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Cylinder head breathing

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Cylinder head breathing

Posted by Colin Peterson at September 14. 2018

As I've mentioned previously, elsewhere on this forum, my Commando has, unfortunately, taken up smoking. Grey-blue smoke, just from the left cylinder. I've tried replacing the oil seals on both inlet valve guides, with generous assistance from Gordon Robertson, but to no avail – I did both because it seemed sensible. Yesterday I ran the engine with the left exhaust valve cover off, so that I could see if oil was pooling there – maybe the drain there was blocked. No sign of oil pooling, so I'll have to take the head and barrels off to investigate further. But, while the valve cover was off, the smoking virtually disappeared! Of course, it came back when I put the valve cover back on.

I've seen people discussing the virtue of a breather outlet for the head alone: from this experience I'm convinced. Is that wrong? By the way I have a one-way reed valve from HNW in the existing breather hose, and yes, I have installed it the right way around! Tongue out

I've put this under 'Nortons – General' because I'd guess it applies to 'heavy twins' too, if not others …? I did do a quick search of the forum for existing threads on this subject, but didn't find anything.

Re: Cylinder head breathing

Posted by anna jeannette Dixon at September 15. 2018

Previously Colin Peterson wrote:

As I've mentioned previously, elsewhere on this forum, my Commando has, unfortunately, taken up smoking. Grey-blue smoke, just from the left cylinder. I've tried replacing the oil seals on both inlet valve guides, with generous assistance from Gordon Robertson, but to no avail – I did both because it seemed sensible. Yesterday I ran the engine with the left exhaust valve cover off, so that I could see if oil was pooling there – maybe the drain there was blocked. No sign of oil pooling, so I'll have to take the head and barrels off to investigate further. But, while the valve cover was off, the smoking virtually disappeared! Of course, it came back when I put the valve cover back on.

I've seen people discussing the virtue of a breather outlet for the head alone: from this experience I'm convinced. Is that wrong? By the way I have a one-way reed valve from HNW in the existing breather hose, and yes, I have installed it the right way around! Tongue out

I've put this under 'Nortons – General' because I'd guess it applies to 'heavy twins' too, if not others …? I did do a quick search of the forum for existing threads on this subject, but didn't find anything.

 

 

Hello well if you had clicked on to my Norton Manxman threads you may of found your answer   right for a start off  you not find any oil pooling on the exhaust side as all the excess oil goes down the push rod tunnel  to lube the cam followers  and the cam shaft   face,  the reason you get smoke out of the drive side exhaust is you have a blow back of oil mist  somewhere  and this will be in the inlet side  as there are oil drain hole at the sides of the in let valve guide this may be part blocked up by the fiber collar washer  under the valve spring cup  on that drive side  the Norton Manxman 650 had fitted as standard  a banjo breather from the top of the inlet cover  and in my norton manxman 650 parts manual there is all the parts number for this fitting  hope this information may shed some light of experience on your problem, yours   anna j

Re: Cylinder head breathing

Posted by Colin Peterson at September 15. 2018

Thanks anna – yes the exhaust valve 'drain' thing came to me last night as I was falling asleep! Pushrods etc, duh! ... Laughing Sorry, it's just been so long since I've had to go in there. The factory fittings you suggest were mentioned by someone at Access Norton years ago, I since found, and I'd be interested in confirmation as to whether they'd fit my 850 Commando – seems plausible, anyway! But Jim Comstock points out (at Access Norton) that internal air pressure comes from under the pistons, obviously, so a breather for the head could cause problems for oil returning from it to the bottom, as it would have to fight its way past air trying to exit through a breather from the head.

But someone else on that forum also believes that the factory breather from the head was only dropped as a cost-saving exercise by AMC. You'd know more about that than I ... And I can't really see how rising air would have much impact on oil passing down the pushrod tunnels, for example – maybe the possibility of blocked drainage on the inlet side, which you mention, wouldn't help. Maybe I'll investigate those factory fittings, unless you or someone might be kind enough to point me at them ...

I was supposed to be stripping the top end off yesterday, but was unavoidably distracted – you mention blow-back, I'm presently thinking a kind of 'blow-by' from the cylinder is probably to blame – knackered rings, for example, letting oil into the combustion chamber. I'll find out one day soon, fingers crossed it doesn't get too expensive. Cheers!

Re: Cylinder head breathing

Posted by jonathan_newton at September 17. 2018

Colin, not want to teach the sucking of eggs but  the difference between valve stem and ring deficiency is noramlly  apparent by when the smoke is produced.  If after overrun you get a plume it will be top end,  if you drive it hard and it smokes as you pressurise the cylinders then more likely rings.  I know a dominator that has smoked on the drive  side cylinder for the last 30 years.  Plug is clean, engine is dry, pulls like a train, left it like it is....

 Wasn't aware of the Manxman difference as Anna has highlighted, may do a little experiment .

Cheers

Jon

 

   

Re: Cylinder head breathing

Posted by Colin Peterson at September 17. 2018

Thanks Jon – no worries about egg-sucking, as anna established (above) I do need reminding of things sometimes! The smoking started off fairly thin so hard to establish whether on run or overrun – now it leaves a cloud of smoke hovering like a phantom when I pull away, so …! I say 'now', this is since the middle of the summer, consequently I'm not riding until I'm done fixing. Which is another story … Undecided I might get to start on it tomorrow, fingers crossed.

If you do a little experiment with the 'Manxman difference', do share the results! Cheers.

Colin

Re: Cylinder head breathing

Posted by philip_hannam at September 17. 2018

As usual, Anna is quite correct in regard of the advice given. However, I must add a little extra from my own knowledge and personal experience. Excess oil in the front rocker area will indeed drop through the pushrod tunnels. But, just like happens inside the timing cover, the falling pistons push a reasonable quantity of oily vapour into these tunnels.  This is a factor of the early Dominator engine design and is known as the 'bellows effect'. This was a feature of the pre-presure fed rocker cylinder heads and helped to lubricate the camshaft, followers, pushrod ends and to some extent the rockers. Remember, the early pre-1964 engines had their rockers fed by the low pressure return side to the oil tank.

When the exhaust valve guides become worn enough, the pressure inside the cylinder head will push oil through them resulting in mild exhaust smoking on both sides. If the smoking is from just one side this may be due to a single guide that has broken or become defective in another way.

Re: Cylinder head breathing

Posted by Colin Peterson at September 17. 2018

Thanks for the tip Philip, I'll be on the look-out!

Re: Cylinder head breathing

Posted by Alan Sessions at September 17. 2018

Previously philip_hannam wrote:

As usual, Anna is quite correct in regard of the advice given. However, I must add a little extra from my own knowledge and personal experience. Excess oil in the front rocker area will indeed drop through the pushrod tunnels. But, just like happens inside the timing cover, the falling pistons push a reasonable quantity of oily vapour into these tunnels.  This is a factor of the early Dominator engine design and is known as the 'bellows effect'. This was a feature of the pre-presure fed rocker cylinder heads and helped to lubricate the camshaft, followers, pushrod ends and to some extent the rockers. Remember, the early pre-1964 engines had their rockers fed by the low pressure return side to the oil tank.

When the exhaust valve guides become worn enough, the pressure inside the cylinder head will push oil through them resulting in mild exhaust smoking on both sides. If the smoking is from just one side this may be due to a single guide that has broken or become defective in another way.

Great stuff Phil - we all appreciate your knowledge

Re: Cylinder head breathing

Posted by anna jeannette Dixon at Wednesday 22:00

Previously anna jeannette Dixon wrote:

Previously Colin Peterson wrote:

As I've mentioned previously, elsewhere on this forum, my Commando has, unfortunately, taken up smoking. Grey-blue smoke, just from the left cylinder. I've tried replacing the oil seals on both inlet valve guides, with generous assistance from Gordon Robertson, but to no avail – I did both because it seemed sensible. Yesterday I ran the engine with the left exhaust valve cover off, so that I could see if oil was pooling there – maybe the drain there was blocked. No sign of oil pooling, so I'll have to take the head and barrels off to investigate further. But, while the valve cover was off, the smoking virtually disappeared! Of course, it came back when I put the valve cover back on.

I've seen people discussing the virtue of a breather outlet for the head alone: from this experience I'm convinced. Is that wrong? By the way I have a one-way reed valve from HNW in the existing breather hose, and yes, I have installed it the right way around! Tongue out

I've put this under 'Nortons – General' because I'd guess it applies to 'heavy twins' too, if not others …? I did do a quick search of the forum for existing threads on this subject, but didn't find anything.

 

 

Hello well if you had clicked on to my Norton Manxman threads you may of found your answer   right for a start off  you not find any oil pooling on the exhaust side as all the excess oil goes down the push rod tunnel  to lube the cam followers  and the cam shaft   face,  the reason you get smoke out of the drive side exhaust is you have a blow back of oil mist  somewhere  and this will be in the inlet side  as there are oil drain hole at the sides of the in let valve guide this may be part blocked up by the fiber collar washer  under the valve spring cup  on that drive side  the Norton Manxman 650 had fitted as standard  a banjo breather from the top of the inlet cover  and in my norton manxman 650 parts manual there is all the parts number for this fitting  hope this information may shed some light of experience on your problem, yours   anna j

 

Hello To add to this I can supply the part numbers for the inlet rocker cover Breather if required And AMC stopped making other parts to make motorcycle as cheap as possible after Burt Hopwood left Norton But by doing this did not stop the rot as even by then they could not fill customer demands and many tuned to buying Triumphs Motorcycles as they made about 50 to 1 to Norton;s manufacturing were as Norton would very luck to produce 180 per week ware Triumph would do these figure's with in a day yours anna j

Re: Cylinder head breathing

Posted by Colin Peterson at Thursday 12:16

Thanks anna, that would be interesting – it doesn't look like AN supply anything like it, and I don't want to give N*rvil any of my money, would you suggest any suppliers? Cheers.

Re: Cylinder head breathing

Posted by anna jeannette Dixon at Thursday 14:01

Previously Colin Peterson wrote:

Thanks anna, that would be interesting – it doesn't look like AN supply anything like it, and I don't want to give N*rvil any of my money, would you suggest any suppliers? Cheers.

 

Hello Colin  Well Norvil will not know about  the rocker box inlet fittings or have any of the parts numbers  for heavy twins has NorVils Business is mostly based on the Norton Commando,  and parts for the dominator are mear side line so they will not be bothered about things like rocker cover breathers having said this nor are the Norton owners club parts that bothered about rocker beathere parts any way for what its worth part number for breathe banjo part number 23478 and sleeve for rear cap part Number 23427 and the stud for rear cap cover part Number 23426 and top and bottom washers T2082/T1084 part numbers the domed nut is part number E3218 all these part numbers can be found in the Norton Parts Manuel 1961/2 And there is many other parts Not made by the Norton Owners Club Or any of the After market  business  Some are Not bothered  and some just will not make them where as the Norton owners club  parts department have a hard time getting parts made they cannot make every thing I suppose, so you have make small parts yourselves I used a C15 oil rock feed banjo union and machined it to fit the rocker cover and made a longer 5/16th stud and sleeve with a 1/8th holes in so it can breather up to the banjo you have then a 1/4 pipe fitting witch I Tee off to the rear chain drip oil feed that fit on top of the rear chain guard hope this may help anyone else out, Ps anyone would like me to make small parts that's unavailable I will make them in my own time witch I will not charge any member for my time I will charge you for any materials used at cost to me to make the siad parts and you get my bill and fitting instructions  I cannot say fairer then this,and Note I am Not a Business  I only do small part to help out members only,                 yours anna j dixon

Re: Cylinder head breathing

Posted by Colin Peterson at Thursday 18:06

That's a very generous offer, anna – I do have a complete, REME-refurbished WD B40 GB engine that has the rocker oil fittings attached, which I'd assume are the same as for the C15, but I wouldn't want to start taking bits off it … So I have none of the parts, nor do I have so much as a shed, let alone a workshop!

Jonathan Newton indicated above that he might experiment with this idea. And I don't mind admitting that things are a bit tight for me at the moment. Depending on what Jon finds (or doesn't find), I might take you up on your offer after New Year, when I hope things'll be easier for me – if that's ok with you! Laughing

Re: Cylinder head breathing

Posted by philip_hannam at Thursday 20:42

I don't want to bore you all too much but just like Anna, the engine in my Norton Dominator is also a Manxman 650. It was built at Bracebridge in 1961 and was part of the second batch of machines produced for export. My engine differs from the standard Manxman motor in that I fitted it with the later conrods with bleed holes plus a pressurised rocker feed. The oil pump had a 6 start worm and drive fitted to cope with the demands of the internal changes.

From day 1,  the engine smoked heavily on start-up. I put this down to a new engine bedding-in and expected the problem to sort itself out after the rings had done 400 plus miles. It did'n't. So I assumed that the rockers were getting too much oil and excess pressure from the crankcase. The obvious solution being to add a breather to the head, in the same manner of the original Manxman engine. ie a breather via the inlet rocker cover stud. This appeared to work and the smoking diminished but never went away completely until the Chrome piston rings had 2000 miles of wear.

The extra bad news being that when the engine oil got hot. Generally after around 50 miles of fast cruising. The 500ml bottle, positioned under the seat to catch anything thrown out of the breather pipe, would overfill and start decorating the rear of the bike.

If Anna's bike is all original, then it will not have conrods with bleed holes or a pressurised rocker feed. Plus it should have a 3 start oil pump worm and drive gear. Peter's Commando engine, will have similar innards to my 650 motor and hence potentially similar smoking issues.

Re: Cylinder head breathing

Posted by Colin Peterson at Thursday 22:04

Not boring at all, Philip! Only, my Commando didn't smoke, now it does … There's not much point in me speculating until I've got in there and had a look, though. In the meantime, thanks for more interesting input!

Re: Cylinder head breathing

Posted by anna jeannette Dixon at Friday 12:27

Previously philip_hannam wrote:

I don't want to bore you all too much but just like Anna, the engine in my Norton Dominator is also a Manxman 650. It was built at Bracebridge in 1961 and was part of the second batch of machines produced for export. My engine differs from the standard Manxman motor in that I fitted it with the later conrods with bleed holes plus a pressurised rocker feed. The oil pump had a 6 start worm and drive fitted to cope with the demands of the internal changes.

From day 1,  the engine smoked heavily on start-up. I put this down to a new engine bedding-in and expected the problem to sort itself out after the rings had done 400 plus miles. It did'n't. So I assumed that the rockers were getting too much oil and excess pressure from the crankcase. The obvious solution being to add a breather to the head, in the same manner of the original Manxman engine. ie a breather via the inlet rocker cover stud. This appeared to work and the smoking diminished but never went away completely until the Chrome piston rings had 2000 miles of wear.

The extra bad news being that when the engine oil got hot. Generally after around 50 miles of fast cruising. The 500ml bottle, positioned under the seat to catch anything thrown out of the breather pipe, would overfill and start decorating the rear of the bike.

If Anna's bike is all original, then it will not have conrods with bleed holes or a pressurised rocker feed. Plus it should have a 3 start oil pump worm and drive gear. Peter's Commando engine, will have similar innards to my 650 motor and hence potentially similar smoking issues.

 

Hello Phill My manxman motor has Now the later conrods with blanked off oil holes on  minus 10 Vandervell shells new regrind  and this on 3 start oil pump with rock feed from the return side oil tank union , Has I am still on 3 start you there for have to use the large end shells with No oil holes in them  So the large end shell bearing Can maintain its oil pressure  of 60 psi  when hot this may fall to 20 psi  but still be ok , Norton tested the 650 on fast runs down the then new M1  and the Testers found the oil presser to drop to next to zero but the engine did not size up or let go of its rods  even after a long hard rides and speeds over 110mph  and then tested on a rolling road for 4 hours  at various speeds  and all this was done well before the 650 was put into production  and by february 1960 the 650 then were fitted with twin flex oil rings where as my early motor has a five peace oil ring set up made by BHB as standard and I have tried both the twin flex and five peace oil rings and the Five peace oil rings are that bit better of controlling the oil as their is a expander ring under the other five thin oil rings one of the five is a wavie ring tow thin rings fit at the top and one wavie ring one plane ring at the bottom all fitted with in the grove for the oil rings the chrome top compression ring marked top next the secondary control ring is in black chilled iron with top marked on this so you know witch way up it fits if the rings are fitted incorrectly you will get an oil blow by , and most of this blown out via the timed cam Breather, the BHB pistons are short skirt type of piston But do have and re enforced boss around the Gudgeon pin area and a row of oil hole around the oil ring area the pistons are not straight from top to bottom there flared out so the narrowest point will be the top or the crown of the piston the button skirt gradually goes out ward , if you measure and piston and take reading from the crown to the bottom of the skirt you find as much as a 0.35 thou difference the job of a piston skirt is to control side to side play at speed witch the piston changes direction some 250 time per-second and hit temperatures of over 350f so your pistons and its motion parts are constantly trying to rip them selfs apart and the oil has t do a number of things cool the inturnals part in motion and lubricat as well, , so now you have a bit of insite to whats going on inside your Norton Motor Yours Anna J

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