Combat Question

Alan L said:

God, but I wish I had of bought a JPN when they could be obtained for reasonable money. The sight of them still makes my blood stir. what a shame Norton didn’t put a bit more effort into the finish.
al

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They were ahead of their time, it was at least another 10 years until proper ‘racer replicas’ became mainstream.

Schwany said:

That dyno hill test is a good one, but kind of rough on an old Norton. I'd have to hit that in 3rd at around 70mph. 4th at under 50mph would not be a fun starting point with my motor. It would be on the verge of lugging with the immediate incline unless it was full of race gas. It weighs less than an 850 by quite a bit too. It would recover, but probably not well enough to get in the dyno hill record book.

Black caps I guess are the disc looking plate things Norton stuck in the ends of the exhaust. I never liked that look (too much like something BMW did, or would do) and put it out of my mind. A Commando needs peashooters to maintain its dignity.

I could lose about 9 lbs, but I might need a time machine to pull it off.

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“Black caps” is the nickname given to the large, heavy, quiet, restrictive silencers otherwise known as ‘annular discharge‘ silencers fitted to later Commandos and also T160s.

Just by way of balance, the NOC service notes state that the 'black cap': DOES NOT REDUCE THE POWER.. and those are their capitals, not mine...
They do, however, note that balanced pipes must be used in conjunction them, and put forward the plastic airbox as the culprit for performance restriction..
From Mick Duckworth's book: 'The resulting patented design cut noise to the require level while not stifling performance'
I do wonder if the internal construction of the 'original' is truly copied by today's replacements? And given their all metal construction, are any used originals still 'as bought?'
Perhaps the eventual buyer of the 'new' JPN will give it a good thrashing and give us his verdict

EstuaryBoy said:

Just by way of balance, the NOC service notes state that the 'black cap': DOES NOT REDUCE THE POWER.. and those are their capitals, not mine...
They do, however, note that balanced pipes must be used in conjunction them, and put forward the plastic airbox as the culprit for performance restriction..
From Mick Duckworth's book: 'The resulting patented design cut noise to the require level while not stifling performance'
I do wonder if the internal construction of the 'original' is truly copied by today's replacements? And given their all metal construction, are any used originals still 'as bought?'
Perhaps the eventual buyer of the 'new' JPN will give it a good thrashing and give us his verdict

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My bike has the balanced downpipes and black caps killed it, whatever the NOC notes or Mick Duckworth says .Strangely my mate fitted Norton black caps ( as opposed to T160 black caps) to his T160 and the bike is fine, now that's just weird.

EstuaryBoy said:

I do wonder if the internal construction of the 'original' is truly copied by today's replacements? And given their all metal construction, are any used originals still 'as bought?'

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Indeed, I’ve often wondered the same about various silencers.

My conclusion is that I’m pretty much 110% certain that anything that originally had internals that were clever / difficult / expensive to produce, that is now replicated in the Far East, most definitely WILL NOT be as per the original design.

Look at peashooters FFS… just about the most simple possible design, but getting them made ‘right’ requires effort, diligence, and cost. So what on earth is going on inside new repro black caps, ray guns, etc, etc is just anyone’s guess. I’d even bet you could buy the same brand, at different times, and still get a different construction !

EstuaryBoy said:

Just by way of balance, the NOC service notes state that the 'black cap': DOES NOT REDUCE THE POWER.. and those are their capitals, not mine...
They do, however, note that balanced pipes must be used in conjunction them, and put forward the plastic airbox as the culprit for performance restriction..
From Mick Duckworth's book: 'The resulting patented design cut noise to the require level while not stifling performance'
I do wonder if the internal construction of the 'original' is truly copied by today's replacements? And given their all metal construction, are any used originals still 'as bought?'
Perhaps the eventual buyer of the 'new' JPN will give it a good thrashing and give us his verdict

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It's annoying that sellers sell black caps advertised to fit commandos and tridents when originally they were different inside

EstuaryBoy said:

and put forward the plastic airbox as the culprit for performance restriction.

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My MK2a still has the black box air filter, it has peashooter silencers with unbalanced pipes and in this setup needed the main jets changed from the MK2a 230 to the MK1 peashooter 260 to get proper full throttle response. If the black box was the restriction then that change would not work. So they may have put that forward but my bike disputes their assertion .

Alan L said:

# All things equal, how would a good Combat stand up to a Honda 750/4 and then Kawasaki 900 on the quarter mile? I presume it would be a nose ahead of the Honda and a noticeably slower than the 900, would others agree?

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People like to compare 1/4 mile times but as I see it, Commandos were lousy drag racers, but excelled in the turns and could easily outdistance any of the Japanese bikes of the time due to the difference in handling rather than acceleration on a twisty road. I did not have a Combat back in the 70s but rather an 850 Mk2 and I rode with a bunch of guys who owned Yamahas, Hondas and Kawasakis. They liked to show off their straight line speed and close ratio gearboxes because whenever we went anywhere that had a lot of cornering involved I would end up sitting somewhere waiting for them. I suppose if I'd had a Combat the wait may have been longer. But I had to work at it to keep up with them off the line. (No I did not have a 19 tooth sprocket) Those early Kawasaki 2 stoke 750s where very fast off the line but frankly I thought they were awful to ride.

Alan L said:

God, but I wish I had of bought a JPN when they could be obtained for reasonable money. The sight of them still makes my blood stir. what a shame Norton didn’t put a bit more effort into the finish.
al

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But you need to wonder why most of them have only around 10,000 miles on them. Sure they are rare, but also other things.

rvich said:

People like to compare 1/4 mile times but as I see it, Commandos were lousy drag racers, but excelled in the turns and could easily outdistance any of the Japanese bikes of the time due to the difference in handling rather than acceleration on a twisty road. I did not have a Combat back in the 70s but rather an 850 Mk2 and I rode with a bunch of guys who owned Yamahas, Hondas and Kawasakis. They liked to show off their straight line speed and close ratio gearboxes because whenever we went anywhere that had a lot of cornering involved I would end up sitting somewhere waiting for them. I suppose if I'd had a Combat the wait may have been longer. But I had to work at it to keep up with them off the line. (No I did not have a 19 tooth sprocket) Those early Kawasaki 2 stoke 750s where very fast off the line but frankly I thought they were awful to ride.

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Above was not my experience with my first combat versus Kawasaki H1.
Norton quicker off the line. By the time the Kawasaki started to catch up the race was over. But that was 48 years ago. Pretty much any modern 750 will blow my socks off now.

ILLF8ED said:

Above was not my experience with my first combat versus Kawasaki H1.
Norton quicker off the line. By the time the Kawasaki started to catch up the race was over. But that was 48 years ago. Pretty much any modern 750 will blow my socks off now.

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I'm glad to hear it! Breathing in the two-stoke exhaust is over rated and that's taking into consideration that nobody likes it in the first place!

When I first got my Norton and for a few years after all my jap bike riding mates all they wanted to do is drag race me but I always said I have nothing to prove, I couldn't care less what top end speed or who was quicker in a drag race and I didn't brag when I beat them in the twisties or up in the ranges, well maybe a little rubbing lol and even after building my HOTROD Norton I still had nothing to prove to my mates, I built my Norton for myself and didn't careless in how it stood up to in a straight line drag race.
I still ride with a lot of these mates and a lot of the Honda 4s boys no longer ride because their wife's won't let them, sad really but they still brag about how good their Honda's were and of course I always say "well where are they now" mine is still going and even better now that what it use to be and I am still running the same motor from when I first built it just with different crank cases from original cases but the inturnals are all the same.

Deckard said:

I'm rebuilding the 750 and utilizing a Jim Comstock flowed head with a Webcam 312 grind with same compression ratio, so I expect I'll be feeling the Combat experience +1. I'll still use a 19T sprocket, I still want to feel the thrill of what the Norton acceleration is. Top end on the East Coast of the US is rarely experienced without ramifications

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You will like this. I rebuilt my 850 with a JC ported FA head, 1.5 mm oversize vv, 9.5:1 pistons and a 312a. Goes like stink and runs away over 4k.

Alan L said:

God, but I wish I had of bought a JPN when they could be obtained for reasonable money. The sight of them still makes my blood stir. what a shame Norton didn’t put a bit more effort into the finish.
al

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I remember a local guy selling one for £1000 quite a few years ago. It was like new, but as I'd just bought a Ducati (not so much a race replica as a road legal race bike) I didn't lose too much sleep by not buying it. The JPN was just a bog standard MkIIA under the fibreglass after all.
Now if they'd gone for a Combat spec motor it would have been far more appealing.
The Black Cap or 'Annular Discharge' silencer was developed by Manchester University (a fine establishment!) as a means of maintaining gas flow whilst improving silencing, and I believe that in itself it was fairly successful. As already said, the plastic airbox was the main source of strangulation. Removing the intake silencer rubbers apparently made a significant improvement.
I ran a MkIIA in this configuration (minus those rubbers), and although it did lose a bit of the instant punch on acceleration it was actually a more pleasant bike to ride, and still lugged along nicely enough at motorway speeds.