Dyno runs before and after engine mods

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In case anyone is interested, some details about the engine:

I milled 1mm off the head:




I was stingy and wanted to re-use the pistons as the barrels were re-bored not too long ago and looked perfect. Due to the milled head the valves came too close to the pistons. So I had to cut pockets into the pistons:




Regarding the work on the ports. I left the straight part of the port at 30mm. I removed some material of the guides (sides only) and the port around the guides. Nothing removed at the bottom of the port. The black sheet shows you the shape prior to any work.




I deepened the bowl a bit behind the guide:




Probably not too important for this discussion but I still had to do it. Just for fun....



 
Last edited:
Joachim said:
In case anyone is interested, some details about the engine:

I milled 1mm off the head:




I was stingy and wanted to re-use the pistons as the barrels were re-bored not too long ago and looked perfect. Due to the milled head the valves came too close to the pistons. So I had to cut pockets into the pistons:




Regarding the work on the ports. I left the straight part of the port at 30mm. I removed some material of the guides (sides only) and the port around the guides. Nothing removed at the bottom of the port. The black sheet shows you the shape prior to any work.




I deepened the bowl a bit behind the guide:




Probably not too important for this discussion but I still had to do it. Just for fun....



Click to expand...

Now I get it…

I‘ve said it before and I’ll say it again…

Blue ones are fastest !!
 
I’m thinking of painting my tank and side panels blue to go faster without
the expense of engine modification

Perhaps I’ll start a thread on which shade of blue is fastest and does metallic
metal flake improve the performance or not?

Has anyway done dyno testing or drag raced blue against other colours?
 
Well it’ll male a change to be debating RAL colour charts instead of dyno charts !
 
Most are unaware that, while blue Commandos may have marginally more top end power than other colours, they tend to lack the exceptional midrange power of Black or Green Commandos.

Glen
 
When I got my 1st Norton (Atlas) I was not impressed. Compared to my previous flat tracker BSA it was a dog. So I spent some time porting and and switching to 32mm carbs with longer manifolds and free flow exhaust. I was amazed at the improvement. With a 19 tooth sprocket I was getting 2nd gear wheelies. So I went racing and even with a stock cam I was competitive. It doesn't take much to turn your bike into a cafe racer - as long as you do it right. Stripped down slimline that got me into all this.
Dyno runs before and after engine mods
 
Joachim said:
I remembered there was another bike tested on the same Dyno:

www.accessnorton.com

Dyno run (2017)

Had the "Nortan 850" dyno'd last week with very interesting results. The engine is standard apart from a Fullauto Technologies head, a PW3 cam and a VM34 Mikuni. The rapid dip in the torque curve is interesting. The motor is very strong in the low end and mid range as you would imagine with 50...
www.accessnorton.com www.accessnorton.com

'The engine is standard apart from a Fullauto Technologies head, a PW3 cam and a VM34 Mikuni'
Makes me think what makes the difference. Twin carbs? Higher compression?
Click to expand...
My short stroke 750, with twin 34mm Mikunis, NRP twin pipe Exhaust, PW3, JSM Pistons and very long rods, about 10.5:1 compression and a standard, unmodified Fullauto head made 60rwhp on the dyno!

It will be very similar after current strip/check over/build, so why does that always cost me money!

I may be the only guy racing with a Fullauto who didn't go big valve!
 
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