Max sustainable RPM?

Similar to Jerry, 750 with Web312A, Comstock head with O/S valves, 10.5-1 static compression, carillo rods, crank dynamically balanced to 72%, cam advanced approx 5 degrees, standard 32mm Amals. 5500 Rpm puts me at approx 80 Mph in top gear, which is far too fast for our local congested highways in the GTA anyway, I tend to find myself settled at 4500-5000 Rpm, engine is happy here with power above if need be
 
No engine is designed to run at max revs without maintenance of stripping down after x number of hours.
IMO if it's in good condition, it will happily run at the max torque revs for long life, subject to the valves/springs e.t.c. being replaced at intervals.
 
Hi,
In my opinion we all love our bikes and great tales of their deeds can be told as the night gets older and the alcohol flows. In fact the older I get, the faster I used to ride. I think the true reality is that we are dealing with a very old design that even when brand new was hardly a cutting edge engine. And how could it have been anything else? It had to be able to be produced down to a cost where the average young pommie lad could afford to buy it and work on it with a tool kit consisting of a rag tag collection of open end spanners, a hammer and a few screwdriver. Nothing exotic, nothing complex. It was designed long before the introduction of computer design And machining, it was built by a relatively small factory that couldn’t and wouldn’t invest in expensive tooling to allow more complex design.
So this rather basic motor that was fit for purpose relative to the expectations of the day was then enlarged and made more powerful over various iterations to eventually come to us a the Commando engine. Not only had it basically come to the end of its design potential but probably it was not manufactured to the highest standards as the British bike industry came under increasing financial pressure and went into decline. Brilliant engineering was available but at a cost, to point, look at the stunning cost of a Merlin engine, both in pounds and the number of man hours required, no 1960 greaser boy was going to afford anything in that league.
In post war gloomy Britain, there was not the public expectation for extreme reliability in a top shelf sporting bike that was subsequently delivered by the Japanese from the seventies onward. If you rode a Commando hard (or a Bonnie etc) it was assumed that you would spend much of your weekends up to your elbows in grease and your bike be surrounded by a fine haze of oil mist, not to mention at least a few drops of oil under the bike
So, after that long preamble, it’s my opinion that a stock 850 probably wouldn’t appreciate lengthy periods of cruising over about 5500 rpm, which when you think about it is not a big ask for an engine of that size. I’m sure a redesign in the early to mid sixties could have economically produced an engine unburstable to over 7000 but that did not occur.
We all rap our bikes out occasionally towards (or beyond) the redline but that hardly equates to sustaining that power hour in, our out. It is a credit to the designers of our bikes that they managed to stay competitive for so long without a major injection of capital and a complete redesign. one could say they were making strawberry jam out of horse-shit and succeeded surprisingly well but by the early 1970s the game was up.
Many of course Will substantially improve their engines with aftermarket parts and better assembly and reap the benefits of increased power and higher sustainable rpm but I’m not sure that was really the intent of the original question.
In my opinion, it would be a brave man who exceeded 6000 rpm on their stock bike for mile after mile, I think the bike itself would be letting the sympathetic rider know that it just wasn’t all that happy there.
just a thought
alan
 
Alan L said:
Hi,
In my opinion we all love our bikes and great tales of their deeds can be told as the night gets older and the alcohol flows. In fact the older I get, the faster I used to ride. I think the true reality is that we are dealing with a very old design that even when brand new was hardly a cutting edge engine. And how could it have been anything else? It had to be able to be produced down to a cost where the average young pommie lad could afford to buy it and work on it with a tool kit consisting of a rag tag collection of open end spanners, a hammer and a few screwdriver. Nothing exotic, nothing complex. It was designed long before the introduction of computer design And machining, it was built by a relatively small factory that couldn’t and wouldn’t invest in expensive tooling to allow more complex design.
So this rather basic motor that was fit for purpose relative to the expectations of the day was then enlarged and made more powerful over various iterations to eventually come to us a the Commando engine. Not only had it basically come to the end of its design potential but probably it was not manufactured to the highest standards as the British bike industry came under increasing financial pressure and went into decline. Brilliant engineering was available but at a cost, to point, look at the stunning cost of a Merlin engine, both in pounds and the number of man hours required, no 1960 greaser boy was going to afford anything in that league.
In post war gloomy Britain, there was not the public expectation for extreme reliability in a top shelf sporting bike that was subsequently delivered by the Japanese from the seventies onward. If you rode a Commando hard (or a Bonnie etc) it was assumed that you would spend much of your weekends up to your elbows in grease and your bike be surrounded by a fine haze of oil mist, not to mention at least a few drops of oil under the bike
So, after that long preamble, it’s my opinion that a stock 850 probably wouldn’t appreciate lengthy periods of cruising over about 5500 rpm, which when you think about it is not a big ask for an engine of that size. I’m sure a redesign in the early to mid sixties could have economically produced an engine unburstable to over 7000 but that did not occur.
We all rap our bikes out occasionally towards (or beyond) the redline but that hardly equates to sustaining that power hour in, our out. It is a credit to the designers of our bikes that they managed to stay competitive for so long without a major injection of capital and a complete redesign. one could say they were making strawberry jam out of horse-shit and succeeded surprisingly well but by the early 1970s the game was up.
Many of course Will substantially improve their engines with aftermarket parts and better assembly and reap the benefits of increased power and higher sustainable rpm but I’m not sure that was really the intent of the original question.
In my opinion, it would be a brave man who exceeded 6000 rpm on their stock bike for mile after mile, I think the bike itself would be letting the sympathetic rider know that it just wasn’t all that happy there.
just a thought
alan
Click to expand...
That sums it up quite well.
We are lucky that the old things hang together for the most part and that they work so well.
In stock form they are just lovely on a fast mountain road , no problem passing or leaving a string of traffic behind when you need to.

I suspect that the Hele/Hopwood Triples are a much sturdier design for hop up and high rpm use.
A clubmate has reconfigured his Triumph Triple a bit. It now does 200 + mph! Not kidding, he has a record at Bonneville.
Look up Tom Mellor Trident.

Glen
 
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A limiting factor is the oil temperature.
Keep a std 850 at 5000+ rpm over 100 km on a hot day, and oil will go over 120 °C.
Time to back off..
 
ludwig said:
A limiting factor is the oil temperature.
Keep a std 850 at 5000+ rpm over 100 km on a hot day, and oil will go over 120 °C.
Time to back off..
Click to expand...
Hi Ludwig,
I would have thought that 120C would be a totally acceptable temperature for a high quality oil.
I also believe that provided the correct viscosity is used that oil performance tends to improve as it gets hotter until its design temperature is exceeded and breakdown starts to occur. In other words, cooler oil is not necessarily better oil.
I don’t want to reignite the perennial argument as to which oil is best but if one is running a very high quality (synthetic?) oil, I suspect that oil temperatures shouldn’t be of major concern. If it is, then it‘S probably symptomatic of the entire engine running too hot.
One could look at the Trident and say that obviously BSA/Triumph thought oil temp an issue, hence they included a cooler but I wonder if that was not an attempt to lower the temperature of the overall motor?
just a thought
Alan
 
This is true, the Nortons run pretty hot.
The Vincent runs much cooler. The oil never gets as hot in the Vin.
I recall stopping to talk with a friend after a long run on a hot day. When I went to restart the Norton 3 or 4 minutes after shutting it off, the engine was dead for 5 kicks. Finally I had to tickle the carbs to get it to go.
I guess the intense heat of the engine eliminated the usual fuel vapors that normally let a warm engine restart on half a kick.
It was bloody hot, lots of clicking noises as it cooled a bit.

Glen
 
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Alan L said:
One could look at the Trident and say that obviously BSA/Triumph thought oil temp an issue, hence they included a cooler but I wonder if that was not an attempt to lower the temperature of the overall motor?
just a thought
Alan
Click to expand...
I think so. When you add up the oil tank, large long oil lines, an oil filter, and oil cooler the oil capacity is bigger so even if the cooler was not doing anything, the oil and therefore engine would be cooler. Given the location of the Trident oil filter, some cooling was provided where no moving air reached. IMO, the air cooled vintage British bikes were close to the edge where hot was too hot in some conditions.
 
Alan L said:
Hi Ludwig,
I would have thought that 120C would be a totally acceptable temperature for a high quality oil.
I also believe that provided the correct viscosity is used that oil performance tends to improve as it gets hotter until its design temperature is exceeded and breakdown starts to occur. In other words, cooler oil is not necessarily better oil.
I don’t want to reignite the perennial argument as to which oil is best but if one is running a very high quality (synthetic?) oil, I suspect that oil temperatures shouldn’t be of major concern. If it is, then it‘S probably symptomatic of the entire engine running too hot.
One could look at the Trident and say that obviously BSA/Triumph thought oil temp an issue, hence they included a cooler but I wonder if that was not an attempt to lower the temperature of the overall motor?
just a thought
Alan
Click to expand...
120c is about 250 f. From my reading, most oils start to break down and lose the lubricating qualities right around this temp. By 280 f it's probably all over.
So if the oil is at 120c, it would be prudent to back off.

Glen
 
I have ran a Lochart oil cooler on my 850 since 1977 all year round without a termostat as well Pennzol 50 grade for over 30 years then getting real Pennzol was getting harder to fine in my town, my suppler was importing it by the drums from the US of A, can still get it here but it's produced here and not the same.
I use Pennright oil for older motorcycle as well STP mixed with it.
The oil still gets up to temp but the good thing it cools it down a bit before going back to the oil tank, my motor runs so well, get longer life out of my oil and very long life out of my motor over 160k miles and I am only on my first rebore, the final hone to bore was done at tighter clearance and first 100 miles was clocked up on a very cold night and my motor is still tight.
When I do a oil change the oil still has it velocity and no bad smell to it, my round oil tank is only 3ltr so 2ltr oil and what's in the oil lines/cooler, when riding I can put my hand on the oil tank without burning my hand, with the work done to my motor it can handle high RPMs longer without any problems at all.
Infact my Norton runs well in traffic with stop and goes, great on the open roads and high performance up in the Ranges without cooking the oil.
 
ashman said:
I have ran a Lochart oil cooler on my 850 since 1977 all year round without a termostat as well Pennzol 50 grade for over 30 years then getting real Pennzol was getting harder to fine in my town, my suppler was importing it by the drums from the US of A, can still get it here but it's produced here and not the same.
I use Pennright oil for older motorcycle as well STP mixed with it.
The oil still gets up to temp but the good thing it cools it down a bit before going back to the oil tank, my motor runs so well, get longer life out of my oil and very long life out of my motor over 160k miles and I am only on my first rebore, the final hone to bore was done at tighter clearance and first 100 miles was clocked up on a very cold night and my motor is still tight.
When I do a oil change the oil still has it velocity and no bad smell to it, my round oil tank is only 3ltr so 2ltr oil and what's in the oil lines/cooler, when riding I can put my hand on the oil tank without burning my hand, with the work done to my motor it can handle high RPMs longer without any problems at all.
Infact my Norton runs well in traffic with stop and goes, great on the open roads and high performance up in the Ranges without cooking the oil.
Click to expand...
Hi,
I spent years of my early life worrying about the engine and oil temperature of my T160 and being mightily impressed because the oil was luke warm coming from the cooler to the tank. I think now it was rather irrelevant.
As I am almost never in stop start/traffic and probably wouldn’t choose to ride on a stinking hot day so I don’t think excessive temps are really relevant to me. I suspect most over-heating is due to poor tuning such as incorrect ignition timing
Spare a thought for my poor Yamaha TTR250 work bike on the farm. I don’t know how it stands up to the abuse. Pushing sheep up a very steep hill, constantly slipping the clutch at probably less than 1km/hr has the engine absolutely smoking with heat, far beyond anything I would ever let my Norton experience, yet apart from hardened rubber seals it seem to accept the abuse. To make matters worse, coming out of very wet times, the cooling fins are often caked in mud.
I do use the best synthetic oil changed very often on all my engines.
regards
alan
 
I remember one of the older blokes at work was talking about when he was a tank driver in ww2
Someone asked him how fast the tank would go
He said 24 mph
We said how long could you maintain that speed for?
He replied "for as you were being chased" 🤣🤣🤣🤣
 
Down here we don't have that many roads that are long enough to be able to maintain 6000 + rpm... nethertheless ..I still think any type of extra cooling/ capacity is a good thing.
 

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A Poore Era after the Q. C. rework , stated 5.600 Continuous , in advetising for the Stock 850 .

Parently he had pulled out his thumb after being passed by kraut krap on autobahns but no British stuff . ( theyed all had to stop to pick up the bits that'd fallen off . ( just Kidding ) ) .
in is Merc. at 90 plus .

All the Early DB4s blew up on a SUNDAY in Europe .
It was HOT . ( racing on autostradas etc )
IMMEDIATE remedy & post fit was a LARGER SUMP .

Wots one ere ,
Max sustainable RPM?


Max sustainable RPM?


The MORAL of this STORY , is if you havnt put a larger OIL TANK in , dont race the Hondas on the Autostrada in daytime .

The puter sois 1.2 Litre . which is TWO PINTS , which AINT ENOUGH . You want THRE Imperial Pints , plus one for air .

A one Imperial Gallon Volume . Going quick - oil can be everywhere in lots - so not a lot LEFT in the TANK , at speed .

A Alloy Tank would warm your ass better as its more conductive than steel . the Oil'd alsop run cooler . Fit'n eet shield .

Recently Figured THIS wouldve done 200 + ( six Cylinder ) IF It'd had decent fuel . perhaps. as the OFFICIAL Le Mans fuel was notoriously rotten .
www.hagerty.com

Aston Martin’s last great prototype could become the most expensive British car ever sold at auction - Hagerty Media

It hit 199 mph. It also never won a race.
www.hagerty.com www.hagerty.com

Thats 1963 , so same era DESIGN . Holding it full throttle on the Mulsane Straight , It'd need adequate oiling and cooling , & the jetting ' IN ' .

Max sustainable RPM?


So , if your NORTON's assembled to the SAME STANDARDS . . . .
 
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Australia is a big dry hot country and OS travellers just don't understand our long distance and our hot summers so cooling is very important in the top end and middle Australia from north to west, southern state aren't as bad but still get hot in summers where they get snow in the Alps.
Great Britian will fit 25 times in Australia and NZ is a broken piece that broke off Australia millions of years ago.
But the best part Aussies and Kiwis get on so well, we put sh#t on each other and the best part we are so far away from the rest of the world, some may say we are to relaxed in our ways but that's how we like it.
So to me running a oil cooler all year round is very important, a few might disagree with me but hey it works well for all my old British bikes I have owned even my 2013 Thruxton had a fitted oil cooler from the factory and my 2016 Thruxton well it's water cooled.
 
Theyre Not allowed to Top up the Oil before a predemermined number of Laps . Not the Gendarme ready to arrest anybody not complieing .

Max sustainable RPM?


Max sustainable RPM?


These would do 135 mph in 1936 . so theres obviously something wromg with your COMMANDO if it wont . makes the current era look like spastics .

Max sustainable RPM?


SO a GALLON TANK . 3/4 gallon OIL , if you USE THE THROTTLE . 750 on 23 T ' sweet spot ' was 80 . - Plus .

cooling barely adequate at 105 mph continuous . The I.o.M. they reco the CRANK flung the hot oil as fast
as it went in . SO the Guage read ' ZERO ' , And the Top End Feed was compromised .

So the Last of them got a bleedyu great hypoid pump .

Max sustainable RPM?
 
It is not the temperature in the oil tank that matters, but at the hottest point in the engine.
If the oil that is flowing from the head to the camshaft is at 150 °C, an oil cooler is not going to save it.
Putting burnt toast in the freezer won't make it edible.
There are a few things that can be done to make the cyl. head run cooler.

This is an old article from Alan Goldwater, but it is still relevant :

Another reason why a std 850 cannot be ridden fast over long distances is the exhaust.
It will inevitably crack, rattle loose, or fall off all together.
During the 80-ties, I used to visit the Bol d'Or 24h at the Paul Ricard race track, France
and ride back on Monday to my place in Belgium:
1100 km in around 10 h riding time. I always came home with cracks in the exhaust pipes, till I bolted the mufflers rigid to the engine cradle, and did away with the rose nuts.
5500 rpm "all day long" .. Really?
In my experience, a reliable max cruising speed is more like 4500 rpm.
And even then, don't think too much about all those parts rattling inside your engine, or you will automatically slow down..
 
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ludwig said:
It is not the temperature in the oil tank that matters, but at the hottest point in the engine.
If the oil that is flowing from the head to the camshaft is at 150 °C, an oil cooler is not going to save it.
Putting burnt toast in the freezer won't make it edible.
There are a few things that can be done to make the cyl. head run cooler.

This is an old article from Alan Goldwater, but it is still relevant :

Another reason why a std 850 cannot be ridden fast over long distances is the exhaust.
It will inevitably crack, rattle loose, or fall off all together.
During the 80-ties, I used to visit the Bol d'Or 24h at the Paul Ricard race track, France
and ride back on Monday to my place in Belgium:
1100 km in around 10 h riding time. I always came home with cracks in the exhaust pipes, till I bolted the mufflers rigid to the engine cradle, and did away with the rose nuts.
5500 rpm "all day long" .. Really?
In my experience, a reliable max cruising speed is more like 4500 rpm.
And even then, don't think too much about all those parts rattling inside your engine, or you will automatically slow down..
Click to expand...
Cheers for that info link.👍
 
baz said:
I remember one of the older blokes at work was talking about when he was a tank driver in ww2
Someone asked him how fast the tank would go
He said 24 mph
We said how long could you maintain that speed for?
He replied "for as you were being chased" 🤣🤣🤣🤣
Click to expand...
The opposing team probably had Tiger tanks.
 
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