Since I had all the work done on my engine over these last 10 years (358 kit, ported and polished heads, racing valve springs, electronic ignition etc etc, not to mention the 5-speed trans and Amal carbs), one of the things that my mechanic John has asked me about was an aftermarket camshaft (like a Megacycle, Joy etc). I looked at Megacycle's website, and in their PDF catalogue ( http://www.megacyclecams.com/catalog/ca ... imized.pdf , page 24) they do list four different types of camshafts. I guess if I were in fact to get one, it would likely be the milder version. I think I'd also have to send my camshafts off to them as the 'core'.
But, does even doing this modification even merit consideration? Right now I have the stock camshaft, have good midrange, the bike can hit 90mph+ with ease, and I get about 110 miles to reserve on a tank of gas. Bike runs great, and I'm very confident about its reliability and happy with the performance. So why would someone even consider an aftermarket camshaft? Any benefits? Any drawbacks? Am I missing out on something?
I'd be interested to know if anyone has gone the Megacycle/Joy/etc route and how it changed the character of their bike - good or bad.
Thanks!
To Camshaft or Not to Camshaft....
Vince
As you have done so much to your bike I don't think you are going to be discouraged from trying something. I would steer clear of the wild Megacycle Cams as they need the head re-working to allow clearance for the valves at high lift. As you already have the 350 kit in there you are probably getting more mid-range punch but you might try and get some advice from the vendor on what might work with the pipes and carbs you have fitted. If I were you I would get another camshaft on eBay and get that re-worked. That way you can return to where you are now without too much trouble. I have one half of a CYB cam and I'm going to get another half match to suit. I want to try in in a CYB race bike. This is the CYB cam compared with the most radical Megacycle cam. I believe that the CYB cam offers longer duration but no extra lift.. You can just see the shadow of the stock cam in the Megacycle image.... G
'60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160 '66 Matchless 350 '67 CL77 '67 S90 '77 CB400F
Please show the bottom profile as that is where the follower/cam make the duration change possible. ........lm
LM
I took those photos a couple of years ago. When I am back from my next trip I'll get the parts out and take some more pictures. G
'60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160 '66 Matchless 350 '67 CL77 '67 S90 '77 CB400F
Good deal.
Not everyone knows what happens to a stock cam to make it longer duration. .........lm
In basic terms, the opening and closing points of the intake and exhaust valves (the result of the intake and exhaust durations and their lobe separation angle) determines the basic RPM power range and idle quality. The valve lift will affect the amount of power within that range. For a broad power band and good tractability, it's tough to beat the stock CB77 cams, even with the 350 kit. Personally, I prefer lots of low-end and mid-range torque, as that's what makes these things pleasurable to ride. If you were to raise the compression ratio a point or two, you would want to use a camshaft the will close the intake valves later (adding duration, which will lower the cylinder pressure) to prevent detonation with today's gasoline, but that will raise the RPM range, and diminish the lower RPM power. You need to assess the realistic RPM range that you ride in, as the occasional blast above 9000 probably counts for less than 0.1% of your usage. In the Megacycle line, their 121-00 would be about it for street usage. Contact Jimmy at Megacycle for a good explanation of the characteristics of that grind. He will hardface weld the lobes to add the material needed for regrinding, and you should also have him weld and resurface a set of rockers for best compatibility, if you decide to go that direction. Regards, Chase
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