Why the left?

B+Bogus said:

pressure reduces along the crank oil gallery, hence the RH piston gets more oil than the LH.

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The pressure is reduced by the frictional losses within the galleries, but these are not a lot between the 2 big ends which are close together, especially on a Norton with the large diameter central sludge trap which is less restrictive than a drilled gallery. The problem is they had the exit holes in both big ends the same size. The right hand one gets fed first and with the good flow and pressure the amount of oil that comes out is more than 50% of the oil which then reduces the amount of oil fed to the left side to under 50%. So the left side suffers from a lower flow more than the slight reduction in pressure. The fix would have been to make the hole in the right side big end smaller than the left side so as to equalise the flow out of the two big ends. They would have had to experiment to find the best performing hole sizes, today it would be modelled on a PC.

baz said:

I'm guessing that maybe most riders have their wallet in their left pocket
Perhaps we could have a poll ?
Maybe that's the reason I've seen blokes wearing man bags on the right to compensate??

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My wallet is always empty.....I own a Norton remember......and my only man bag is centralized so it can't be that.

marshg246 said:

IMHO: Oil entering on both sides. The right side has the drain, so the left side oil is deeper and hotter. Often, if a seal comes off, it is the left side for the same reason.

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Agreed, plus the fact that if the bike spends a lot of time on the side stand it pools there even more.

BTW, at my last track outing I had under plug temperature sensors fitted for the first time. Left cylinder ran reliably 10C hotter than the right!

(JSM long Carrillo rods, no oil holes)

kommando said:

The pressure is reduced by the frictional losses within the galleries, but these are not a lot between the 2 big ends which are close together, especially on a Norton with the large diameter central sludge trap which is less restrictive than a drilled gallery. The problem is they had the holes in both big ends the same size. The right hand one gets fed first and with the good flow and pressure the amount of oil that comes out is more than 50% of the oil which then reduces the amount of oil fed to the left side to under 50%. So the left side suffers from a lower flow more than the slight reduction in pressure. The fix would have been to make the hole in the right side big end smaller than the left side so as to equalise the flow out of the two big ends. They would have had to experiment to find the best performing hole sizes, today it would be modelled on a PC.

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Brain flip-flopping (he's right, he's wrong, he's right).

Pressure does not equal flow. For instance, I had low flow from my kitchen sink. The water company sent a guy. He showed me that the pressure entering the house and the pressure at my kitchen sink were identical - there was a restrictive filter between.

The sludge trap throws all oil to one side. I don't know if the oil pump keeps enough flow into the crank to keep the trap completely full at all speeds, but I assume so. *If* I remember correctly the holes in the big ends are perpendicular to the trap so the amount of oil and pressure are at least somewhat evenly distributed.

Still flip-flopping!

kommando said:

The pressure is reduced by the frictional losses within the galleries, but these are not a lot between the 2 big ends which are close together, especially on a Norton with the large diameter central sludge trap which is less restrictive than a drilled gallery. The problem is they had the exit holes in both big ends the same size. The right hand one gets fed first and with the good flow and pressure the amount of oil that comes out is more than 50% of the oil which then reduces the amount of oil fed to the left side to under 50%. So the left side suffers from a lower flow more than the slight reduction in pressure. The fix would have been to make the hole in the right side big end smaller than the left side so as to equalise the flow out of the two big ends. They would have had to experiment to find the best performing hole sizes, today it would be modelled on a PC.

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Still thinking about it - now more sure you're right because every blown Norton or Triumph engine I've seen had the drive side let loose.

The crank hole size shouldn't matter if the bearing shell has the correct clearance!?!?!?! I would think the bearing shell restricts the oil flow not the hole. Just my two 1/2 cents!

mean gene said:

The crank hole size shouldn't matter if the bearing shell has the correct clearance!?!?!?! I would think the bearing shell restricts the oil flow not the hole. Just my two 1/2 cents!

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Dang it - this is causing brain pain! Agreed for the current matching hole sizes, but if one side had bigger holes, then there would be more shell exposed to the hole and therefore more oil for the shell to pass (I think).

Another (probably doesn't match) analogy. My little air compressor will provide 2.3 CFM @ 150 PSI. My big compressor will provide 10.3 CFM at 120 PSI (won't go to 150 psi).

Gents,

Why are you discussing oil flow in the crankshaft gallery? This thread is about cylinder head temperature distribution. A few percentage deviation by weight of oil mist from each crankshaft throw won't affect that side's combustion chamber temperature measurably.
What goes on at the bottom end is of no significance to the cylinder head, apart from temparature of the incoming oil. Yes, under extremely high loads there may be more friction work at the drive side, but friction accounts for a minor percentage of heat generated only, and yet another fraction of the friction heat arrives at the head - most is either washed down by oil, by conduction to the cooler bottom end, or dissipates via cylinder cooling ribs.

Let's reduce the discussion to the main parameters,

* Heat is generated by the combustion of fuel and air
* Heat dissipates by air cooling, by oil, and by the exhaust gases
* Uneven cooling will affect heat distribution within the cylinder head
* Distribution of oil left and right, as well as location of the oil drain, will affect cooling
* Presence of the timing chest and the oil reservoir therein may affect heat conduction from the top end - there is no such reservoir at the drive side, i.e., heat may (and will probably) dissipate faster at the right side.
* Uneven A/F ratios and uneven flow numbers (CFM) to each side will generate different amounts of heat to each combustion chamber for a given engine load.

Norton cylinder heads are known to run "hot". The first steps of a partial cure is to ensure the best cooling possible, and to ensure the incoming charge is correct and equal on both sides.
Also, stop running the bike on the sidestand, and for a prolonged time while stationary. It's a bad habit which does the engine no good.

- Knut

acotrel said:

I live in Australia, and my sump plug tends to leak. It is also full of shit.

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Does your crank spins backwards a well.

mdt-son said:

Gents,

Also, stop running the bike on the sidestand. It's a bad habit which does the engine no good.

- Knut

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Is this a Commando only problem due to how the engine is oriented in the frame?

My Norton doesn't know if it is on the sidestand when idling. Sitting on the sidestand does not impede return oil flow back to the oil tank, nor does it affect oil pressure at the left exhaust rocker spindle where my oil pressure gauge plumbing is connected. It might cause some weird windage issue, but I don't think much oil builds up above my sump reservoir. Also of note is the sump reservoir is further to the left on my crank cases. It is not centered. At least I don't think it is. I better check on that.

I always warm the engine up on the sidestand after starting it and getting it to settle into a smooth idle so I can get off fully suit up and let it finish warming up. Only time I don't warm it up on the sidestand is when it is already warm, and I am already suited up. I've been doing that since 1974. If I had a center stand, I might use it instead. My bike does not support the use of a center stand. I am the center stand.

Anywho, when I replaced my intake valve stem seals both of them were equally hard. Maybe they just liked being fondled.

mdt-son said:

Gents,

Why are you discussing oil flow in the crankshaft gallery? This thread is about cylinder head temperature distribution.

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AFAIK, this thread is about why it's always the left side that the valve seal goes bad. As usual, that evolved to wondering about other left-side verses right-side issues.

Schwany said:

Is this a Commando only problem due to how the engine is oriented in the frame?

My Norton doesn't know if it is on the sidestand when idling. Sitting on the sidestand does not impede return oil flow back to the oil tank, nor does it affect oil pressure at the left exhaust rocker spindle where my oil pressure gauge plumbing is connected. It might cause some weird windage issue, but I don't think much oil builds up above my sump reservoir. Also of note is the sump reservoir is further to the left on my crank cases. It is not centered. At least I don't think it is. I better check on that.

I always warm the engine up on the sidestand after starting it and getting it to settle into a smooth idle so I can get off fully suit up and let it finish warming up. Only time I don't warm it up on the sidestand is when it is already warm, and I am already suited up. I've been doing that since 1974. If I had a center stand, I might use it instead. My bike does not support the use of a center stand. I am the center stand.

Anywho, when I replaced my intake valve stem seals both of them were equally hard. Maybe they just liked being fondled.

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Especially when the crankcase mods are done that are recommended with some sump breathers, the timing chest only gets its oil supply from the intake rocker drain on the right side. On the side stand, a lot of oil must be in the drive side intake rocker area for any to get to the timing side drain when on the side stand.

Personally, I don't let any bike run while on the side stand for more than a few seconds and I don't let bikes "warm up" much before riding off gently.

marshg246 said:

Still flip-flopping!

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Measure the oil pressure at the bottom banjo of the rocker feed pipe and then at the top and see what the difference is, its the longest run of small diameter pipe at oil pump pressure so it should show the biggest drop in pressure from frictional losses from bottom to top.

Schwany said:

Is this a Commando only problem due to how the engine is oriented in the frame?

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No, it affects the Atlas & co engines also.

Schwany said:

My Norton doesn't know if it is on the sidestand when idling.

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Oh yes, it does. Oil drain from the cylinder head will certainly be affected, and depending how long you idle, there is a risk of cooking the pooled oil. The risk is greater when the engine is hot, of course.

Schwany said:

Sitting on the sidestand does not impede return oil flow back to the oil tank, nor does it affect oil pressure at the left exhaust rocker spindle where my oil pressure gauge plumbing is connected.

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Oil pressure is very low at idling speed. This may affect lubrication of the big end shells. When oil is cold, oil delivery will also be further reduced. Please recall how pump pressure increases linearly with the revs and oil flow increases with reduced viscosity.

Schwany said:

I always warm the engine up on the sidestand after starting it and getting it to settle into a smooth idle so I can get off fully suit up and let it finish warming up.

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This is contrary to common advise by the makers. Best practice to increase engine temperature is actually to start driving, slowly increasing the load.

- Knut

I thing Greg is right! I have always thought it because you finish a run & pop the bike on the sidestand. Oil in the head pools in the left hand rocker box more because of how it drains. I've always change seals as a pair but the driveside seal is always worse.
As to smoking it's usually been that the timing side smokes more!
Then again, I used to fly down the road & change down at the lights on my Trident (T160) & wait for the cloud to sweep past me across the junction.

MikeG said:

My wallet is always empty.....I own a Norton remember......and my only man bag is centralized so it can't be that.

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Ok, but is your man-bun off to the right of your head? Could explain a lot, eh?

kommando said:

Measure the oil pressure at the bottom banjo of the rocker feed pipe and then at the top and see what the difference is, its the longest run of small diameter pipe at oil pump pressure so it should show the biggest drop in pressure from frictional losses from bottom to top.

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If the flow is very high, yes, but it isn't. John Hudson, who worked with Norton 1956-76, including a few years in the development shop, quotes research figures when fitting the then new Norton 650 engine with the 6-start pump. The figures showed that at an oil temperature of 90*C,
the oil pump delivered 25.5 gph at 6500 rpm, of which nearly 13 gph went through the crankshaft and a staggering 12 gph through the relief valve, leaving only a driple of 0.5 gph for the head. The test was conducted with plain rocker spindles. I can't vouch for the validity of these figures in the engines produced from 1966 on, but you get the idea. Even IF flow to the head would reach a peak of 5 gph, the flow is only 0.0053 litres per second, or 0.74 meters per second, assuming an hydraulic diameter of 3 mm.

The oil flow to the cylinder head is really minimal, and the prime reason why these cylinder heads tend to run hot.

- Knut

Back to the crank...DS lets go when things go wrong more often than the TS. This seems to be the case with a lot of british bikes. FWIW the Enfield Interceptor had the big end journals ground differently from the factory to try to assist the DS getting enough oil. This shows how weak the pump was, oil flow and pressure were always at the Almost Good Enough point.

marshg246 said:

Especially when the crankcase mods are done that are recommended with some sump breathers, the timing chest only gets its oil supply from the intake rocker drain on the right side. On the side stand, a lot of oil must be in the drive side intake rocker area for any to get to the timing side drain when on the side stand.

Personally, I don't let any bike run while on the side stand for more than a few seconds and I don't let bikes "warm up" much before riding off gently.

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My timing side case is modified, but not by plugging holes or whatever the current recommended modifications are. Actually, it has more holes in it on the timing side.

I don't ride off gently due to having a steep uphill driveway from my garage to the street. It's best to have the motor warmed up in my case.

I'm not worried about how I start the bike and warm it up when it is stone cold. My tune is probably a little different from a stock motor with small carburetors and a vanilla cam. It won't idle after a few seconds. Might take a minute or more depending on how cold it is and how long the intake tract has been dry. I should time it if I ever remember to do it. That way I could post the time it takes to get to a smooth idle and get a bunch of advice about not having it tuned right. lol

Edit: Here's something you guys can doom and gloom about. I have 85psi at cold start. It eventually goes down to around 45psi at idle when fully warmed up. Close to 60psi underway. I'm probably washing out my big end shells at startup. Don't care. By the way, I'm not trying to recommend anything because my Norton is a toy, and nothing more. Best to consider my posts as entertainment, not advice for how to do anything right. Most have already caught on to that, but just in case anyone new shows up thought I'd mention it.

Schwany said:

My timing side case is modified, but not by plugging holes or whatever the current recommended modifications are. Actually, it has more holes in it on the timing side.

I don't ride off gently due to having a steep uphill driveway from my garage to the street. It's best to have the motor warmed up in my case.

I'm not worried about how I start the bike and warm it up when it is stone cold. My tune is probably a little different from a stock motor with small carburetors and a vanilla cam. It won't idle after a few seconds. Might take a minute or more depending on how cold it is and how long the intake tract has been dry. I should time it if I ever remember to do it. That way I could post the time it takes to get to a smooth idle and get a bunch of advice about not having it tuned right. lol

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I wish I would remember to say "stock bike" a lot more often in my posts. I haven't raced since the early 70s and that was Motocross and Hill Climbs. I don't build/work on race bikes or heavily modified bikes, so I don't think about them. Every bike I build/own, idles as soon as started including Combats, plain 750/850 Commandos, Bonnevilles, Tridents, etc.