camshaft nut torque

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How tight do you guys like to make the camshaft nut? Can't find a torque spec on it anywhere. I was thinking maybe 30 - 40 lb-ft?

Debby
 
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Deb,

There is no specified torque for the camshaft nut - none that I could find in any Commando shop manual. 30 ft-lbs torque should be ok.

Jason
 
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Debby, from Fred at OldBrits site:"Camshaft sprocket nut (06-7774) 60 to 80 ft lb depending on cam metal".
Mike
 
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The Norton factory manual for 1970 gives the torque specifications of the rotor nut and the clutch to mainshaft nut as being 80 ft lbs and 70 ft lbs respectively, Since both of these nuts are of a smaller diameter than the camshaft nut (although of a greater thickness and therefore deeper thread engagement) I would have thought that 70 to 80 ft lbs would be within the correct range. I normally do the nut up as tight as I can with a bar and socket.
 
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If I remember right 70 to 80 pounds was about right, but years ago I was surprised to see Fred Barlow, ex norton development engineer using Loctite on these, he said he did this as a precaution.
 
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nut torque

Hello all, The main worry I had when doing this nut up was to try not to exert too much force on the idler pinion, as the out board section normally located in the outer timing cover. I must confess I used a rattle gun on this particular nut, in an atempt not to load up the idler.

Cheers Richard
 
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I thought I'd split the difference and run it down to 50 ft-lbs or so. Average out all the responses! :p

I haven't torqued it down for good yet though. Might need to take the sprocket back off to install a shim or two. Cam has a lot of endplay, which may or may not be a problem. See separate post about that...

BTW the factory manual sez NOT to use an air gun on the nut. I think their concern was the intermediate spindle (if I read it correctly)...

Debby
 
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Can't give a specific figure but it really doesn't need to be tight at all. For a while I had a PW3 cam on my Commando which is made of cast iron and very brittle and I was warned by Norman White not to tighten it much more than nip it up otherwise it would break. I probably had it at about 15 lb/ft and it never fell off. Obviously you don't have that worry of breaking your cam but I wouldn't feel the need for leaning heavily on the end of a long spanner, would think 30lb/ft would be plenty.
Regards
Snakehips
 
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Snakes right, if 15 works on a cast iron then 30 will work fine on steel, use loctitie for extra insurance and a cut-down timing cover for supporting the intermediate shaft.
 
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yes as Kommando says you do really need a cutdown cover when doing this especially if you are leaning heavily on a spanner on the nut otherwise you risk putting a lot of stress on the idler shaft and once the shaft is loose in the crankase the only succesful cure is to copper plate the end of the spindle where it engages in the case. I had no joy at all with loctite and everytime I took the timing cover off the spindle had spun. Couple of thou of copper plating fixed it for good. Its also a lot harder to set the cam chain adjustment accurately without a cutaway cover on there.
Regards
Snakehips
 
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Commando servicing notes say dont torque up camshaft nut without suppoeting outer end of idler shaft, ideal is a scrap cutaway timing cover, but any method of supporting shaft such as an accurately drilled plate bolted to crankcase
 
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Just rebuilt my motor for the third time - long story, broken ring and knackered exhaust seats! Always do the cam nut up to 25ft/lbs and have never had one come loose. i always meant to make a support for the idler shaft but if you apply steady torque to the nut and don't snatch at it it should be OK, not ideal I know but it works.
I have a Q for Snakehips? You said you once had a PW3 in your engine....any reason for removing it? I was thinking about one but the extreme lift on both I & E made me think it would be a bad idea. 10,000 miles ago I replaced the Combat cam with a stock item hoping to get a lot more bottom end but it didn't make much difference and I lost the top end rush of course so thoughts turned back to a hotter cam. My head has been worked over and has big ports with 32mm carbs so I probably shouldn't expect loads of low speed torque like a stock 850 say. Would be interested in why you changed.
 
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Good question keith, I think I must like taking my commando motor apart. There were two reasons really the first may sound a bit daft but it didn't really sound like a commando anymore. Like you I have bigger ports 32mm carbs and black diamond valves and it was really blatty with the PW3 sounded good but not like a commando. Other reason I knew I would probably blow it up big time as it really breathed well and on several occasions had it well over 7,000 rpm and it kept wanting more and as it has standard crank rods cases etc I felt I was courting disaster. Still sounds sharper than your average commando with its standard cam I guess thats down to the head. Nice cam the PW3 but if you fit one you will have to open the cam tunnel out a bit to clear its big lobes and also make sure it clears the lifter tunnels ok, also check for coil bind on full lift, you will probably have to remove the heat insulators under the valve springs. Other thing that always worried me a bit was that I have 20 thou oversize exhaust valves and when the inlet and exhaust valves were on the rock passing each other you could just about get a fag paper between them (well a little bit more but not much) and I was a bit concerned they might get tangled up with each other on a missed gear. Other minor niggle is PW3 runs 11 thou clearances inlet and exhaust so does sound a little more rattley.
So those were the main reasons but I think the best solution would have been to buy another commando and have one with the PW3 etc and the other stock :)
Regards
Snakehips
 
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Snakehips, that's kind of what I thought you'd say and after already blowing my old Combat motor 3-1/2 yrs ago which wrecked the cases, one rod, Maney ally barrels and both No 1 valves I don't want to go through that again. It even bent the LH frame rail and it took me a while to figure after the rebuild with good 850 cases why the front ISO bolt had to be forced into place...it was over 1/4" out. That made it vibrate like hell. They are Commandos after all so unless we've got 000's to spend on HD cases, crank and rods and 1000cc conversions we just need to accept their limitations ! Cheers.
 
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