Recommendations for a 850 MK IIIstock cam replacement

Looking to replace the failed cam in my MK III. Want to keep the low to mid range torque the original cam provided but do not know which manufacture currently has a good track record for a durable Norton cam. Have a pretty good looking core that could be built up and reground if that is a good option.

T W Hudson

WebCam 312. Good low and midrange with a better top end.

1. Greg Marsh right here on the website has stock Andover Norton parts. https://gregmarsh.com/MC/Index.aspx
2. Web Cam can weld up your stock cam... https://webcamshafts.com/pages_vehicles/motorcycle/norton/1777.html
3. Jim Schmidt has JS0, just a little more agressive. https://jsmotorsport.com/camshafts/
4. Looks like Andover Norton is out https://andover-norton.co.uk/en/shop-details-2/15520/camshaft-standard-with-lube-pack

Right now, I have one each, standard, 2S, and 4S by Hepolite. For standard compression I don't recommend 2S (the Combat cam). If just doing normal street riding, then I recommend the standard cam. If you want a little more performance, you could consider the 4S but it really depends on your riding style.

I'm out of AN cams because AN is out of stock. When I do have them, they cost about 2-1/2 times more than the Hepolite cams.

I would look at the JSMotorsport 0 cam any more duration than that and you will start to lose bottom end in exchange for top end. The JS0 and the web cam 312 are very similar, and are probably both based off the BSA A65 cam. The benefit of the JS Zero is the asymetrical lobes, and using lighter lifters (you can also get your stock lifters re-rediused by JS).

maaseyracer said:

I would look at the JSMotorsport 0 cam any more duration than that and you will start to lose bottom end in exchange for top end. The JS0 and the web cam 312 are very similar, and are probably both based off the BSA A65 cam. The benefit of the JS Zero is the asymetrical lobes, and using lighter lifters (you can also get your stock lifters re-rediused by JS).

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Appreciate the input from everyone!

The normal cam which is used in the 850 is a hot grind in relative terms. When everything is adjusted to suit it, a Commando should be fast enough for anyone. The main thing which causes a Commando to be a bit slow is probably the gearbox. If you want a fast bike, you need two things - the gearbox and the front brake. The Japanese are not stupid.

Always wished the 850 had the brakes and a 5 spd. transmission like my '78 900SS Ducati has. I am going to check deeper into the Webb 312 cam. I have a pretty good core that I am pretty sure could be cut down, hardfaced and reground. The normal 850 has plenty of power for me for sane highway riding better brakes and another gear ratio between 3rd and 4th would allow brisker riddin on the type roads we have in my area.

One of my friends said - 'if you have a torquey motor, you do not need a close ratio gearbox'. His opinion was probably based upon supposition. When I first raced my Seeley 850, the gearbox was the first thing I changed. When you ride a bike with a Commando engine, it is easy to believe the bike is going as fast as it can, because of the deception caused by the heavy crank. With the wide ratio box, my bike was useless. With close ratios, it is much faster everywhere. When you lose revs on up-changes, you become dependent on throttle response. You tend to wind on too much throttle and the mixture richens quicker, so the bike is slower. However when the heavy crank is spinning high, nothing stops it - particularly when you race-change up through the box. The crank inertia becomes an advantage. Leaner needles might be good in a road-going Commando.
I have come to believe the Commando 850 motor is an excellent design.

Whenever a Japanese manufacturer brought out a different model in the 1970s, the needles and needle jets in the carbs, were always different. I wonder if Combat 750 Commandos and later models have different port sizes but similar needles and needle jets ? If you used a Commando for commuting, you might not notice the difference.