrowed it down alright > to any/every electrical possiblitly ya ca list but still likely missing the solution not on the list! I'm never happy stripping down mechanical stuff just to recover them back to normal, only to upgrade, so take encouragement from your attitude. Ugh almost all the time I spend typing here is putting off something else more important useful, like now - chow.
 
hobot said:
Haahhahaaahhaaa, yep you sure narrowed it down alright > to any/every electrical possiblitly ya ca list but still likely missing the solution not on the list! I'm never happy stripping down mechanical stuff just to recover them back to normal, only to upgrade, so take encouragement from your attitude. Ugh almost all the time I spend typing here is putting off something else more important useful, like now - chow.
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Small update:

Bike is back on the bench.
Removed tank, exhaust, carbs, head steady, coils.
Won't get a chance to work on the bike again till Sunday when I hope to remove the head & maybe the barrels.
 
Hi click,
As mentioned on the previous page by TinTin, I would definitely be giving the oil drain passage some serious attention. Maybe you can devise a way to pressure test it when the head is off. Porosity or a crack between it and the inlet port would possibly explain the 3-4 minute delay before the smoking starts.

A general question for everyone - and I may be way off here, but if it’s the rings, wouldn’t it smoke immediately?

A lot of jap bikes have a hollow dowel between the head and barrel on oil passages which reduces the risk of a head gasket leak. Has anyone ever done that on a Norton I wonder?

While you are going to have it stripped anyway, maybe it’s worth considering the new “waisted” head and cylinder bolts now available. Apparently they are very good at stopping head gasket leaks.

Watching with great interest, ( as are many others it seems):)

Cheers and good luck,

cliffa.
 
roiu
cliffa said:
A lot of jap bikes have a hollow dowel between the head and barrel on oil passages which reduces the risk of a head gasket leak. Has anyone ever done that on a Norton I wonder?
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Not directly relevant but on Norton singles the done thing is to machine a recess around the top of the drain oilway in the barrel and put an O-Ring in the recess.
 
ntst8 said:
roiu

Not directly relevant but on Norton singles the done thing is to machine a recess around the top of the drain oilway in the barrel and put an O-Ring in the recess.
Click to expand...

Very similarly on Velocettes, the done thing is to slightly countersink both sides then place an appropriate O-ring in the subsequent space, but it’s not as close to the combustion chamber as the Commando ( especially an over-bored one).
 
hobot knows, rings smoke immediately more so on blips, head source smoke is delayed and more so on let offs sucking on guides while intake valve open. Wet sump while ruining for oiling bores/rings takes many minutes to accumulate then has ring sealing smoking symptoms of more so on throttle less on let off and maybe not any on low steady throttle. Internal gasket leaks vary but usually more after a few minutes for most unequal Alu head iron barrel expansions and oil enough & thin enough to weep into chambers then, seen more so on throttle combustion increase flapping the gap more. Oil in mufflers generally don't smoke much just slight whiffs so mostly smells of oil unless reving up enough long enouhg to send jets of exhaust that far down headers which requires WOT deep into cam best rpm power zone. Only thing that does not match a bad gasket seal is no external evidence which would imply a good crank case ventilation keeping pressure low enough to aim oil into tunnels and intake strokes.

Correction to hobot error on piston coke, the dark crown area is shielded by the valve from direct blast so its the inside area of hemi head chamber that should be the cleanest with more carbon near exhaust valve area. Quit putting off wrenching risks and strains - like me texting to avoid more tasks I might not be able to find anything wrong to fix, so likely get to do it again till fixed, some how.
 
cliffa said:
Hi click,
As mentioned on the previous page by TinTin, I would definitely be giving the oil drain passage some serious attention. Maybe you can devise a way to pressure test it when the head is off. Porosity or a crack between it and the inlet port would possibly explain the 3-4 minute delay before the smoking starts.

A general question for everyone - and I may be way off here, but if it’s the rings, wouldn’t it smoke immediately?

A lot of jap bikes have a hollow dowel between the head and barrel on oil passages which reduces the risk of a head gasket leak. Has anyone ever done that on a Norton I wonder?

While you are going to have it stripped anyway, maybe it’s worth considering the new “waisted” head and cylinder bolts now available. Apparently they are very good at stopping head gasket leaks.

Watching with great interest, ( as are many others it seems):)

Cheers and good luck,

cliffa.
Click to expand...

Many thanks for the reply.

I’ll definitely check the oil drain hole

From the little I know & what others have said, it’s possible to have an oil ring only not working & it can take some minutes before oil builds up on the bore before you see smoke as the oil ring is not scraping it away.

Already have the waisted bolts
 
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cliffa said:
Very similarly on Velocettes, the done thing is to slightly countersink both sides then place an appropriate O-ring in the subsequent space, but it’s not as close to the combustion chamber as the Commando ( especially an over-bored one).
Click to expand...
Hi lads,

I think Jim C. has mentioned something similar using copper rings to help with sealing around the pushrod tunnels and oil drain hole.
 
hobot said:
hobot knows, rings smoke immediately more so on blips, head source smoke is delayed and more so on let offs sucking on guides while intake valve open. Wet sump while ruining for oiling bores/rings takes many minutes to accumulate then has ring sealing smoking symptoms of more so on throttle less on let off and maybe not any on low steady throttle. Internal gasket leaks vary but usually more after a few minutes for most unequal Alu head iron barrel expansions and oil enough & thin enough to weep into chambers then, seen more so on throttle combustion increase flapping the gap more. Oil in mufflers generally don't smoke much just slight whiffs so mostly smells of oil unless reving up enough long enouhg to send jets of exhaust that far down headers which requires WOT deep into cam best rpm power zone. Only thing that does not match a bad gasket seal is no external evidence which would imply a good crank case ventilation keeping pressure low enough to aim oil into tunnels and intake strokes.

Correction to hobot error on piston coke, the dark crown area is shielded by the valve from direct blast so its the inside area of hemi head chamber that should be the cleanest with more carbon near exhaust valve area. Quit putting off wrenching risks and strains - like me texting to avoid more tasks I might not be able to find anything wrong to fix, so likely get to do it again till fixed, some how.
Click to expand...

Thanks for all the info & insights

I’m in the process of tearing down the motor.

Won’t get a chance to start wrenching again till late on Sunday.

I’m having a problem getting the head off!! That Pliobond really sticks the head down. Just need some patience and a bigger hammer
 
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