jseng1 said:
Robert
Maybe it was not your intention to spread bad news about the PW3 cam ...
Jim (jseng1),
Not trying to spread bad news about anything, just trying to make sure Peter R doesn't make a decision without having all the information available to make the best one for him. The videos are informative and straight to the point. However, for all I know -- which isn't much! -- you can tinker with other variables (springs, rocker arms, and who knows what else?), to reduce the bouncing.
If Jim Comstock is going to go to the trouble of helping the collective by posting online videos showing the results of his testing, the least the rest of us can do is share it with others who may benefit from our doing so.
Jim also posted some JS2 cam results, which I have not watched, but I saw the titles listed while viewing the titles of the uploads in his youtube channel.
What I'd really like to know is how much a stock cam bounces when wound up to 7000 RPM -- when set up optimally.
There are a couple of Webcam grinds, 12 and 12A, that Jim Comstock discussed here, in this thread:
cams-t12813.html . If those cams performed well in the Spintron testing, they would be what I'd be looking at, and probably the plain 12 and not the 12A.
How much does lightening the rocker arms help to prevent bouncing? If at all?
I had a D+ Norris cam in a bike years ago, and could never get the thing to run right. Wouldn't pull past about 6000 RPM's. I'd probably be dead now if it had, but it was a very disappointing and frustrating experience. One lobe was completely gone at 5000 miles after the rebuild. At the time, when I was trying to get it to run correctly, I considered lack of fuel, air, wrong mixture, and maybe considered the timing. Never thought about the compression, or that it might have been a head flow problem.
The fastest two Nortons I've ever ridden both had stock cams. Bike #1 was a 1970 Roadster, with a 19 tooth countershaft sprocket, and a single Mikuni. Don't know what intake manifold it had, although I don't think it was anything special. That bike had no problem pulling redline in 4th gear, which was an indicated 105mph. Very quick, too. The only area where a 19 tooth sprocket falls short is the increased revs at freeway cruising speeds. I think that bike had a Boyer in it. It belonged to a friend of mine. My brother had a MKIII with a single Mikuni, and that bike wouldn't go much faster than about 90. Was fine up to that speed, though.
Bike #2 was a low mileage 74 850, with a fresh valve job on a stock RH10 head (maybe milled 10 thousandths), sleeved Amal carburetors, Boyer ignition, 20 tooth countershaft sprocket, and 27 inch Dunstalls that had had all the internals removed. I wound that bike up to 7000 RPM in 4th gear just once, which it did surprisingly easy, resulting in 110 MPH being indicated on the speedo. The bike felt dangerously light at that speed, so I never attempted to ride it that fast again. There was no fairing on the bike, and it had euro style handlebars.
Here's a couple of links to a youtube video showing the bike with the D+ Norris cam in action vs. the 1970 Roadster mentioned above:
https://www.youtube.com/watch?v=Hr4rMneeR1Q
https://www.youtube.com/watch?v=lFTgeRNzUdc
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