Mark 3 verses the rest

MichaelB said:

Interestiing Read..

Geoffrey Roe: The Annular Discharge Silencer

The following blog hopefully gives an insight into the research and development work carried out in the early 1970’s into the efficient...

yorkshireferret.blogspot.com

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I wonder and hope the black caps that are being made presently have the same internals as the originals on the OEM bikes. I know parts of my OEM black caps have internals that are rusted out. I do have a set I got from RGM and will install them and see if they "feel" ok Power wise and sound like they should. I'll do a back to back test this week.

Carl H said:

I wonder and hope the black caps that are being made presently have the same internals as the originals on the OEM bikes. I know parts of my OEM black caps have internals that are rusted out. I do have a set I got from RGM and will install them and see if they "feel" ok Power wise and sound like they should. I'll do a back to back test this week.

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Please let us know the results I fitted RGM black caps eleven years ago, but just this month swapped them side to side as one was starting to show pits in the chrome along the top of the silencer. T'other side and both underneath still fine, though.
I prefer a quiet bike, but they do have a satisfying bellow when you wind on

Carl H said:

I wonder and hope the black caps that are being made presently have the same internals as the originals on the OEM bikes. I know parts of my OEM black caps have internals that are rusted out. I do have a set I got from RGM and will install them and see if they "feel" ok Power wise and sound like they should. I'll do a back to back test this week.

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That is the question.

Factories may have invested heavily in R&D on optimised internals. But I’d struggle to believe your average sweatshop in Taiwan knows or cares about that!

Maybe the quality ones are faithful and accurate reproductions? But I’d bet my bottom dollar that your average auto jumble / eBay offerings are most certainly not !

Fast Eddie said:

That is the question.

Factories may have invested heavily in R&D on optimised internals. But I’d struggle to believe your average sweatshop in Taiwan knows or cares about that!

Maybe the quality ones are faithful and accurate reproductions? But I’d bet my bottom dollar that your average auto jumble / eBay offerings are most certainly not !

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As an aside... There was/is a guy with a couple of aftermarket black caps for sale on ebay, but he wants you to buy one then 'negotiate' a price for the second...
Too much faffing about for my liking...
Hopefully AN will chime in with the authenticity of their offerings?

EstuaryBoy said:

As an aside... There was/is a guy with a couple of aftermarket black caps for sale on ebay, but he wants you to buy one then 'negotiate' a price for the second...
Too much faffing about for my liking...
Hopefully AN will chime in with the authenticity of their offerings?

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You often see black caps for sale to fit a commando or a t160 trident !!
The internals are different!!
Something I didn't know until relatively recently when LAB pointed it out
These people selling would not care what they are selling as long as you buy them

baz said:

You often see black caps for sale to fit a commando or a t160 trident !!
The internals are different!!
Something I didn't know until relatively recently when LAB pointed it out
These people selling would not care what they are selling as long as you buy them

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Out of interest is there any way to tell them apart?

My original Commando ('71) had the 19t sprocket. The 73 I bought in '06 had a (PO-installed?) 23T. I changed to a 20t when I converted to a CNW 520 chain but I often wish I had duplicated that 750's 19T! I like the 19's performance acceleration-wise. Whether the bike can only manage 105MPH on the top end as opposed to 120MPH is not particularly useful to me in riding on current, congested roads. In the twisties, again, to me the acceleration is worth more than top speed I can't use.

As far as comparing 'seat of the pants' for the different year Nortons, I agree that IF they all had the same gear ratio and all running correctly, it would probably be impossible to feel any difference.

cliffa said:

Out of interest is there any way to tell them apart?

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The Norton type have a rivet in the centre of the black cap

The 850s do have more grunt than 750s in the mountains.
The dyno tests Ive seen generally show that extra low and midrange poke.
At high rpm they are very close for output. I guess that is why in period drag race tests (before black caps) the 750 and 850 results were similar.


Glen

Don't believe any of this. Form your own opinion by riding different models. People favor whatever they own and whatever mods they chose to make.
(Everyone knows that all 850s are slow heavy pigs.)

baz said:

The Norton type have a rivet in the centre of the black cap

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Later, they were etched with the part number (06-4170 for Norton) and patent information.

Carl H said:

Big Red my 1975 MK2a with an RH10 ( that is the year the factory paper work said) Could do 100 MPH in the quarter and that is what the speedo read at the stripe, so the Smith gauge was accurate. I had it red lined lined at 7000 on Rt 140 reading 120 MPH a few times. One thing I was good at was a very tight tuck and getting under the wind. Big Red was a real "Road Runner"
Remember The S models were probably the fastest of the 750s Commandos and they has a 28MM port. I think the Combat is not the greatest due to the Cam and the cam timing, I had to advanced my recent reworked Combat 5 degrees to get it near the OEM spec. I think the Combat head it self is a decent port. But I 'd have to drag race them to get a better handle what they do.

Right now my MK3 , Now with a WEB 12 Cam and an RH10 that was on my Maximum Overdrive " Atlas "race bike is scary fast to me, and both the MK3 and Combat haven't seen 7000 yet as I'm breaking them in and I'm limited on the rural roads I'm on, and I'm leery of tearing up the trans gears and speeding tickets and the idiots on the roads. But I can feel them getting faster as they loosen up and the parts are getting used to each other and they get dialed in.

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A correction of " scary fast" I did not ride bikes for about 10 years, so when I got the MK3 running again, and saw the cam was junk. I did the recent rehab, I had not remembered the 22 tooth sprocket until I saw it when it all came apart. Muscle memory is a good thing, but now with a fresh hopped up engine and a 20 tooth, and since I have not had a fresh engine since I did the last race bikes in 1989. The first time I gave the MK3 a wack of throttle, It reved so fast it startled me , I did hit second ok , but by the time I chopped the throttle, , The front wheel was off the ground. So I said to my self, "I pity this poor transmission." The second time As I was leaving an old friend after talking about bikes we owned, I figured I'd show him what I was talking about and rolled out into the street very slowly , squared the MK3 up and was at about 1000 RPMs, I gave her about 3/4 turn of the twist grip and red lined 3 gears Real quick. I always geared my bikes tall and my memory is expecting a little more time to get settled and into shifting gears.

Today I pulled the top end of my second race bike built in 1989 and saw the gearing , Daytona type equal to over a 22 tooth sprocket. I don't remember if it has a close ratio 4 speed, But it was not ideal gearing for the Loudon track , but still delivered some big wins there and at Laconia.. On the street there were times when the tall gearing was real good, A few times I had flashing blue lights coming after me and There was no stopping Big Red and the chase was on. I'm 3 for 3 on that one, I just had to lay low for a few days and act innocent after, but they knew who the culprit was, and told me so later.

MKIII improvements in my book are improved head steady, stiffer swing arm, easier to use handlebar swiches, adjustable ISO's (nice to have but not a must have) . Kickstart arm that doesn't hit the mufflers.
Things I don't like are sloppy shifting (very vauge and cross over shaft splines wear quickly). World's ugliest air box. Much more complicated wiring and those little multi pin plugs that easily corrode, headlight stuffed with wiring. Starter that doesn't unless upraded. Fragile starter clutch. Horrendous noise from primary when starting. Seat hinge breaks. Ugly black cap mufflers. Rear disk locks up too easily.

And all Commando's need the 13mm master (front only).

Give me a '73 or '74 850 with a 200 watt stator and an Alton starter
kit anyday. Why Alton? You can keep your "ham can" air box and it comes with a higher output alternator at lower revs.

I have a nice MKIII for sale right now. Check Robbins Classic Motorcycles for more info.
https://robinsclassicmotorcycles.com

Carl H said:

I love all my Nortons, But the MK3 became my ride of choice due to the E start and quiet pipes and low induction noise, Once sorted out , It was great. Now with a WEB cam and a ex race bike head. it is quite fast and still with OEM black caps. People enjoy seeing and not getting their ear drums blown out, They actually smile and wave as I purr by. And I can ride it in and enjoy it . The rack makes it a real grocery getter and I have carried many heavy loads.



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I have never met a person who did not like the sound of the peashooter mufflers, not 1.

Interesting list of MK3 problems Charles. I've owned mine for 18 years now and have encountered the starter sprag problem on your list, but that is it.
The rear brake has always been perfect.
The front brake wasnt up to the job so I replaced it with a Madass. That handles all the speed I can throw at it.
To my surprise, the original multipin connector still works to run my heated vest. That's quite amazing after 46 years!
Seat hinge is also 46 years old and not broken. Perhaps yours saw some abuse at some point?

Glen

Charles Waggett said:

I have never met a person who did not like the sound of the peashooter mufflers, not 1.

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Put me in the not 1 list.

Charles Waggett said:

MKIII improvements in my book are improved head steady, stiffer swing arm, easier to use handlebar swiches, adjustable ISO's (nice to have but not a must have) . Kickstart arm that doesn't hit the mufflers.
Things I don't like are sloppy shifting (very vauge and cross over shaft splines wear quickly). World's ugliest air box. Much more complicated wiring and those little multi pin plugs that easily corrode, headlight stuffed with wiring. Starter that doesn't unless upraded. Fragile starter clutch. Horrendous noise from primary when starting. Seat hinge breaks. Ugly black cap mufflers. Rear disk locks up too easily.

And all Commando's need the 13mm master (front only).

Give me a '73 or '74 850 with a 200 watt stator and an Alton starter
kit anyday. Why Alton? You can keep your "ham can" air box and it comes with a higher output alternator at lower revs.

I have a nice MKIII for sale right now. Check Robbins Classic Motorcycles for more info.
https://robinsclassicmotorcycles.com

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With the CNW starter in my Combat, I do miss the ham can, but with the OEM charging system I have no trouble charging and the MK3 Yuasa YTX battery that is quite old , and is working well. I'm quite sure a good, new 10 or 12 amp battery would spin the motor up. No need for the huge fancy battery they recommend.

Carl H said:

Put me in the not 1 list.

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Chances are I will never meet CW so his claim might strictly still stand, but they were one of the first things swapped out when I bought mine....

Carl H said:

I'm quite sure a good, new 10 or 12 amp battery would spin the motor up. No need for the huge fancy battery they recommend.

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The CCA of the battery is the critical figure for starter motors, the higher the better, AH is for how long you want to run the starter for, CCA for rotational speed as long as the wiring and starter can handle the amps.