Combat engine or not

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1up3down said:
Hobot,

I do understand that you own a Combat and thus are proudly biased in your assumptions toward that model.


Regardless, facts can and do often get in the way and tend to refute such obvious bias.


For example, the fastest quarter mile time recorded by an accredited tester was 12.2 by a stock 850

also, the highest measured top speed was 114 again by an 850, versus an average 109 for Combats

for your information, the Combat typically has a lower top speed due to it having a 19 vs 21 sprocket

I did not make up these figures, they are from my book having all of the Commando road tests 69-76
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I don't believe a stock 850 could out accelerate a combat, especially not with a 21T (20T was standard USA).
Something sounds very wrong with that road test.
Do you BTW happen to have that seven bike comparison test of 72/73? I've lost mine sadly. But I seem to remember they got 12.7 with the combat. That's just one test of course, but an 850 against a combat?
I know where I'd put my money, I've had both.
 
1up3down said:
I can accept 1u/3d's references that an 850, IF in Combat Spec, [ie: stage one hop up not offered by factory?] can get a few 10ths ahead of Combat 750 bombs, which would just back up my opinion if it ain't a Combat its a Cream puff.
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fine, except that by "stock" I meant out of the box stock and not "hopped up" or "stage one"

and I have no doubt that IF the stock 850 was fitted with the same 19 tooth front, it would be even quicker
than the Combat, this is due to the 850 having more cc's and torque and so quicker off the line

there is nothing "cream puff" about 850s, I have owned Combats, standard 750s and 850s...and have taken
all of them to the local drag strip, their quarter miles are all within a half second of each other and depend more on the track surface, tires, ride weight and rider ability than most anything else

I weighed 135 pounds back then and the fastest quarter mile time was with my 73 850, stock except for swapping the 21 tooth for a 19, and that was at 13 flat, and I was far from highly experience dragster

in fact, the only substantial difference in quarter mile time was with my stock 75 Mark3, best I could get out of it was 15.3 and that no doubt due to it being the by far the heaviest Commando built along with the 21 tooth sprocket of course
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You didn't mention what sprocket was on the stock 850 reported to have recorded 12.2 quarter mile.
Purely off the top of my head, I seem to recall extra weight of a MkIII was/is around 45lbs (someone correct me).
I'm not a dragster, not even interested in acceleration figures, but would guess 45lbs would not add 3secs to the run.
I know that was you, and the other was he. But it must be the sprocket issue, not weight. Some would be weight of course, but I can't imagine 3 seconds. Maybe the other tester was a jockey?
 
hobot said:
Alrighty 1up/3dn i agree you are righter than me on performance similarity so we're just bickering within same close family. Norton did know how to press its luck making power and mostly got away with it. Still a bit of logic static to be bragging that the extra displacement 850 can only match the lessor Combat in get go but I've followed a pure stock E-Start heavy loaded 850 and made to work for it at his mostly sightseeing rates. Oh yeah, the 135 lb advantage is not lost on me you jockey! Rule of thumb is 7.5 lb less = 1 hp more of acceleration.

LAB Who knows what funny business Norton did - maybe starting up a new charge account at a case caster while using up parts left over from last supplier Norton $tiffed. I truly belive to save costs Norton used existing fork springs and used less metal in lenght of damper rod to get by. I don't know what the cost difference might of been in '72 to know how much influence on fellas looking at powerful sports cycles to swing head-heart back and forth betwix a silver barrel drum brake standard Commando vs a black barrel disc brake Combat Commando.
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Yes, in hindsight I could have bought a new 750 with a brake with similar (maybe even better) performance that didn't blow up, for less than I paid for my combat. But none of us knew that at the time. But we sure found out. I think the price difference might have been around $200, but it's a long time ago, and $200 was more than now, obviously.
 
If you fitted a stock combat cam into a stock 850 motor , would the bike be quicker than a stock Combat 750 if you didn't change the gearing ? I suggest it would be - for the first few minutes. I suggest that a Stock 850 fitted with a 6 speed CR TTI box would kill most Combat 750s. The 850 is a slightly different concept - the heavier pistons limit the usable rev range, so the motor must pull harder for the same result. Lowering the overall gearing does not necessarily mean faster acceleration, if you are not using all of the available torque.
 
All the Combats and 750's I've know of came to USA with 19T but that not necessarily best for 1/4 mile as can't stay in lower gear to as high a speed. Combat or '72's had 420 lb listed. i got past Peel down to about 350 lb and i weigh about 165 suited/booted. I suspect if standard 750s woke up so much near red line they'd of blown in red zone too. Down low throttle snap to 30-40's mph, I think 750 standards might have an edge on Combats going by the spunk my buddies '71 has. I like the right now 850 torque response on the two i've tired but just didn't keep similar pull long enough is all.
 
hobot said:
All the Combats and 750's I've know of came to USA with 19T but that not necessarily best for 1/4 mile as can't stay in lower gear to as high a speed. Combat or '72's had 420 lb listed. i got past Peel down to about 350 lb and i weigh about 165 suited/booted. I suspect if standard 750s woke up so much near red line they'd of blown in red zone too. Down low throttle snap to 30-40's mph, I think 750 standards might have an edge on Combats going by the spunk my buddies '71 has. I like the right now 850 torque response on the two i've tired but just didn't keep similar pull long enough is all.
Click to expand...

Yes all combats were 19T. Don't know what was on earlier 750's but presume the same. Top speed of 107mph at 7000rpm was easily exceeded but the result of doing such was not what you would call a good outcome, until superblend saved the day (but I know hobot you don't believe they existed).

Standard MkIII USA sprocket I understand to be 20T. I'm guessing 21T for Europe. They go up to 24T now but that would be too high for my use.
 
L.A.B. said:
phil yates said:
But I seem to remember they got 12.7 with the combat.
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12.896 The bike wasn't to full Combat spec..

http://www.kawtriple.com/mraxl/articles ... bikes1.htm (2 pages)
The Norton was supposed to have had a hot “Combat” cam in it, but our readings showed the magic stick to be a slightly worn SS cam instead.
Click to expand...
Click to expand...

Where do you get this stuff Les? That's like a road test of the road test. Fascinating stuff. I wish I'd never lost my original.
Come for coffee tomorrow, bring your library with you.
If you can't make it, just send library.

Phil
 
That Cycle seven super bike road test was the clincher for me to get the combat. I had the option, both standard and combat 750's being on sale at the time. Style wise, I wanted a fastback with fork gaiters as the cerianis didn't then suit the fastback to me. Also, the drum brake looked more traditional but I figured the disc brake would be the way of the future with "fierce" deceleration capability. It certainly was the way of the future, still sitting on my MkIII outside, forty years later. But stopping power even in 73 (bought mine in March that year) was not as good as my Dominator single leading shoe and feel was negligible.

But I loved my combat, until it exploded. Sort of lost enthusiasm for it after that.
 
phil yates said:
Standard MkIII USA sprocket I understand to be 20T. I'm guessing 21T for Europe. They go up to 24T now but that would be too high for my use.
Click to expand...


My 850 I had back in the late 70s had 22T.
Out in flat country, it could have gone bigger.
It would still pull away from near idle revs from a standstill, so wasn't hard to live with by any means.
 
Rohan said:
phil yates said:
Standard MkIII USA sprocket I understand to be 20T. I'm guessing 21T for Europe. They go up to 24T now but that would be too high for my use.
Click to expand...


My 850 I had back in the late 70s had 22T.
Out in flat country, it could have gone bigger.
It would still pull away from near idle revs from a standstill, so wasn't hard to live with by any means.
Click to expand...

What country are you in Rohan?
Was the sprocket the original fitted as you mentioned late 70's well beyond "normal" 850, as opposed to "exceptional" 850 :)
Well beyond both in fact.
It's not moving from idle that concerns me, I'm sure it does that okay. But from there to 7000rpm interests me more.
20T on a MkIII seems a good compromise, well for me. I do around town (well village I guess) and country riding. There is a set of lights right outside the pub. I could never face the boys again being blown off by any car. I have a Norton reputation to maintain
:)
 
1up3down said:
I believe the USA Mark3s were all fitted with 21 tooth sprockets as stock
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Could well be so 1up. I'm not a USAian and certainly never owned a MkIII back then.
But my 1975 parts manual says:
20T Std N. American
21T Available.

That's the only information I've got.

Phil
 
I bought my 850 Mk1 lightly used/abused in 1977.
About a mile from Moxan Rd. (who were gone by then ?).

The 1973 printed 750 and 850 printed NV Workshop Manual lists, Part A,
a table of gearbox sprockets and RPMs and Top Speeds.

19t @ 7000 rpm = 107
20t @ 7000 rpm = 113
21t @ 7000 rpm = 119
22t @ 7000 rpm = 124
23t @ 7000 rpm = 130

MPH, of course.
 
Rohan said:
I bought my 850 Mk1 lightly used/abused in 1977.
About a mile from Moxan Rd. (who were gone by then ?).

The 1973 printed 750 and 850 printed NV Workshop Manual lists, Part A,
a table of gearbox sprockets and RPMs and Top Speeds.

19t @ 7000 rpm = 107
20t @ 7000 rpm = 113
21t @ 7000 rpm = 119
22t @ 7000 rpm = 124
23t @ 7000 rpm = 130

MPH, of course.
Click to expand...

Yes Rohan
You and I talked about 25 Moxon Road before, I forgot that it was you. Moxon Rd I expect would have been a distant memory by 1977.
19T was my only sprocket info regarding top speed, and your info is bang on. I shouldn't say bang, that's what happened to mine when I went over 107mph on the speedo and only by 3mph, but I think the mains must have been heading that way anyway.

Phil
 
1up3down said:
Combats, it is my understanding that when the crankshaft turned at high rpm it also "whipped", which then caused the ends to rock in the bearings instead of turning true, the rocking motion would destroy the bearings

the "superblends" are better suited to cope with this rocking by having a slight taper so no digging in

the 19 tooth sprocket combined with the compression and cam encouraged higher rpm usage, boom
Click to expand...

All above true.
Also I understand, the stiffened crankcases actually worsened the problem by allowing no movement of the main bearings to help cope with crank shaft whip.
 
Phil now ya getting into the tricks old Norton drag races used and preferred thinner 750 cases to 850 and ran a ball bearing on the TS. Search up Captain Norton Notes for most a year daily reading to catch up on Norton hop up history before and after the superduperblend trend.
 
hobot said:
Phil now ya getting into the tricks old Norton drag races used and preferred thinner 750 cases to 850 and ran a ball bearing on the TS. Search up Captain Norton Notes for most a year daily reading to catch up on Norton hop up history before and after the superduperblend trend.
Click to expand...

My last combat built in 93, was hopped up with a 3S (is that right - was there such a thing?) and higher compression. But the stiffer crankcases were used I'm pretty sure. It's a while back now. But it went like a bat out of hell and was reliable and leaked no oil. Best built Commando I've had.

Phil
 
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