Actual cc of the 850?

[L.A.B.]

Norvil Motorcycles - 1000CC 2004 Fastback Commando

"We have already developed a 920cc version (81mm x 89mm), and a 952cc version (82.5mm x 89mm) and a whopping 980cc version (81mm x 93.5mm). What next we thought ........ well, our new 1000cc bike will combine the best of both worlds with a bore of 82.5mm and stroke of 93.5mm, to make a Commando of over 1000cc (1000.0325 to be totally precise)."

 

[Dan1950]

Then +0.080"

Engine

Engine

www.rgmnorton.co.uk

920cc

920 COMPREHENSIVE CONVERSION KIT

KIT COMPRISES OF:050016 - 920 CYLINDER LINER X2050163 - 920 PISTONS (COMPLETE WITH RINGS & CIRCLIPS) X2050207 - 920 GUDGEON PINS X2920HG - 920 COPPER HEAD GASKET050150 - 920 GOLD DECALS X2 (ALSO SILVER ON PART NUMBER 050149, BLACK ON PART NUMBER 050148 AND RED ON PART NUMBER 050151) PLEASE STATE

www.rgmnorton.co.uk

920+0.020"

920 PISTON KIT +20

RGM NORTON 050164

www.rgmnorton.co.uk

+.080 would be 872.497248922898cc

 

[gortnipper]

If you really want an 850 just bore it to +0.040" . (850.547) The extra performance will blow your mind!

I did and mine does.

 

[Mart UK]

I did and mine does.

I wonder. Even if an extra 2-3% capacity translates to the same increase in performance, would we notice it? It could be like changing tyres, my new ones always seem like a better tyre compared to the ones I had on. Forgetting they were squared off. Lost compression on old bores must damage performance.

 

[gortnipper]

I wonder. Even if an extra 2-3% capacity translates to the same increase in performance, would we notice it? It could be like changing tyres, my new ones always seem like a better tyre compared to the ones I had on. Forgetting they were squared off. Lost compression on old bores must damage performance.

Oh I forgot... flow ported FA head, highr CR pistons, hot cam, Maney exhaust...maybe it wasn't the extra 22cc..

22 cc on a moped motor, now that's a difference!

 

[Fast Eddie]

I wonder. Even if an extra 2-3% capacity translates to the same increase in performance, would we notice it? It could be like changing tyres, my new ones always seem like a better tyre compared to the ones I had on. Forgetting they were squared off. Lost compression on old bores must damage performance.

IMHO a normal person like us would not notice such a small increase in cc.

But, by definition, a motor needing a rebore will be suffering blow-by, burning oil, etc, so will not be performing well.

The extra cc of the oversize is also going to bump up static compression a little.

Also not many people would put a motor back together without de-coking etc.

So, the combination of an engine running better / cleaner, a higher CR, and a bump in cc will probably be felt.

But perhaps the biggest factor that will give an increased feel in performance… is… good old… placebo !

 

[gortnipper]

IMHO a normal person like us would not notice such a small increase in cc.

But, by definition, a motor needing a rebore will be suffering blow-by, burning oil, etc, so will not be performing well.

The extra cc of the oversize is also going to bump up static compression a little.

Also not many people would put a motor back together without de-coking etc.

So, the combination of an engine running better / cleaner, a higher CR, and a bump in cc will probably be felt.

But perhaps the biggest factor that will give an increased feel in performance… is… good old… placebo !

Logic. Pshaw.

 

[Staytite]

And there was me thinking the 828cc was the standard bore
with the 829cc version being for the big bore, cafe racer boys
who want to go much faster !

 

[cash]

Would be fun to have some side panel transfers made up with that.

Clearly Norton decided to use 828 coz the 9 would have been extra number to make and would have cost more

 

[concours]

Like the old Irish guy who's job was to ensure only 239 beans were packaged in every can of beans. Not one single extra could be allowed.

 

[baz]

Like the old Irish guy who's job was to ensure only 239 beans were packaged in every can of beans. Not one single extra could be allowed.

When I cooked my kids dinner I used to tell them I'd counted the beans to make sure they had an equal share
They never once asked me what cc my commando was!!!!

 

[cliffa]

Is this where the term "Giving it the beans" emanated?

 

[EstuaryBoy]

Perhaps this is where 'farting' back through the carbs originated???

 

[Staytite]

When I was about six years old....

Beans, beans, good for the heart
The more you eat, the more you fart
The more you fart, the better you feel
Eat baked beans for every meal

 

[MichaelB]

Have to admit when I first discovered my beloved 850 was only a 828, I felt deceived, let down and disappointed.
Only to discover it's a common occurance in the motorcycle world.
When I realized that +40 brought it to a true 850, I rejoiced.
Then I pondered, why didn't they do this originally.
Maybe, because it only leaves room for 1 overbore?
Then my brain went to, they originally engineered it to 78mm, then debored it to 77mm, to allow for multiple overbores!!!
This is the kind of useless minutiae my brain produces......

 

[Dan1950]

Oh I forgot... flow ported FA head, highr CR pistons, hot cam, Maney exhaust...maybe it wasn't the extra 22cc..

22 cc on a moped motor, now that's a difference!

How about a 30cc 4-stroke at 12.7:1 Compression running on methanol with 15% nitro methane? 1.8 Cu In producing 3.4 HP.