270 Question

nickguzzi · Nov 11, 2014

The Hinckley twins, either 270 or 360, have two balance shafts.
http://www.triumphrat.net/twins-technic ... awing.html

According to one racer with a bored and stroked 1200cc engine it was maybe worth an extra 4 hp.
Another thought it not worth the vibration and put his balance shafts back. "Shook like a Harley". What ever that means.

Chris · Nov 12, 2014

Hi Dave Watson has spent at least 4 years developing his 270 750 Seeley Mk2 framed Commando in classic racing.
I will ask him for his thoughts.

Chris

BritTwit · Nov 12, 2014

nickguzzi said:
The Hinckley twins, either 270 or 360, have two balance shafts.
http://www.triumphrat.net/twins-technic ... awing.html

According to one racer with a bored and stroked 1200cc engine it was maybe worth an extra 4 hp.
Another thought it not worth the vibration and put his balance shafts back. "Shook like a Harley". What ever that means.

That "racer" is doing something wrong.

You can buy a Magnum 1087 Bonneville motor from SouthBay Triumph that is very street-able, makes 125HP at the crank, and retains the twin balancer shafts so it is smooth as a stocker. They (SouthBay) have a more radical track cam that will make even more power. It's not cheap horsepower, but this kind of power can be had with a Hinckley twin.
It is a greatly under appreciated mill.

Harleys, other than the EVO motors, shake like hell. It's what they do well. :lol:

Tintin · Nov 12, 2014

BritTwit said:
Harleys, other than the EVO motors, shake like hell. It's what they do well. :lol:

My rigid mount 1200cc Shovelhead is smoother than my rigid mount 750cc Atlas .... :wink:

Tim

cyclepsycho · Nov 13, 2014

The 270 crank is supposed to run smoother (supposed to).
If your really want it to run smoother then use the JSmotorsport lightweight pistons and longer rods.

Diablouph · Nov 13, 2014

What carbs?
What ignition?

An 850, primed, with a good electronic ignition should tick over on the first or second push off from TDC. I hope you were kidding about the jumping, or something is going to break.

I would check that you have fuel IN THE CYLINDERS, and that the ignition is timed WITH A LIGHT.

I had hard starting for two years. Blamed everything (except myself), then I hooked up my timing light that I had never used, and ...............7 degrees off.

BTW, how does an ignition work on a 270 crank?

Hobot · Nov 13, 2014

In direct bolt on engine cycles the primary harmonic is way worse than the horizontal so 270's are smoother in those but wonder if isolastics can isolate that annoyance. http://victorylibrary.com/brit/offset-c.htm

midnightlamp · Nov 13, 2014

Isolastics can't take a rocking couple well as there is a sideways clearance on the lower mounts that would need to be removed. They are primarily designed to handle a reciprocating in plane motion such as what you'd get from a 360 twin or a single.

Diablouph · Nov 14, 2014

Say, aren't we supposed to be helping Norsa1 get his bike started?

SteveA · Nov 14, 2014

midnightlamp said:
As for the Norton......................

People often forget that the reason why people liked parallel twins and singles is the power delivery and the reasonable vibes. A dynamically balanced single/twin is a very reasonable ride if set up right and I doubt anyone would really complain with a competently set up low displacement one, within a reasonable rev-range. Take away the simplicity...and you loose a lot of the good.

Norton, and all of the other British manufacturers liked parallel twins mainly because they could build a twin for not much more cost than a single....unlike V twins that need two cylinder and cylinder head castings and all of the associated machining....

And when they started doing it in significant volume post WW2....the customer didn't know any better....for most buyer the choice was a single, a parallel twin, or nothing.....for sure old JAPs in various forms were around, but very few could afford a post war Vincent....

The comparisons we make are with the value of hindsight and alternatives that didn't exist for most buyers.

As for helping the OP with starting his bike.....apart from advising that he gets the ignition set correctly and learns the best technique for getting the thing primed and set before the swing.....and maybe changing the actual kickstart lever for one with better mechanical advantage....they are readily available.....the only thing I can add is pasta....and plenty of it....an extra 30lb might help.

If that doesn't work.....buy a roller starter....mine is being delivered next week..... :wink:

Diablouph · Nov 15, 2014

Or just buy a house on a hill.

SteveA · Nov 16, 2014

Diablouph said:
Or just buy a house on a hill.

SteveA · Nov 16, 2014

Diablouph said:
Or just buy a house on a hill.

But I should anyway, at spring tide the garage here is below sea level, and it is only 250 yards away....

Rohan · Nov 16, 2014

SteveA said:
But I should anyway, at spring tide the garage here is below sea level, and it is only 250 yards away....

Ocean views, in real estate parlance....

norsa1 · Nov 17, 2014

Nope. All this pontificating and the bike is still difficult to kick over.

We can discuss the merits of a 270 degree engine in another thread. Suffice to say I did the conversion because the engine is solidly mounted into the frame and I was striving for a smoother engine.

The journals are 270 degrees apart and I believe that what is happening is that when the lead cylinder is firing the other cylinder is a quarter rotation behind. This cylinder is is also on compression, is that a double compression stroke I am trying to kick through. Not sure about this

BTW the ignition is handled by Power Arc. Told them what I wanted and they programmed the module.

Rohan · Nov 17, 2014

norsa1 said:
The journals are 270 degrees apart

norsa1 said:
and I believe that what is happening is that when the lead cylinder is firing the other cylinder is a quarter rotation behind. This cylinder is is also on compression, is that a double compression stroke I am trying to kick through. Not sure about this
.

That could only happen if the 2 cylinders were only 90 degrees apart.
And were set to fire as a big bang configuration, both firing on the same stroke !

Did you see the camshaft ?
The bumps on each cylinder would all be clustered togther, not spread around the cam.

Why not try part of what the old time racers used to do.
Snick it into gear, roll it backwards until compression stops it,
snick it back into neutral
and then try kicking it.

Checked your ignition timing carefully ?
Having the timing too far advanced can cause very difficult kicking, even on a stock Commando.

Hobot · Nov 17, 2014

older Chevy V8's with cherry bombs sound identical to classic Harleys. Yamaha gave Rossi 5 combo's of various crank shaft and fire orders and digital controls, he picked 90' crank and least interface and won a handfull of years on it. Read it in Cycle World last month. There's comfort frame reasons and then there's hook up control reasons and plain old experimenting. Does anyone know the crank angle of the Norton V4 custom?

Rohan · Nov 17, 2014

hobot said:
Does anyone know the crank angle of the Norton V4 custom?

V4 Custom ??

You referring to the Aprilia V4 in the IoM Racing "Nortons" ?
Its a stock Aprilia race engine, supplied as delivered from Aprilia.

Given that Aprilia wrapped up another World Superbike series win a few weeks back,
narrowly over that Kwikasaki it must be said,
that engine has some serious mumbo on a well sorted bike.
Its 'a narrow angle 65 degree V4, only 220 mm wide,
with intervals of 0°, 180°, 425° and 605°
78mm and 52.3mm bore and stroke, 48 mm throttle bodies.
Thats what the publicity says anyway, whats in that WSBK screamer is anyones guess.

If Nortons can half make it go like that, it should give a good account of itself...

SteveA · Nov 18, 2014

Rohan said:
Why not try part of what the old time racers used to do.
Snick it into gear, roll it backwards until compression stops it,

Shit, I ain't that 'old time' am I? ;-), OK I learnt it in teh '70s, but I pulled it back on compression last year, when begging a push in the holding area and away from the starting rollers.....

It is an effective technique....

Rohan · Nov 18, 2014

SteveA said:
It is an effective technique....

Its been known about since pre 1900, so we shouldn't be offending anyone with that old time racer quip ?!

270 Question

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