Why a [360°] parallel twin?

I have always owned 360 swing cranks in all my British bikes they put out that nice thump to the engine and exhaust pipes, pull like a train, good engine braking but not as smooth running, I thought I would never have any difference in other than a 360 swing motor, my new 2013 Triumph Thruxton with TOR mufflers sounded great and went well and with a 360 swing but I decided to take a new Triumph Thruxton 1200 with the 270 swing and lighter crank (HP motor) I was hooked, never thought I would, completely different sound with lost of that thump to the note, more torque down low and midrange right to the rev limiter, a lot smoother but lost of that engine braking when backing off, I love my old Norton (over 46 years ownership) but my 270 swing Triumph Thruxton (with Meerkat x-pipe and opened up stock mufflers) is even better, love the torque and smoothness and great for long distant travels, I sold the old Thruxton with the 360 swing as I was not riding it after buying the 1200 Thruxtonm my Norton is now semi retired, my Thruxton 1200 is my everyday ride but I also love taking my old Honda CRF450X dirt bike out its like having a V8 strapped to your legs, so quick and powerful for the bush.
As for the Japanese road bikes just don't have that thump like a good Bristish bikes with a 360 swing crank where both pistons going up and down together.
Back in 76 I did buy a old TX 750 Yammy, it was a pig of a bike and sold it to buy my new Norton 850 2 weeks later, I was 17 years old.

Ashley

Ashley,
That's interesting what you said about the TX Yam. I've always wondered what they are like to ride, as I think the are a really nice looking bike, especially in the gold finish. From what I've read the earlier ones had oiling problems, but that was sorted on the later bikes.

Martyn.

The Norton 961 variants have 270 deg cranks.
My friend says my 961 Dommie sounds like a Ducati

Hi All,
Whilst somewhat off topic, my youthful memory of the 750 Yamaha twin was that it was one of the few Japanese bikes that had a truly bad reputation. Poor reliability and little to make it standout from the crowd when they was going. I don’t know what their performance figures were but they were not regarded as fast.
This is in contrast with the majority of Jap bikes which might come in for various criticisms, poor handling, frame hinged in the middle etc but we’re still recognised as quite advanced, reliable and fast bits of machinery, not that us few pommie owners would care to admit that.
Bikes like the Suzuki rotary were seen as just dam quirky and their water cooled 750 two stroke received rather unflattering nick names like ‘water bottles’ or ‘chicken boilers’ but deep down we knew just how good they were. The Yammy 750, as I said, that was a different story, I think we felt rather sorry for their owners.
Quite why one would have bought one new, I have really know idea? I would have thought that a Honda 750/4 would have eclipsed them and a Kwaka 9 would have been a light year beyond.
Left unmentioned in this little chat is the venerable Yamaha XS/TX 650. It was always seen as a rather righteous bike. Simple, effective and good looking, without the ‘bells and whistles’ in the way of balance shafts etc. just a good old vertical 360‘ twin. Dare I say, it was often described as British twin done correctly, again we would have never said that but it would be hard to refute. I’m sure a good Triumph or Norton would have been a quicker and better handling bike but hell, for the average lad they were strong, simple and reliable with many of the charms of a Bonnie with a dam sight less oil leaks and lower maintenance requirements. Yes, they too vibrated at higher revs but I suspect less than our bikes did through better design and factory balancing. A lot of good miles were put on those bikes by a lot of riders during their long production run.
just a thought or two
alan

speirmoor said:

The Norton 961 variants have 270 deg cranks.
My friend says my 961 Dommie sounds like a Ducati

Click to expand...

Indeed they do, especially on decel.

Matchless said:

Ashley,
That's interesting what you said about the TX Yam. I've always wondered what they are like to ride, as I think the are a really nice looking bike, especially in the gold finish. From what I've read the earlier ones had oiling problems, but that was sorted on the later bikes.

Martyn.

Click to expand...

There is MUCH MORE to it.

speirmoor said:

The Norton 961 variants have 270 deg cranks.
My friend says my 961 Dommie sounds like a Ducati

Click to expand...

If your Ducati sounds like a 961… put some sawdust in the oil and sell it quick…!

To me, a Kawasaki 900 felt like a 350cc British bike. They were fast in a straight line - I used to race against them in Allpowers races. At

Fast Eddie said:

If your Ducati sounds like a 961… put some sawdust in the oil and sell it quick…!

Click to expand...

With a 270 degree crank, it must be very difficult to play with cam timings. People have suggested I should make a 270 degree crank for a Commando. I think I would be outsmarting myself, if I did that. Some guys have never tried to optimise a motor for performance. Balance with a race motor is never a problem. For a road bike, low speed vibes are not good. You need to decide whether you want a sports bike or a commuter. I don't think many people ever try to make a Japanese bike really go - what would you do with it ?
I was involved in fitting a race cam into a Z1R Kawasaki for Bathurst. Most guys used Yoshimura, but the cam I fitted was Italian. Top end power was never problem with big Japanese bikes.

concours said:

There is MUCH MORE to it.View attachment 99247View attachment 99248

Click to expand...

Yeah that is the one I had, they look good, handled bad, felt heavy, not a high performer, electric starter didn't work and get a wifi of rain or water and it wouldn't start, it was a pig of a bike but I got it cheap and sold it 2 weeks later for more money than what I paid for it for a good deposit for my new 850 Norton only had to borrow $1100 ($1999 all up for my new Norton on the road) I paid it off in 9 months not bad for only earning $60 a week.

Ashley

I am a bit hazy on dates. But back then , there was a 500cc Yamaha which was the first bike to have a twin disc front end. The TZ350 A had the Fontane copy drum brake. John Maher was the fastest guy at Calder Raceway. He got the front end off the 500cc Yamaha and fitted it to his TZ. I watched him out brake every other rider. Three of them fell off while trying to brake into corners with him. I think the 500cc Yamaha was the TX500. It was ahead of it's time.

ashman said:

Yeah that is the one I had, they look good, handled bad, felt heavy, not a high performer, electric starter didn't work and get a wifi of rain or water and it wouldn't start, it was a pig of a bike but I got it cheap and sold it 2 weeks later for more money than what I paid for it for a good deposit for my new 850 Norton only had to borrow $1100 ($1999 all up for my new Norton on the road) I paid it off in 9 months not bad for only earning $60 a week.

Ashley

Click to expand...

I rode that TX750 up across TN 421 (steep mountain, tight switchbacks, called the "snake") three dozen times, and my Commando 850 nine dozen times, but, the TX was every bit as fast across the mountain, Shady Valley to Mountain City, TN

Ive always wondered why theres nobody tried removing this THING ,
tho Id always assued the THING was open backed onto the head face.
So its not as appaling as Id presumed .

BUT you could fit dual 'unbalanced 'headers on one . Obviously .



Seems it'd flow a lot of heat back ONTO the head . And prevent fresh air from cooling the head proper , like .



Ere Look. Cor , its gotta free sixty degree crank , like . Eh ! .

Hi guys, with all the inherent issues with a parallel twin engine design over a 180 degree twin, why did Norton & indeed the majority of the British motorcycle industry go down the parallel twin road??
I cant believe the technology & tooling wasn't available at the time so was it down to cost or just dog headed management?

Click to expand...

BALONEY !

As like somebody said , EVEN distribution of 'CHARGE '. ( unlike a Hardly Ableson - bar a dual carb or dual injector )


Twin CaM . GEAR DRIVEN INTERFACE . ( Like a TRIUMPH ) so as to allow more accurate control . Of valve timing .

One must remember that most journalists are concieted ignorant uneducated snots , endevouring to make others appear inferior , like polititions . who are stupid enough to talk to them .
THAT essentially was instrumental in the olde pommey garbages demise . It was still better built than the cheap stamed out japanese trash .
After all , if theyed charged double the price , where would we be ?

========================================================================================================================================

RIGHT .

You can get into all sorts of arguments about anything , like apples & oranges . Some things have certain ATTRIBUTES .

Any 'finite 'component is subject to elastic deformation . ( Plastic is when it premanantly deforms ) if you look at a TRAMPOLINE ,
its evident that its characteristics are favourable for certain purposes and TUNEABLE . Like a Violin , or Drums . Mainsails & the like .

Which is where Individuals with generations of experience have a intuitive understanding unavailable to cheap snotty dipsomaniac jurno types .
The younger snotty workers were getting that way too , though . we must admit .

how did you know it was a TX 650 or a Triumph ? If it was a Yamaha , it sounded as if it was going twice as fast as it was . Due to the 180 Deg. crank . !

The COSWORTH two Main Brg. crank runs up around 11.000 rpm's . So theres no NECESSITY to dispose of the ADVANTAGES of the Two Bearing Crankshaft .
Providing its dimensionaal displacement ( flexure ) is not excessive so as to cause misalignment . And is inside the plastic / deformation safely .

ANY Racing Crank at full whellie use , is usually LIFED at around 60 hours . Be it Triumph , yamaha , honda etc etc .
Even TRIUMPH valve gear is capeable of opperating past 10.000 rpm safely . SERVICEABILITY in the Pre detergent Oil Era , was mandatory . when you had the HEAD OFF
each year to DE COKE .

Anyone racing a 'new thing 'where your hard at it , will be repeatedly stripping it down for inspection , servicing , and looking for FLAWS & IMPROVEMENTS .
All the 'Modern Shite 'has been learned / picked up / accumulated , over time .

Theres a 1911 odd DOHC 4 - valve .


And another a darn site more visually attractive than most modern ad hoc contraptions .

And a FERRAI 2.5 litre Two Cylinder ( 360 & 180 cranks tried . But Not isolastics ! ) .




Should work good in a Commando .

If two cylinders are good enough for Rolls Royce , its hard to see why youre complaining .

You really must stop it @Matt Spencer or you'll surely go blind!

A few years ago Triumph built a Bonneville and a Tiger with the same motor (850 I think) the Bonneville had a 360 degree crank and the Tiger had a 180 degree. Everything else was basically equal from the article I read. The Tiger would beat the Bonneville in a 1/4 mile but the Bonneville had about 20mph higher top end. Go figure.

concours said:

I rode that TX750 up across TN 421 (steep mountain, tight switchbacks, called the "snake") three dozen times, and my Commando 850 nine dozen times, but, the TX was every bit as fast across the mountain, Shady Valley to Mountain City, TNView attachment 99270

Click to expand...

I just didn't like it, it was my first ever road bike after only having dirt bikes, it was cheap and I didn't have it long enough, 2 weeks only then sold it to buy my dream bike my Norton new, a mate of mine was able to get it to do wheel stands on it but was a bit heavy in the front end to get it up very far off the road, + I was a very skinny 17 year old at the time, but I made money off it and I bought a better bike which I still own.

Ashley

When I was a kid Triumph 650s were common and Norton Twins were rare. My mate had a Manxman and it was excellent, but most Norton Twins were 500s with single carb. They handled very well but were a bit slow. In those days, a lot of us obsessed about road racing. If you bought a Manx, you were almost immediately promoted into A grade. I always believe in Norton, because of their racing record. The cylinder head on the Commando, makes much more sense than a Triumph Bonneville head. When the Commando was designed, it needed to compete with the CB750 Honda for commuter sales. Most people did not need a fire-breathing sports bike.
If I had designed the Commando, Norton would have gone broke even sooner. The hole in the bob-weight and the isolastics are naff. If it vibrates, raise the balance factor and ride it faster. Japanese bikes are for tootling around town, and screaming away from traffic lights - not riding at moderately high speeds on long winding roads.
The only modern bike I have ridden was a VTR400 Honda, It was speed limited to 180 KPH - what is the point of that ? At 180 KPH, you still lose your licence and cop a big fine, so you might as well go fasrter.

motorson said:

A few years ago Triumph built a Bonneville and a Tiger with the same motor (850 I think) the Bonneville had a 360 degree crank and the Tiger had a 180 degree. Everything else was basically equal from the article I read. The Tiger would beat the Bonneville in a 1/4 mile but the Bonneville had about 20mph higher top end. Go figure.

Click to expand...

20mph on the top is a LOT. It would be fascinating to see a magazine road test comparo.

GEARING .