650 Norton Vibration and Balance Factor

You could work out how much power is wasted by rubber mountings by seeing how hot they get.

One horsepower would soon melt the lot!

Over the years a close friend has rubber mounted the engines in several racing Yamaha two strokes, they never seem to be as good to ride as with the original mounts, though the frames stop cracking. To my mind the best production Norton Twin was the 650 cc Manxman. After they got bigger the problems started.

https://www.youtube.com/watch?v=K2FWKO_81tQ

https://www.youtube.com/watch?v=lICP7S-jpvA

Triton Thrasher said:

You could work out how much power is wasted by rubber mountings by seeing how hot they get.

One horsepower would soon melt the lot!

Click to expand...

I recently had a discussion about the staggered crank, and the way the power is put down on the bitumen was mentioned. Perhaps the isolastics or rubber mounted engines changes the way the tyres recover after each pulse ? There is a reason that twin cylinder bikes are rarely used on speedway, or in MX.

acotrel said:

There is a reason that twin cylinder bikes are rarely used on speedway, or in MX.

Click to expand...

Thats sounds like the ole furphy again.
Remember when Kenny Roberts rode that TZ700 in dirt track, before they were banned.
Everyone said they could never work, a 4 cylinder 2 stroke could NEVER get traction.
He just cruised along, and absolutely blitzed em at the finish.
They banned em after that - made all the twins look pathetic ??

Remember too those Commando powered WASP outfits on MX tracks,
and the Ron Woods Commando powered flattracker winners in the US,
and the Yahahahaha XS650 motors in the US titles.

Selective amnesia/alzheimer's is great for ignoring reality.... ??

When did they ever run Harley or Norton flat trackers in the same race with as 500cc Jawa speedway bikes with European riders ? I think you are kidding yourself. And a TZ700 solo on dirt is simply stupid, you don't need that much horsepower on dirt. If you put a rider such as Kenny Roberts on it, of course it will get around fast. For anyone else it would probably mean a face full of splinters. My brother has an H2 Kawasaki engined sidecar outfit on methanol. It is as useless as tits on a bull, you just don't need that much power. The H1 is quite sufficient to beat anything else. These days our guys race sit-up sidecars with R1 Yamaha motors, and hold them on full throttle all the way round - the H1 is quicker. In a solo that stuff is stupid. Roberts was a brave man to get aboard it, did anyone else ride it ?
I love watching the videos of Harleys racing on the mile circuit, they are very spectacular, however what does that mean ? Perhaps you should invite four speedway solo riders from Europe over to the US, and check their lap times on your circuits ?

Perhaps we didn't realise you had strayed so far off the subject of 650SS Nortons,
and were being so selective with which type of dirt tracking we seem to have strayed into ?

Of course, Nortons and twins and TZ700's racing and winning on other forms of dirt track
just shows how selective you have to be to justify your comments.

BTW, rumour has it that the new H2R outputs more than 300 hp.
But we diverge, muchly...

We were discussing balance factor and I mentioned how it might the way the power is put down onto the ground. If you are used to only riding on modern tyres, you are probably too insensitive to recognise what your bike is really doing. When the tyres are rock hard with no grip, every slightest twitch is a problem which conditions you. Come and race against me in the rain sometime.

I think I should warn you that every time I go on a motorcycling holiday, it RAINS !!
So I have done more miles on a variety of bikes than I care to remember in torrents of water. :x :x
Dunno about racing in the rain though, that seems like a silliness I could do without.
From your descriptions of falling off a lot you sound like a real bunny, should be easy meat ?
If you can organise to make it rain on specified days though, many drought affected areas might like to hear from you....

I think I fell off at the first 5 meetings at which I raced - 45 years ago. After a while that doesn't happen any more and these days I go nowhere near crashing. In fact I take metoprolol (beta-blocker)for a heart condition and it stops the adrenalin rush, so if you have a moment everything happens in the cold light of day and you simply ride through it. If you believe you can beat me - come and try. We will pick a nice rainy day preferably after there have been historic races at Winton, so the surface is nice and greasy.
If I'm ever racing and it rains, I always know I'm in with a good chance.
It is all in the mind, if your concentration is fixed on the rear tyre contact patch all the time when it's raining, you won't usually crash unless you get silly. The problem with the new tyres is that you can usually give them heaps with impunity and it becomes a habit. These days I tend to do it myself and that is why a while back I asked on this forum if anyone has ever hi-sided a commando. The other thing about falling off in the rain is that if you watch where you get a bit careless, you don't usually get hurt. (Always stay right away from solid objects). So I usually get stuck right into it when the track is covered with water. Always remember - if it is bad for you, it is bad for everybody else. I really like those plastic coveralls.
The thing about the Seeley is that it is very predictable and safe as long as you are aware of how it steers, so I have no anxiety whatsoever about racing it. That was never the case with my old Triton, it would crash you anywhere and everywhere. My friend owned it in the 50s and was an excellent rider - it did a really big number on him at Bathurst which I didn't find out about until fairly recently.

acotrel said:

Phil Irvings Tuning for Speed tells you how to do it, all you need is your wife 's good set of electronic kitchen scales and a level. I think you will enjoy doing the exercise, but be careful if you need to drill the flywheel to get the desired factor - don't make a grenade out of it.

Click to expand...

Have other used this book Tuning For Speed and technique to determine balance factor?
Is this portion of the book Tuning For Speed posted online somewhere?
never mind, quick find on google

You were doing well to find those online.

It is possible to use that method to determine the balance factor of your engine.
By some careful weighings, and using bobweights, or other, washers etc, bolted/wired/glued to your crank,
the original balance factor can be calculated.

Be aware that getting the conrod perfectly horizontal and weighed at either end can be quite a variable process,
and the balance factor may vary accordingly.
Worn piston rings, carbon on the piston etc can all affect things slightly, although mostly insignificant.

Have fun !
And tell us how it goes, can't recall if anyone has quoted what the 650SS used as a balance factor ?

The man we love to hate, Les Emery, told me that 82% is the correct figure for a standard Atlas or 650SS.
Glen

I would have thought that the atlas would have heavier pistons and a lower peak revs for reliability, so the BF would be lower than for a 650ss

Since the balance factor has more to do with what cycleparts vibrate in sympathy with the engine shakes,
its not really surprising that about the same featherbed frame with the same engine mounting system
would require about the same BF Balance Factor.

If the frames had notably different length tubes anywhere, or different tank mounting systems,
or different engine mounting systems, or different design somehow, then it might be a different story.

But near identical bikes with near identical engines, it would be surprising indeed if they did have different requirements...