'72 going back together

motorson

motorson

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I blew a head gasket on my '72 Combat so I decided it was time to check and see if the mains had already been changed to super blends. They had not been changed. I shimmed the crank to .005 with the new super-blends and shimmed the cam as well. Here it is going together with new pistons as well.
'72 going back together


'72 going back together


'72 going back together


'72 going back together


'72 going back together


I also relocated the oil pickup in the crankcase to the rear.
Dan.
 
Looks like Commando jewelry to lock up from some of us. I gotta look up to and take encouragement form some one just starting with the head then just being curious digs in to main bearing, cool.

I blew a head gasket on my '72 Combat so I decided it was time to check and see if the mains had already been changed to super blends
Click to expand...

How about that, I too found non superblends in long run Combats which just adds to the superblend mystery claim that they are what saved our Combat cases and in turn Norton itself - a while longer.
 
actually, the non "superblend" bearings are just fine

the only problem arose when the crankshaft whipped under high rpm which caused the ends to dig into the bearings which shortened their lives

this was particularly easy to do on the Combat because it was fitted with the smaller 19 tooth sprocket and it really was only when riders routinely zipped the rpms up to the redline area

many Combat owners enjoyed normal stock main bearing life by not spending abnormal time at high rpms

Shortly after I took delivery of my Combat I swapped the 19 for a 21 sprocket and put over 15,000 trouble free miles on it before selling it to purchase a new 850 the next year
 
Gosh darn it the folks I've heard from a long time ago that had good reports on their original Combat bearing basically said they hardly ever keep rpm down and i know that was the history of my first Combat and suspect similar in the one from New Orleans army base. My 1st Combat was demo bike with a reputation before I got it and 3 others who got it to keep the reputation up till finally out horse powered including the son of original shop owner I got it from telling me he'd regular top it out about 120 which at the time amazed me wondering where in our twisted Oarks he could go that fast that quick. So maybe the foolish young hot rodders may of preserved them till we could superduper em, yet still better limit its red zone excursions.
 
I always wondered how many Combats snapped the crank compared to the amount that threw a rod due to oil starvation.
The traffic light grand prix selling pitch was fine as long as the next set of lights was on red, I guess :roll:

That Combat revviness is very addictive though. Good to see one getting some TLC.
 
I bought the whole bike on eBay from a guy in Virginia in 2005. It had less than 1300 miles on it but was a rusted hulk. I should have taken some pictures back then. I have Jim's reed valve breather on the back of the crankcase and it works great!
 
Is that PNG plate off the bike? If so, that would help explain why it was a rusted low mi. hulk.
 
Alert! Alert! Alert! Whose gonna tell what is so seriously wrong in this picture?

'72 going back together
 
RMA cam chain adjuster.... from experience here that I've read, it has a bad reputation.
Comoz (Jim Comstock) was offering a much better solution.

JD

hobot said:
Alert! Alert! Alert! Whose gonna tell what is so seriously wrong in this picture?

'72 going back together
Click to expand...
 
Bingo JD. If upgrading beyond a properly worn in factory tensioner for Jim's hydraulic version might also consider Andy the chainman version that don't stretch and slacken as much as stock cam chain.
 
Hey guys! I bought this tensioner before Jim came out with his. And, after about 2000 miles it shows almost zero wear. I think that throwing it on older worn sprockets would be a bad idea since they tend to wear oval due to the lopsided load of the cam shaft. But, this set of sprockets does not have a "tight" spot and she just glides along like butter. I will see if Jim is still supplying his unit when this one wears out. I also have a good Norton friend in the area who swears by the unit you see here. (He fixed your bike once - Hobot.)

Please also notice the high zoot adapter I engineered and had made for the Power Arc ignition. I have more of those for the better part of $100 each.

Dan.
 
Alrighty Dan appreciate your attitude and insights on the RMA tensioner which worked a treat on Ms Peel spanking sports bike by mid red zone WOT in 1st-2nd. Only let go on stuck throttle *well* past the red zone then it came apart and may be part of reason the oil pump snout got fractured through too though still ran pretty good up to 5000 rpm then power rise stopped. Rick of RMA told me Peel was the 1st ever to break it but I saw at least 2 other come-apart- reports here so hope your won't be another one. Peel had new vernier cam sprocket on new chain in case that matters but did fin the sprocket pin beat up till too loose in holes to trust so it get replaced by solid sprocket - once cam degree'd in by trial - error.
 
Hm, I try not to keep track or leave public record but $200-250 range but an old link groove worn factory tensioner works a treat in most famous powerful lasting Nortons so not really a performance improver but maintenance lowering by taking up chain wear slack so should hold a tune a bit better on the more valve control and mixture tune sensitive racers. On mostly stock engine I'd not bother but then again we only live once and if only main Commando to devote to > go for it and grin every time ya think about it as rest of engine does its blacksmithing thing.
 
I made a few tools to keep progress going:
Torque Wrench extensions in 12 point 3/8 and 7/16 for the CNW cylinder and head bolt kits.
'72 going back together


Side cover tool to stabilize the cam sprocket shaft while torqueing the cam sprocket nut:
'72 going back together


A poor man's way of holding the crankshaft while torqueing the oil pump drive nut and the cam nut:
'72 going back together
 
Along the way I relocated the oil pick up to the rear of the Combat block:
'72 going back together


'72 going back together


Also blocked off the "correct" holes for the timing side. (See Jim Comstock recommendations.)
'72 going back together


Had to fix a busted engine mount:
'72 going back together


Shortened the exhaust valves and installed lash caps to get the rocker to hit inside of the edge of the valve:
'72 going back together


'72 going back together


The intakes look about right without any changes:
'72 going back together


Dan.
 
With the valve covers sitting in place:
'72 going back together


I'm starting to get excited to ride!
Dan.
 
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