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Well'ard Rocker
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Originally Posted by DavidP
It's an American thing. The same thing happened with VWs, an engine which red lines at 5000, if that. We just can't stand the idea of revving the engine past the sloth of a big V-8.
Trust me, you're not getting better mileage, the best mileage I ever got was when I kept the engine above 5000rpm all day.

Yup. As I mentioned above, my Guzzis get better gas mileage on a long trip when I cruise a gear lower than most people.

My observation from years of reading comments in bike magazines (especially the old chopper mags), and listening to people sitting around BS-ing, is that people don't run their British bikes at high enough RPMS to keep from wrecking them because so many people in the old days were Harley wanna-bes.

After the days in the late 60s when you could bring a can of gas, a tire pump, and a battery and ride a police-auction Harley panhead off the auction lot for $300, and Harleys got really expensive, all these guys bought cheap-as-chips Triumphs and BSAs, stuck on extended tubes and a bolt-on hardtail, and went chugging around pretending they were on a Harley. A lot of those habits carried on .....

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In the 1930s people in Britain were driving around in four cylinder Austin Sevens with two bearing cranks. I’m sure neither Turner nor anyone at Triumph gave a moment’s consideration to a centre bearing. Why would they?

Yes, by the 1960s, they were hanging on to a 1930s design while Honda was building modern engines in modern factories.


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And in the late 1960s Triumph was still winning races with "that old 1930s design."

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Originally Posted by Irish Swede
And in the late 1960s Triumph was still winning races with "that old 1930s design."

And from there they went from strength to strength and destroyed the so-called threat from oriental manufacturers.


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well, there was that part . . .

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Originally Posted by DMadigan
Auto Union had a V16 SOHC roller bearing engine in 1934 but economics of the times and target market dictated the two bearing crank.
.
I just read about that car. It helped to have Dr Porsche design it and Hitler pay the bills.


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...in my opinion, just too many decades talking about how good the Japanese did it; however, is comparing Apples to Oranges...a 4 cylinder 16 valves car design made with better tooling cannot be compared with an old twin.
If you compare Apples with Apples; you would see that the Japanese twins were not better than this 1930 s design; even now are not better than new Triumph or other Euro brands.
Nobody talks about the other Euro brands; seems that always are the Japanese brands and Triumph.
The other day for the first time I see a 79 Honda CBfour 750 on the road!. Seemed that the guy just rebuilt it; have that classic Triumph look but with more power and less quality on the details and materials.
The performance is not so incredible for such big engine. The constant riding speed is a bit more (or the same) than with a Triumph 750 twin

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The clincher then was a working electric start.

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disc brake, too.

and four pipes.

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And for less money than a Triumph Trident.

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Look at NASHCAR, they are still winning with at least 50 year old designs. But then that is all they allow. Toyota had to make a special pushrod engine in order to compete. And the bore/stroke, cooling, head chamber, et cetera, all had to be within the parameters of a 50 year old design.
By the way, you do not want to run these old Brit engines at too low an RPM because you do not have vacuum retard and full advance at 3000 RPM is probably too much with modern fuels.

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Sounds like the way Harley (and the old Indians) kept their monopoly of AMA racing in the USA:
Force your competition to continue using your 50-year-old flatheads or penalize them to use 2/3 of the engine displacement if they want overhead valves.

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"And the bore/stroke, cooling, head chamber, et cetera, all had to be within the parameters of a 50 year old design."

The top photo is a 1970 Chevy head used on high performance engines and the basis for Nascar engines..In 1970 the engines were production based

The lower photo is the current Chevy Nascar head . engines are built to a formula like most other motor sports... The combustion chamber is a two valve wedge but otherwise shows no resemblance to the 1970 head.
5.7 liter Nascar engine rules restrict the HP to about 750 -800... Unrestricted these 50 year old design pushrod engines can make 900 hp at 9000 rpm for hours . Not the same as smaller displacement 4 valve engines but not too shabby either..
On the other end, new 1000-1200 cc sport bikes are making 200 plus hp with all street legal equipment..200 hp per liter on pump gas is very impressive...

93BE6885-2641-47A4-9555-1A386654FDDB.jpeg 66C7FBA0-CD3F-48C6-A6AB-8D849F9321C4.jpeg

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wahoe, what happened to the combustion chamber? Concave pistons? It's hard to tell if the center is milled at an angle or not and if so how do you put a gasket on that? Could be a shadow?

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Chevrolet 348 and 409 heads looked something like this: no combustion chamber in the head itself.
The blocks were milled at an angle, so the combustion chamber was actually the top of the cylinder.

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The RO7 Chevy Nascar engine has a small chamber around the piston valve pockets but the block deck is perpendicular to the bore. You could say it's a modified Heron head. Rules limit compression to 12-1.


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Personally I think 6000rpm is a smart redline for any British parallel twin if you want to get the most miles out of it before having to rebuild the engine, the late Triumph 500cc engine being a probable exception.

If you have a fat wallet then you may not have a problem stuffing the engine with a bunch or hot-rod parts and rebuilding it or blowing it up on a regular basis, but I think 99% of those who ride are happy with a stock engine that will last longer than they are going to.


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I guess this question is still on topic... why do you exclude the late Triumph 500?

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---6000RPM in top gear in a later 750 is plenty of speed and all with these poor forks that cannot "stick" it to the road. At about 5000 I commute near 140km/h. I think the 7500 and up RPMs are for the race guys that yes; rebuild the engines every few races.

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Quote
I guess this question is still on topic... why do you exclude the late Triumph 500?

I’d exclude it too. I owned one. It was a revelation. I never had a rev counter on mine but it would happily scream and deliver power up high the way a 650 of similar age won’t.

It’s an over square engine. Short stroke but wide bore. Piston acceleration and deceleration is not as dramatic as a long stroke, therefore kinder on the crank.

It’s a 500 so pistons and rods are lighter than the bigger Triumphs.

Low torque available at low rpm but a definite lift in response at about 4000rpm.

A short stroke engine is shorter meaning more room upstairs for valve and rocker magical engineering. The late 500 makes its power in the head and the flow through the combustion chamber.

It was an engine at the peak of its development and didn’t really develop after 1969 I think.

Often faster in third gear than in fourth.


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I'm with Ginge when it comes to Triumph unit 500 performance.

I have had 650s as well as 500s, but the 500 Daytona is a real thrill to ride. They get a "second wind" when they hit 5000 RPM.
With that performance and quick handling, a 500 Triumph is all the "sport bike" I ever need.

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Yeah, the handling is another factor.

Such a well resolved frame gives you the confidence to use the rpms and work the motor in the sweet spot. Good brakes and nimble.

I miss mine, but I’m too tall to have the best of it. Sold it to a short guy who uses it as a daily rider.


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Originally Posted by Irish Swede
And for less money than a Triumph Trident.
The Commado also sold for less than a Trident. Either will beat the pants off a Honda 4.


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Originally Posted by Irish Swede
I have had 650s as well as 500s, but the 500 Daytona is a real thrill to ride. They get a "second wind" when they hit 5000 RPM.
With that performance and quick handling, a 500 Triumph is all the "sport bike" I ever need.
I only had a 500 for a short time, and it was a single carb. Still a fun bike.
The triples are the same way, they come alive at over 5000rpm, mine never sees under 4500. With the new Premiers it revs to 7500, and likes it. laugh
I can't say about my 650, it only has an OP gauge. But, I'm pretty sure that it usually runs at over 4000rpm.
If I wanted to loaf around at 3000rpm all day I'd buy a Thunderbird or an A10. Just because it can run there doesn't mean that it should.


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Originally Posted by DavidP
[quote=Irish Swede]
I can't say about my 650, it only has an OP gauge. But, I'm pretty sure that it usually runs at over 4000rpm.


Same. My tack half ass works. Says almost 0 at idle but goes up when rev so I add on about 1000 from what is indicated. I don't know, Anything over 3500 indicated I get scared as it feels like it stops pulling and sounds like it is about to come apart or burn up. Maybe it's all in my head but it does slow down on the pull.

Last edited by splash; 02/01/22 9:38 pm.
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