camshafts for 750 Commando

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Looks like our moderator removed the timing specs. The Norris D spec is
intake open 53 degrees BTDC close 83 degrees ABDC
exhaust open 83 degrees BBDC close 53 degrees ATDC

Would thinkg the RX grind is the same just lower lift...can you confirm?

Thanks
 
URL to swell up as desired. Norris D
http://rides.webshots.com/photo/2841736 ... 1179GJDEZH

camshafts for 750 Commando
 
beng said:
Some of the literature supplied with the Norris Rx cam and springs:

Many thanks...just what I was looking for. 54/82 degrees is what I measured after installing this camshaft. Looks like it's good to go. The valve springs are per combat spec, so should be good for this camshaft as well. The double S cam has more lift at intake than the Norris RX.
Click to expand...
 
I'm not an expert (or even competent!), so please confirm for me that there's something wrong with spec sheet (below). The end of the red "exhaust" line should overlap the beginning of the blue "intake" line. As it is the overlap written on the sheet is incorrect at 166 deg, it should be 106 deg. See the similar sheet posted by Beng, above.

hobot said:
URL to swell up as desired. Norris D
http://rides.webshots.com/photo/2841736 ... 1179GJDEZH

camshafts for 750 Commando
Click to expand...
 
hi There, here are the Norris RX timing:
exhaust open 82 BBDC, close 54 ATDC
inlet open 54 BTDC , close 82 ABDC
duration 316 both ,all those figures are taken at 0.20"
lift exh and intake 424 at cam

for the R grind:
exh: 83 and 53
inlet: 53 and 83
lift 404 , both.
hope this help.
 
The key word is "need". Maybe we should use the word "should" instead. If all the parts were new you could swap them around at will. Used components should be reground to square again. A lot of worn cams display wear more to one side than the other. It is important to always return each lifter to it's original tunnel on reassembly. Think of the tunnel geometry as the 3rd. part of the "lifter - cam lobe set". If there is not significant wear on your cam or present lifters and all you want to do is try the cam you won't do much damage running it for 50 to 100 miles to determine that this is the cam for you. If you already know you definitely want to get rid of the stock cam and we wouldn't hold that against you, then maybe grind your current lifters with the new cam. It sounds like this cam may require stronger springs which is another case for the resurface.[/quote]

OK as soon as I can find a place that can re surface the lifters will get that done. Not sure about the springs. It has the combat specs already. Just measured the total unsprung length of the outer intake spring and it's right at 1.62" per the service manual spec. Will check with Ken Armann to see what he recommends. ken's our 2012 club president, so will get plenty of talk time with him next year (I'm the VP....again).

Thanks
 
I was just looking at the lift on the 1st chart for the RX. Ooops, I just noticed the chart shows lift at the valve (when I started this post I was thinking it was at the cam) so I started making the comparison below because it was significantly different from the combat. However once you compute the rocker arm ratio into the equation they aren't that far apart. I'll post it anyway.

----COMBAT @ cam------COMBAT x 1.13 (@ Valve) ---------NORRIS RX (@ valve)

IN.________.390"__________________.441"__________________.424" (.017" less than combat)

EX.________.346"__________________.391"__________________.425" (.034" more than combat and I think quite a bit more than a stock 850)

So it looks like the ex valve to piston clearance must be checked with this cam as it may need some pockets cut into the pistons. I don't remember what the recommended minimum clearance is, .050" comes to mind but it's been too long since I've meddled with this stuff and perhaps someone else can chime in.

Ex valve springs wear more from the heat but intake valves weigh more so they all get taxed in some way. You could lighten the rockers to help prevent valve float. Even just doing the ends and you could also look for the light alloy adjuster nuts to help cope with the extra load on the exhaust springs.
 
Hi, I am new to this forum. I do have a number of brand new Norton performance parts by Norris if anyone is interested. Three pieces of RX cams, valve springs, bronze valve guides, quick change cam bearings, copper head gaskets and more. I am located in Sweden.

Ake
 
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