Available engine performance

grandpaul said:

The spirit of hobot is strong in this one...

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Wacky Backy is universal it seems

Instead of searching for more hp , I kept the engine of my Commando standard ( sort of..) and focused on reliability, weight reduction, brakes, suspension, etc..
For more than ten years now (not last year) we have a 3-day meeting somewhere in the Alps, friends from diff. parts of Europe who share the same love for the mountains.
I am the only one with an 'old' bike.
At the start of our first ride out, They asked me if I was sure to join them, because they had no intention to slow down or wait for me to catch up.

They don’t ask that anymore..



L-R : Triumph, Norton, Ducati, Kawasaki, Honda, Triumph, Kawasaki.

A stock motor is an advantage on that type of road. Big cam, big ports and big carbs all become quite useless.
Lightweight is everything, especially as we age.
Throwing a 500 lb bike back and forth is OK for about 20 minutes. After that the fun turns into work!

Glen

The theory is that more power makes you faster. But that only applies when you are going in a straight line. In corners, torque and handling matter more. What is more important is getting the power onto the ground in corners. The faster you are around the corners, the faster you enter the next straight. If you have the run out of the corners, you are very difficult to catch and pass. When you race, you are always watching relative speeds at various places around the circuit. It also depends a lot about who gets in your way when you are coming through. In some races, nobody has a handling advantage, so it becomes a power game. In the old days two-stroke races were like that. MotoGP is often a procession - they all do the same thing in corners.
The only thing on my bike which is not lighter than normal are the cast iron cylinder barrels. A heavy bike has more effect on the side-loading on the tyres as you turn.

SteveA said:

Lately I have been wondering if an A65 motor can be shoehorned into the BSA Fury (Triumph Bandit) chassis I have in place of the SR500 Yamaha engine that is in there!

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Hi All,
I give up? I didn’t know the Bandit or the Fury ever got into production.
How many were sold?
We’re they any good?
Were they a case of too little, too late?
Could they have significantly changed the plummeting trajectory of the British bike industry?
I believe a lot of hopes were pinned on them, a pity they didn’t continue in production

On another note, BSA A65 etc have been mentioned in glowing terms in this thread. They were never really on my radar as a kid in the late seventies. Most of what I know about them involves them having a significant main bearing fault (that is fixable with a modification) and that in popular culture they seemed to play second fiddle to both Commandos an Bonnevilles.
It seems I might be wrong on these assumption based on the content of this thread. So inspired have I been that I have watched a series of YouTubes from a site called Classic Motorcycle Channel about rebuilding a BSA motor. I must say the engine looks very well built and more modern in design than both Triumph and Norton.
Apologies for leading this thread somewhat ‘off topic’ on a dedicated Norton forum but it is exceptionally interesting (to me) and the history of all British’s last ‘big three’ motorcycles does seem integrally tied together.

As a last comment I do find it a little confusing how much the actual straight line performance of the Commando varied over it’s production life, over the years being described in road tests as absolute road burners with ‘low twelves’ on the quarter and terminal velocities of over 120mph in comparison to being referred to anachronistic (Mk 3) loping tourers with modest performance with quarter mile times in the high thirteens and barely capable of getting to 110mph (I do understand the Combat debacle). This thread has certainly taught me the importance of weight reduction in obtaining performance
As for me, I have to put reliability above horsepower but I do want the bike to perform as well as possible, after all that’s why we ride these bikes

regards Al and thanks for the varied and interesting information provided.

The MK3 was choked by its stock restrictive exhaust.
I once bought a Vincent with a very restrictive silencer in place. It was a correct replacement item but made for folks who like a really quiet exhaust note.
After reading all the tests and hearing all the stories, I had to see how fast one of these legendary Vincents would go.
83 mph was it! What a disappointment.

Drilled out the exhaust, rejetted the carbs and top speed went up to 115 mph. Acceleration changed in the same way.

That stifled exhaust killed the MK3 performance.
Meanwhile the competition had made their bikes a lot more powerful by 1975.
The 68 Commando would have had a tough time against the 1975 crowd.

Glen

Hi Alan
There were only a dozen or so Bandit Furys made. However the pre production had started & there may have been a few hundred frames made.
Edward Turners original design was fragile & it would have probably been a warranty disaster.

worntorn said:

The MK3 was choked by its stock restrictive exhaust.
I once bought a Vincent with a very restrictive silencer in place. It was a correct replacement item but made for folks who like a really quiet exhaust note.
After reading all the tests and hearing all the stories, I had to see how fast one of these legendary Vincents would go.
83 mph was it! What a disappointment.

Drilled out the exhaust, rejetted the carbs and top speed went up to 115 mph. Acceleration changed in the same way.

That stifled exhaust killed the MK3 performance.
Meanwhile the competition had made their bikes a lot more powerful by 1975.
The 68 Commando would have had a tough time against the 1975 crowd.

Glen

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The 850-750 thing makes me smile a bit. An extra 10% capacity ought to improve output, all else equal. I'm not versed in differences in head internals etc. Possibly that makes a big difference? But as for the obvious limitations of an 850 straight from the factory: Like most 850s now, my stock silencers are probably a pile of brown dust somewhere. Replaced with 750 lookalikes (with balancer). Air filter now K&N. Again, I doubt there are too many stock mk3 air cleaner systems now.

So, not sure why my 850 (828cc) would be slower than a 750. Ah, the weight of a starter motor... really?! If a few pounds(?) makes such a big difference, wouldn't we all replacing our batteries to lithium, be into really lightweight riding gear and losing a couple of inches from our midriff?

They made a mistake designing the 350 head and had no room to get a good port shape. Management would not allow them to correct it? It gave a best of 34hp after all they could do, on par with the cheaper established Honda. It had very good running gear and a frame second to none. With the ports corrected with alteration to the head casting 45hp should have been easily available, they had no lack of expertise with designers and engineers. The lack was higher up the chain. Which must have been a great let down to those involved.

You can imagine what that extra power would have done for marketability had they had it. Greater hp and GP style frame could be sold at a premium, but parity with a cheaper proven product would be difficult. Management should have understood. Kawasaki understood when Honda introduced the 750 4, they waited and enlarged their pending 750 to 900 so their dominance was emphatic. At least on paper, because both those 4s carried a lot of weight. The lighter good handling products from Britain, like the Commando's had their advantages. Well exploited by Peter Williams and others.

Alan L said:

I give up? I didn’t know the Bandit or the Fury ever got into production.
How many were sold?

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It never made it into production, about 35 of assorted mock ups with no engine internals and running prototypes were made. However they did place orders for parts and ended up with 1000 frames, these were eventually scrapped but in the scrapping process a few got over the fence and then once BSA were no longer around to object made it into sales.



And if you spend long enough tracking down spares or modifying other BSA/Triumph parts you can build your own.

This one took 7 years.

https://www.youtube.com/channel/UChcm2PQTw_OnMZt1F1otNjQ

kommando said:

It never made it into production, about 35 of assorted mock ups with no engine internals and running prototypes were made. However they did place orders for parts and ended up with 1000 frames, these were eventually scrapped but in the scrapping process a few got over the fence and then once BSA were no longer around to object made it into sales.

And if you spend long enough tracking down spares or modifying other BSA/Triumph parts you can build your own.

This one took 7 years.

https://www.youtube.com/channel/UChcm2PQTw_OnMZt1F1otNjQ

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Ted Bloomfield at MCS had loads of these frames
My mate reckons he had about 200 in his yard?
Such was the quantity of Ted's storage when I bought a brand new original roadster tank in about 1981 he had over 50 factory seconds to choose from, I picked out a black and gold pinstripe one that had a tiny dimple in the paint
I can remember people buying fastback tail units from him just for a pair of reflectors apparently!!!

Alan L said:

Hi All,
I give up? I didn’t know the Bandit or the Fury ever got into production.
How many were sold?
We’re they any good?
Were they a case of too little, too late?
Could they have significantly changed the plummeting trajectory of the British bike industry?
I believe a lot of hopes were pinned on them, a pity they didn’t continue in production

Click to expand...

Yes, we are off-topic.....but..... If admin want to move this fine by me, but I am also happy to stop here on the BSA topic.

No, the Bandit/Fury did not make production, but by the time it was cancelled a batch of frames had already been made, and some other parts. Those that exist have been mainly built from those parts by determined individuals.

Somehow, the frames ended up distributed around the UK Midlands, many laying in sheds for decades. The frame design has been referred to as a mini Rob North, even if said gentleman had absolutely nothing to do with it. With a strengthened swinging arm mounting it has been used by several racers. Mine was converted to monoshock. I can only tell you that few bikes I have ridden turn as quick and are stable in a straight line, I found mine an absolute hoot to race. Was the original design capable of this? I don't know, but the reputation is good based on those that exist.

Would it have saved the industry, no. The engine design had flaws, and it would have been difficult to maintain. Like many things, it was positive, but too little too late. It was a move towards what Honda were doing, but still fell short and would have needed several stable mates from 250cc to 1000cc to address the market. And a few below 250cc to capture new riders to the brand.

The A65 was a fairly good design, and they were bikes that grew on you. I think they were easier to sell to established BSA people.

The A65 did suffer as you say from a poor main bearing solution, not that anybody ever mentioned it at the time!

Yes, that can be fixed today, and should be if you want to run it hard.

I enjoyed my A65, but I enjoyed my Fastback more.....because I did a lot of different things with the Fastback! And it was good at them all.

baz said:

Ted Bloomfield at MCS had loads of these frames
My mate reckons he had about 200 in his yard?
Such was the quantity of Ted's storage when I bought a brand new original roadster tank in about 1981 he had over 50 factory seconds to choose from, I picked out a black and gold pinstripe one that had a tiny dimple in the paint
I can remember people buying fastback tail units from him just for a pair of reflectors apparently!!!

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Ah Ted, that brings back memories

Mart UK said:

The 850-750 thing makes me smile a bit. An extra 10% capacity ought to improve output, all else equal. I'm not versed in differences in head internals etc. Possibly that makes a big difference? But as for the obvious limitations of an 850 straight from the factory: Like most 850s now, my stock silencers are probably a pile of brown dust somewhere. Replaced with 750 lookalikes (with balancer). Air filter now K&N. Again, I doubt there are too many stock mk3 air cleaner systems now.

So, not sure why my 850 (828cc) would be slower than a 750. Ah, the weight of a starter motor... really?! If a few pounds(?) makes such a big difference, wouldn't we all replacing our batteries to lithium, be into really lightweight riding gear and losing a couple of inches from our midriff?

Click to expand...

When comparing road bikes remember this was a period when new US environmental laws were killing the performance of most existing designs, cars or bikes. So you are not comparing apples with apples. Most of the development work went into meeting new regs and not losing too much power.

But looking for the answer to your question, I think it is quite simple, the limitation is in the cylinder head, porting and valves. Stock port and valve sizes remained the same, and could not flow any more. (And the standard cam didn't change either.)

Way back when I built my first race motor and had a bunch of ex-works parts to play with, big valves changed things, but....

Thruxton had race motors with big valve heads etc. on the dyno and noted huge extra power from an 828 compared to a 750 long stroke at 4000rpm reducing to pretty much no extra power at 7000. Most race 850s of the period did not rev past say 6800. But, they didn't need to. The extra power lower down made them easier for most riders to ride faster! Mid-range is your friend on a race circuit. Drag racing does not in any way show the true capabilities of most Nortons, it is corner exit where most speed is gained on a race circuit. An 850 was better unless you were a very good rider.

kommando said:

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Interesting that Devimead, BSA people, called them ex BSA Bandit, when it was either BSA Fury or Triumph Bandit!

But I do think they got it more right than BSA Triumph did, rolls off the tongue better!

Nice that they suggest an A65 motor will fit....best start a search I guess!

If you cannot find one, the last frame on ebay was asking £5250 for frame alone, then Kawasaki did 2 copies which are good starting points, ER500 and the GPZ305, the ER500 is the bigger frame. I have a GPZ305 as a starting point for a P92 copy, BSA Unit Single with isolastics.

ER500 frame with T140 engine that FE found on UK Ebay.

Chris said:

The Bandit framed T140 looks like Tony Haywards old bike. Really nice bit of kit.
Just to play with this thread some more lol
Nige knows about this! Brought for a friend to relive his youth but he is to ill to buy it off me.

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I shouldn't ask, should I Chris?

In the old days, the only twin carb 650 twin BSA, was the Super Rocket. It was slightly faster then a Bonneville, but you would not play with one. There were not enough of them around. Even Norton twins were not as common as Triumphs. Even with Triumphs, you could not play with the 500s. They did not have proper timing-side bearings until 1973.

acotrel said:

They did not have proper timing-side bearings until 1973.

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As the last A65 was made in 72 how does that work, the Devimead conversion was not factory that does not count and anyway was available in the late 60's as the owner was using A65 engines in his racing sidecar.

There are two types of engine power - horsepower and torque. If you have a lot of torque, as you raise the gearing you diminish its effect. Nortons have the heavy crank, so throttle response is less. You need to keep the crank spinning high if you want to out perform bikes which have lighter cranks. A restrictive exhaust has a big adverse effect on high revs. When I started racing my 850, the only thing I found wrong was the ratios in the gearbox. The effect of changing anything else was minimal. Commando motors are fast enough without doing much to them.
DBD34 Gold Star BSAs have RRT2 gearboxes, which have an almost impossible first gear. Other than that they are much quicker than B33 BSAs which are also 500cc. The difference is in the gear ratios and not much else - even if you fit the race cams to both motors. 500cc Thruxton Velocettes accelerate faster than 500cc Venom Velocettes, and it is not because of the GP carburettor.
The problem is, if you fit the close ratios, you probably commit yourself to riding faster. The way you set the bike up has to suit the way you intend to use it. In traffic, wide ratios are better.