Hi all, I have to replace my 4S cam, what with though, STD or 4S?
The bike was built as a MH Replica PR with MH big valve head, 4S, 10-1 piston & Rita EI with 4S advance curve.
Now, it’s got FullAuto head, std pistons, 4S.
I’m quite happy with the cam, but not sure if std or PW3 would be better?
TIA
Paul
big subject
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Std cam
For your spec with a Fullauto and flat top pistons a standard type cam is an excellent choice for power, torque and fuel consumption. Broad power band using twin Premiers, K&N filter and Peashooters. Also works well with mildly tuned 850s.
My cam with a Fullauto head is the Web#312, modern alternative to the cheaper standard 06-1084 cam but slightly more lift and duration with quiet valve clearances of 0.006" inlet and exhaust. Recommended and bought in 2016 from Jim Comstock in the USA.
Drops straight in as per standard using the existing timing marks, no fiddling with cam timing required. Either cam would be a good choice.
As Jan suggests, been debated to death with many "pulls like a train /strongest Commando I ever rode /substantial torque" statements but dyno runs don't back these up. Some with special cams like PW3 are no better than standard but probably due to poor engine or carbs setup.
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Thanks, I've had a read up…
Thanks, I've had a read up from access.
Neill, it looks like even a std cam(Newmans) has 0.016" gaps, RGM supply the std cam & 4S.
What's your thoughts on the Rita with 4S advance curve with a std cam? To be honest, I don't think I'd probably notice a difference, I'm 72 so don't ride like I was 16 anymore!!
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Rita
Yes I noticed the valve clearances, no idea why they should be 0.016" standard is 0.006" inlets and 0.008" exhausts. Worth having a word with Newmans or RGM. The Web#312 specs are below to compare. It's a welded cam using an old cam supplied by the customer.
I use a Trispark, not familiar with Rita. May work as is but worth getting it running efficiently if possible, even a 72 year old needs to blow out the cobwebs at times.
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Considering the bike now has…
Considering the bike now has a FA head with std inlet valves the best cam choices would be 06.1084 and PW3. The reason being without the larger inlets it is not going to rev as high as a 750. It makes sense to utilise the torque and not try increase the HP from the 850 motor, you have less under the curve to play with, and you don't get something for nothing. For road the use the above cams are ideal, even the std cam can get the read wheel to break traction if used hard.
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this has been debated many times , including recently on accessnorton: I suggest reading that one.