Topic: CB750 cam: Small differences really do that much?

[PeWe]

I'm very eager to verify the differences of these cams.
At left: "Similar to the Mega Cycle 125-75 but with 3 more degrees of duration....."
My new cam for new thrills next time on the road again.

Right:  Action Fours SS-1     Lift 0.360    duration:270       
"Ok with stock valve springs, smooth and tractable as a stock machine. The cam for those who are worried about "hot" cams."
My experince of this cam is very good!
Perfect for a general upgrade and reliable engine.
I have done 4 tourings thru Europe with this one and did very well on Autobahn, very smooth French highways as well as very curvy roads in the Alps between Austria, former Jugoslavia, Italy and beautiful roads around Andorra between France and Spain.
The not hot cam has larger measurement across, but higher base circle. But the hotter cam at left does not look that hot when comparing them.

It would be nice to upgrade the frame with removable tubes over the engine so the head can be removed without taking out the entire engine. I saw a Cb750 bike used as classic racer of max 750cc with that, just cut the frame and weld extensions over the frame parts and bolt on/off, a litte bit more flex. Possible to have fun with different cams, different weeks...

[trueblue]

That isn't really a small step up from the original one, that cam will make a noticable difference.  You noticed that is has a smaller base circle diameter, this is so you can achieve higher lift and duration while keeping overall size of the cam not much bigger than stock.  But to answer your original question, yes small differences can make a noticable difference.

[dave500]

if you run a cam with more lift in an older engine it will move the valve further than it has been before,,this in itself is ok but you can disturb carbon,your also pushing pre worn valve stems in their guides to new levels,,again not a terrible thing however the valve guide seal will also get a bit more flex as the rocker will push slightly more sideways on the stem,souping up older engines often results in smokey ones,,your going to be wanting to explore higher revs aswell.

[PeWe]

...maybe I should do the frame job to be able to lift the head out without taking out the entire engine with all work that has to be done before that. The paint job on frame and crank will be damaged too as well as my spine

I'll might need to replace the guides or just have fun with different cams. I'll contact the guy that had that as a sparepart...Hopefully one leftover or do another one for me...

All exhaust valves are new, inlet rather fresh, less than 10.000 miles. New cam appr 1 mm higher lift.
EDIT: I'll polish the used inlet valve stems that will have contact with the guides.
EDIT again: Checked valve stems and they are all smooth, all the way

[dave500]

i always polish valve stems,the guides aswell,they dont need a course finish like bores,,they dont need trapped oil,the pressure and heat isnt there.