Combat question
- Thread starter Robb2014
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Look in this thread. Page one. There is a pic. It is adjacent to the center headsteady screw on top of the head.
rusty-gold-t15769.html#p193601
rusty-gold-t15769.html#p193601
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Robb2014 said:
Robb
You will find the C stamped in the middle of the head under the head steady plate. So this must be removed to see the stamping. Another tell tail sign is the gap between the fins where the head meets the barrels. On a standard 750 this should be even where the Combat because of the head being milled another 0.040" would appear tighter at the transition. Combats came with 932 Amals instead of the 930 for the standard 750.
Hope that helps.
Cheers,
CNN
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Hi, I am working on a 750 , had fitted a Norris RX and timed it yesterday (pretty close to specs at 103.5° LCA instead of 104°), and now wondering if I fit the combat head staight away and so letting the 10/1 ratio, or dropping a bit with a JS copper base gasket (0.020" thickness so going from 10/1 to 9.5/1) or going further down to 9/1 ?? , just because of poor gas here in my country ??
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Back then the case and stem tag #'s matched. But its Norton #'s keeping, so who really knows.
200976 First Combat Bomb Engine
211110 First Detuned non Combat Bomb
http://www.classicbike.biz/Norton/Maint ... umbers.htm
Combat had the low rear breather tube 2ndary oil return cases and a milled head for thinner fin gap at gasket and feel like any other spunky 750 until 3rd 2S cam piston kicks in a few 1000 rpm below 7000 and really hard to resits runing right past that as front lifts in 1st 2 gears and blows oil out every seam and pore just asking for more of it again and again....
A Commando is one of the hardest things to bring one's self to shut off...
or part with
[video]http://www.youtube.com/watch?v=98lW5qLxK6Q[/video]
They all sound bigger than they look but not Harely obnoxious, ahhhh
but watch out for this common public road hazard stopping ya often.
[video]http://www.youtube.com/watch?v=XWJopYkjcEQ[/video]
Me showing off in non cafe' stance I use fairly often off road but here to give a sense of what others hear as a Combat grunts by towards its 2S cam wake up in 4th. Only got into maybe 80's here, Trixie 2S don't really catch her breath until 90 mph with 19T sprocket then maturity must kick in or going 120 in seconds.
[video]http://www.youtube.com/watch?v=rXnq3jqikxc[/video]
200976 First Combat Bomb Engine
211110 First Detuned non Combat Bomb
http://www.classicbike.biz/Norton/Maint ... umbers.htm
Combat had the low rear breather tube 2ndary oil return cases and a milled head for thinner fin gap at gasket and feel like any other spunky 750 until 3rd 2S cam piston kicks in a few 1000 rpm below 7000 and really hard to resits runing right past that as front lifts in 1st 2 gears and blows oil out every seam and pore just asking for more of it again and again....
A Commando is one of the hardest things to bring one's self to shut off...
or part with
[video]http://www.youtube.com/watch?v=98lW5qLxK6Q[/video]
They all sound bigger than they look but not Harely obnoxious, ahhhh
but watch out for this common public road hazard stopping ya often.
[video]http://www.youtube.com/watch?v=XWJopYkjcEQ[/video]
Me showing off in non cafe' stance I use fairly often off road but here to give a sense of what others hear as a Combat grunts by towards its 2S cam wake up in 4th. Only got into maybe 80's here, Trixie 2S don't really catch her breath until 90 mph with 19T sprocket then maturity must kick in or going 120 in seconds.
[video]http://www.youtube.com/watch?v=rXnq3jqikxc[/video]
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L.A.B. said:
Technically it's true, the Combats did have the low breather tube. But so did all 1972 bikes.
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marinatlas said:
Update on my combat with Norris RX.....you may recall we've talked before. You will need the combat head to increase compression. I doubt with the amount of overlap (duration) the RX has a std head will work very well. Mine with the combat head has reduced the lower end torque a bit, but the high rpm power is very nice
Maybe the down side is it makes a lot more exhaust noice...again so nice. Timing is important for this cam so make sure it's openning and closing to Norris RX spec sheet.
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Ok LAB, all '72's had rump breather and not all '72 were Combats, so all Combats and some left over '73's have it and it sure does return more oil volume than the pump does till wet sump cleared. One would have to check CR PSI in the 180's+ or head for CHO or thin gasket gap and mic cam profile to verify its Combat spec to that extent.
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L.A.B. said:
If you were presented a bare engine and asked if it was a Combat (assuming no serial number or head stamp) the following things you would check:
Rear breather instead of camshaft breather
No large sump plug
32mm intake
This would put it in the 72-73 750 era.
Final confirmation would be CR and camshaft.
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swooshdave said:
No.
swooshdave said:
No.
swooshdave said:
No, as the presence of one or all doesn't conclusively identify an engine as being a Combat engine so anyone relying in those features would be in danger of misleading themselves.
swooshdave said:
Correct, which is all those three items would identify it as = a 750 engine from '72-'73.
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My March and July Combats all had
rear breather
IS tank and covers, first introduced on Combats, b/g trim, March issue
small mean buggered fall out prone sump plug
32 mm ports narrow gasket seam
black barrel the pistons stick up TDC proud of surface .050"
plain roller non superduper bearing in fine condition
RH disc brake, which I understand was a Combat only feature during their run but added to others soon after.
Ignition setting 28" or dangerous back fire kick off's w points or Boyer
always rising power curve getting rather steeper towards the end.
rear breather
IS tank and covers, first introduced on Combats, b/g trim, March issue
small mean buggered fall out prone sump plug
32 mm ports narrow gasket seam
black barrel the pistons stick up TDC proud of surface .050"
plain roller non superduper bearing in fine condition
RH disc brake, which I understand was a Combat only feature during their run but added to others soon after.
Ignition setting 28" or dangerous back fire kick off's w points or Boyer
always rising power curve getting rather steeper towards the end.
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hobot said:
Yes, exactly like any other 1972 (and '73) 750 model Commando would've had, so they are not actually "Combat" features anymore than the fact that a Combat engine had two pistons, a crankshaft and an oil pump. :wink:
hobot said:
Again, that isn't an exclusive Combat feature.
I have front disk brake, hot cam, 32mm carbs (for now anyways), high compression head (milled it myself and the one with the "C" stamping has been shelved), a low AND high breather and it's a 1972 or at least thats what the stamping on the cases would suggest.
Is it a Combat? No.
Let me ask that again. IS IT A COMBAT? You bet yer arse it is.
Is it a Combat? No.
Let me ask that again. IS IT A COMBAT? You bet yer arse it is.
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L.A.B. said:
Holy misquote. I said that you need to look at all of those features. Any one missing and no Combat. (Not counting replicas like Pissy's)
Dang LES, who peed in your tea this morning? :mrgreen:
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