Hello,The reason I bought the head was to replace mine if the valve guides get worn out like David C's did. David managed to get replacement guides somehow though so I would only be down for shorter while in that case. I don't like being down especially with this bike.
Well, on the positive side, plenty of room for improvement.A new head is not much better tha your old one. The seats are not 100% ok and the valve guards are to wide dor the valves. The seals are complete shit.
Talk to Ollie Thiel at Thiel Mortorsport in Germany, or if he doesn’t respond, talk to Panetone (above) and ask him to talk to Ollie !Got this response back today. When the time nears and if nobody is willing to send in a cylinder head, I’ll probably purchase a new one. At least there might be hope for power gains. Who would be a candidate to grind custom cams for the 961?
Worth doing everything, upgrade wise, to the new head before fitting? Probably already in hand!OK , Thanks for checking. I will have a head , either a this new head or my removed original head after I install the new one.
OK , Thanks for checking. I will have a head , either a this new head or my removed original head after I install the new one.Got this response back today. When the time nears and if nobody is willing to send in a cylinder head, I’ll probably purchase a new one. At least there might be hope for power gains. Who would be a candidate to grind custom cams for the 961?
I am pretty happy right now , these cylinders and pistons measure right in service manual specs . I just got the head back from the machine shop and guides and stems are perfect .In the latest Email from AF1
"Norton News: We are happy to report our first Norton spares order has been received!
Norton is officially back in business!!!
It'll be a long while before we see bikes imported to the US again, but we can support the existing owners with spare parts!"
AF1 Racing. Norton Motorcycles - Spare Parts
www.af1racing.com
Are the piston rings gapless or file fit?I am pretty happy right now , these cylinders and pistons measure right in service manual specs . I just got the head back from the machine shop and guides and stems are perfect .
The valve lifter bores are mirror polished. I am including this because someone asked what the lifter keeper bolts were. You can see them at the bottom of the lifter bores , they stop the lifter from rotating in their bores .
Cross hatch honing from Norton UK
With a valve job from a trusted machine shop.
Finally , A proper top end .
Not gapless rings. Norton OEM rings. Not CC’d. As they came from Norton .Are the piston rings gapless or file fit?
Are the chambers CC measured by any chance?
Is there a reason you’re replacing the cylinders, pistons, head etc?Not gapless rings. Norton OEM rings. Not CC’d. As they came from Norton .
Hello Voodoo , This was done to get to the bottom of my oil in air box issue . Lets use the 1oz. (30ml) per 1000 miles of riding as a minimum goal , and I will hope for better and I think that is achievable . My last test showed ~ (15 ml) in 300 miles at best . That is at a relatively steady 70 mph. As far as performance increase , if I get any I will take it .Is there a reason you’re replacing the cylinders, pistons, head etc?
Are you doing it for a rebuild and no performance gains?
Hello FE , These are not high compression pistons , only what Norton UK supply me as OEM . Looking at Ollie Thiel's pistons , with no dish and what appear to be deeper valve pockets. Those would probably increase the CR hey ? Now that I have my cylinder bore measurment , I could email Ollie and discuss it suppose . I was worried about having the right setup for Nikasil cylinders .Those parts all looks really nice. No signs of porosity etc, nice machining. Good to see.
I like the proper squish design of the bathtub combustion chamber. But I notice the step around the outside of the piston crown. That’s strange, it means that even if that step is gapped properly to the head to get a good squish, the rest of that squish area on the head is wasted. Ideally any recess in the piston should match the bathtub shape. Even more ideally, no recess is needed!
I’d look into what the CR would be with a flat top piston and a 0.040” gap. If you assume 1mm it makes it very easy to calculated the volume of that squish gap to add to the measured CCV to calculate CR.
As I’ve discovered on my 920 engine, a working squish allows a surprisingly high CR without issues. But you boys in the US who take long trips do have to factor in using low octane fuel when needed.