920cc with 270 crank

kommando · Jan 15, 2021

I will take some pics tomorrow of my setup, its a copy of someone else's so not original but shows the concept.

lcrken · Jan 15, 2021

Interesting build. Someone put a lot of work into it. Given all that, I'd expect it to be likely to have a big valve conversion too. Have you checked for that?

Ken

HanaAna · Jan 15, 2021

lcrken said:
Interesting build. Someone put a lot of work into it. Given all that, I'd expect it to be likely to have a big valve conversion too. Have you checked for that?

Ken

I'd say there is "lot" of room for bigger valves?

Fast Eddie · Jan 15, 2021

HanaAna said:
Can you share ideas how to do it properly on Commando engine? I once tried in the middle of the sump on Triumph, thats where you can lock the crank, and it was a disaster. Blowing oil out.

This is what I run on my 920. Best thing since squeezy ketchup bottles...

Reed Breather Kit

The Norton twin cylinder engine creates a serious amount of pressure in the crankcase as the motor spins. Over the years the factory attempted several methods to reduce this pressure – from a timed breather off the end of the cam on earlier motors, to a crude straight pipe from the timing chest on

nycnorton.com

gortnipper · Jan 15, 2021

HanaAna said:
Can you share ideas how to do it properly on Commando engine? I once tried in the middle of the sump on Triumph, thats where you can lock the crank, and it was a disaster. Blowing oil out.

This is the unit most guys are running
Made by Jim Comstock and used to be sold by CNW.

Reed Breather Kit

The Norton twin cylinder engine creates a serious amount of pressure in the crankcase as the motor spins. Over the years the factory attempted several methods to reduce this pressure – from a timed breather off the end of the cam on earlier motors, to a crude straight pipe from the timing chest on

nycnorton.com

gortnipper · Jan 15, 2021

Too quick Nigel.

gortnipper · Jan 15, 2021

You can also use one of these on the crank case vent tube.

PCV Reed Valve - Crankcase Breather

Color/Finish: Silver Material: Metal Dimensions: Overall Length: 86.50mm Width (at widest point): 28.85mm Engine Inlet OD: 14.15mm Engine Inlet 11.85mm Filter (Air) Outlet OD: 12.00mm Filter (Air) Outlet ID: 9.45mm Fits: Universal Note: Easy Installation (Linked Below)

www.mikesxs.net

I have had both and the Comstock design works better.

HanaAna · Jan 15, 2021

Fast Eddie said:
This is what I run on my 920. Best thing since squeezy ketchup bottles...

Reed Breather Kit

The Norton twin cylinder engine creates a serious amount of pressure in the crankcase as the motor spins. Over the years the factory attempted several methods to reduce this pressure – from a timed breather off the end of the cam on earlier motors, to a crude straight pipe from the timing chest on

nycnorton.com

Now this is a solution that appeals to me! Costs money, but isn't this the reason, why I go to dull work every day and get the € to be able to cut corners

Fast Eddie · Jan 15, 2021

HanaAna said:
Now this is a solution that appeals to me! Costs money, but isn't this the reason, why I go to dull work every day and get the € to be able to cut corners

Sure is!

Ideal to buy it whilst cases are apart so you can ensure it clears the internal sump baffles properly etc...

HanaAna · Jan 15, 2021

gortnipper said:
You can also use one of these on the crank case vent tube.

PCV Reed Valve - Crankcase Breather

Color/Finish: Silver Material: Metal Dimensions: Overall Length: 86.50mm Width (at widest point): 28.85mm Engine Inlet OD: 14.15mm Engine Inlet 11.85mm Filter (Air) Outlet OD: 12.00mm Filter (Air) Outlet ID: 9.45mm Fits: Universal Note: Easy Installation (Linked Below)

www.mikesxs.net

I have had both and the Comstock design works better.

I've seen Ducati reed valve welded straight on timing case on Triumph unit engine. Don't have first hand info how that works. Though in principal the best place to get the breathing out would be in the sump I guess...

Fast Eddie · Jan 15, 2021

HanaAna said:
Though in principal the best place to get the breathing out would be in the sump I guess...

My thoughts too.

Also great way of emptying oil back to tank from wet sumping...

gortnipper · Jan 15, 2021

HanaAna said:
I've seen Ducati reed valve welded straight on timing case on Triumph unit engine. Don't have first hand info how that works. Though in principal the best place to get the breathing out would be in the sump I guess...

CNW was the original vendor for the sump breather NYN sells.

There is also this one for earlier 750s

1972 Engine Breather Modification

Experience an increase in engine performance Eliminate persistent leaks at gaskets, seals, tach drives, head, crank case joints and more Lower the operating temperature of the engine oil The valve can operate consistently during a far higher rpm range than the Commando engine can ever reach The...

coloradonortonworks.net

And this one

One way reed valve crank case breather

Pumping out positive crank case pressure and leaving a slight negative pressure is a great way to eliminate oil leaks. This simple breather uses the proven stainless steel reed valve from the BMW twin…

jsmotorsport.com

kommando · Jan 16, 2021

My breather is a modified sump plug with an aluminium adapter plate to allow the XS650 breather to be screwed onto the bottom.

There is a tube inserted to allow the air to be pulled from above the oil in the sump plug and as its for an MK2a with the internal ledge in the way the top part of the tube is flexible. This flexibility is not needed in most cases and if the cases are apart the ledge can be cutaway and a fixed tube used.

HanaAna · Jan 16, 2021

kommando said:
My breather is a modified sump plug with an aluminium adapter plate to allow the XS650 breather to be screwed onto the bottom.

There is a tube inserted to allow the air to be pulled from above the oil in the sump plug and as its for an MK2a with the internal ledge in the way the top part of the tube is flexible. This flexibility is not needed in most cases and if the cases are apart the ledge can be cutaway and a fixed tube used.

I think this solution is brilliant! I'm definitely going to have something similar.

Holmeslice · Jan 16, 2021

gortnipper said:
CNW was the original vendor for the sump breather NYN sells.

Not correct: CNW always sold the excellent breather that bolts onto the back of the cases (also initially designed by Comstock).

The thread-in sump breather was designed and first sold in limited quantities by Jim Comstock, then licensed to NYC Norton exclusively.

But back to the OP's initial post - this is a badass motor. Maybe not for everyone, but whoever did this up knew what they were doing. Not a lash up job.

-Kenny

gortnipper · Jan 16, 2021

Holmeslice said:
Not correct: CNW always sold the excellent breather that bolts onto the back of the cases (also initially designed by Comstock).

The thread-in sump breather was designed and first sold in limited quantities by Jim Comstock, then licensed to NYC Norton exclusively.

But back to the OP's initial post - this is a badass motor. Maybe not for everyone, but whoever did this up knew what they were doing. Not a lash up job.

-Kenny

Apologies. I must have been muddling up two separate pieces and comments from Jim in my mind.

fiatfan · Jan 17, 2021

kommando said:
My breather is a modified sump plug with an aluminium adapter plate to allow the XS650 breather to be screwed onto the bottom.

There is a tube inserted to allow the air to be pulled from above the oil in the sump plug and as its for an MK2a with the internal ledge in the way the top part of the tube is flexible. This flexibility is not needed in most cases and if the cases are apart the ledge can be cutaway and a fixed tube used.

That is from Mikes XS in the US, do you know if they are available here in Europe?

Fast Eddie · Jan 17, 2021

fiatfan said:
That is from Mikes XS in the US, do you know if they are available here in Europe?

Yes...

exclusive Commando parts | Holland Norton Works

www.hollandnortonworks.eu

kommando · Jan 17, 2021

fiatfan said:
That is from Mikes XS in the US, do you know if they are available here in Europe?

Go to ebay, then search in Motorcycle parts for 'EGR valve'

Example of new

Exhaust Emission Valve (EGR Valve) (EGR006) for Kinroad, Skyteam (#006) | eBay

Find many great new & used options and get the best deals for Exhaust Emission Valve (EGR Valve) (EGR006) for Kinroad, Skyteam (#006) at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

or select from 2nd hand ones and pick one to go mounted on a flange or to go in a pipe run to suit how you want to mount it.

B+Bogus · Jan 17, 2021

HanaAna said:
I'd say there is "lot" of room for bigger valves?

The external oil drain is certainly non-standard, but typical of a big valve conversion.
Standard valve sizes are 1.49" and 1.302" according to the data - worth checking yours.

The additional holes into the chamber I've never seen before - twin plug installation, perhaps?

A very interesting engine!