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JeffWed Oct-12-05 09:17 AM

  
"72 Combat- how can you tell"


  

          

Greetings, at the NTNOA rally last weekend I met a Norton owner who told me "all 72 Commandos with a disk brake are Combat model". I do not know the difference in the models, or how to check.

The bike was not sold to me as a "Combat Commando". It is a 72 750 that runs great! (bike ran without any problems during the rally, my work is paying off). Whats the story on the "Combat" thanks

  

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MichaelBWed Oct-12-05 11:31 AM
Member since Mar 18th 2009
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#1. "RE: 72 Combat- how can you tell"
In response to Reply # 0


  

          

I bought a Combat sight unseen a couple of years ago that the owner couldn't or wouldn't acknowledge it being a Combat. I thought strange because he was a long time Norton owner.

Combats have high compression, ported head, high lift cam and 32mm carbs. They haul @$$. These combos revealed a weakness in the crank bearings where the engines would self destruct. Consequently they have poor reputation. This is where the superblend bearing comes in. A Combat with superblends is a mighty nice ride. The later Combats came with superblends. Most early ones have been changed, but not all.

Combats are easy to spot. First of all, they had black barrels but barrels are easily painted. The Amals have 932 on the side. The head has a stamped C on the top. The easy spot is the spacing of the fins. The space between the head and barrel is noticeably smaller due to the shaved head.

Yes Combats came with disc brakes, but over the course of time many things get changed around.

HTH Mike

Mike

  

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dynodaveyWed Oct-12-05 02:13 PM

  
#2. "RE: 72 Combat- how can you tell"
In response to Reply # 0


  

          

A few added details:
All combats are 72MY , but not all 72 are combats. Genuine hiriders were not combat, and interpol and a few other standard bikes were not combat. The majority are combat.
The lowest number combat I have seen is 200205 which is earlier than some literature quotes.
It has a flat boss on the drive side with the SN, and NOT the cam end breather style case with sn stamped on the countour of the cases below the barrels.
The early ones have extra deep milling on the rear motor mounts bosses, and this leads to case cracking if the engines are stressed to much. By 206xxx or 208xxx (I forgot which) this defective machining process was altered to eliminte this stress riser.


  

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JeffFri Oct-14-05 01:35 PM

  
#3. "RE: 72 Combat- how can you tell"
In response to Reply # 2


  

          

Hi, what is 72MY? So, this bike is 202209 which is stamped on a flat area on the drive side, below the barrels. I do not know about the "extra deep milling bosses" or how to tell.

The bike has some real compression, from kicking it over (compared to other Brit twins I have ridden recently). I have a receipt for superblend bearings (I did not rebuild the engine). The barrels are black (who can say) and the bike came with a mik, so I cannot reply on the original Amal #'s.

Regarding spacing on the fins, wish I would have known that before last weekend's rally. There are 5 fins below the spark plug-- I do have some pics from last weekend, if anybody can tell from looking. Where is the "c" stamped on the head?

The reason I am asking is, it is my understanding (read somewhere) the Combat had higher gearing. I am planning to replace the sprockets & chain this winter. Does anybody know the number of teeth on the f&r sprockets (from the parts book rear looks like one-piece, with the rear brake hub). part numbers helpful, thanks Jeff

  

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MichaelBFri Oct-14-05 02:05 PM
Member since Mar 18th 2009
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#4. "RE: 72 Combat- how can you tell"
In response to Reply # 3


  

          

Jeff, You probably have a Combat. Someone made a point to give the receipt showing superblends for your piece of mind. The superblends are the main fix for Combats.

The C is in the the center of head facing forward. Remove the tank for a look.

The spacing I am referring to is the space between the head and the barrel. It is narrower than the head and barrel spacing of the castings.

The serial number fits.

I'll let Dave answer the 72MY, my guess is 72 Manufactured Year.

It just occured to me, is this a bike your considerng buying?

Mike

  

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dynodaveyFri Oct-14-05 02:31 PM

  
#5. "RE: 72 Combat- how can you tell"
In response to Reply # 3


  

          

72MY is "model year" since it does not coorespond with calander year.
This acronym seems to be quite common on modern bike bulleting boards such as ducati

My bike 202206 and it does have the sharp deep cut cases, so unfortunately, yours will also. I have only seen this machining flaw corrected toward the end of 72MY.

You can see this where the steel engine cradle bolts onto the back of the motor. It makes a stress riser there where the cases are quite thin and it is quite prone to crack if you flog (over rev) it a lot.
The fix is to have it heliarced when out and apart for overhaul.
All US 750s came with a 19t gearbox sprocket, combat included.
I put a 21t like many others do, for better cruising.

dd
nortons+
ducati
02MY MS4
92MY 907IE
92MY 907IE (916 power)

  

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JeffFri Oct-14-05 03:47 PM

  
#6. "RE: 72 Combat- how can you tell"
In response to Reply # 5


  

          

Ok, so there is no difference in the sprockets. I didnt see any separate listings in the parts list. Just interested to learn about the "Combat"

Actually, this is a bike I bought a couple months ago. Now it's running, licensed & insured, and I have been riding it just to enjoy before I tear into some restoration work over the winter. Still have a few things to sort, but I sure did enjoy riding on those east Texas roads! The roads in Dallas are flat (too many cars) but the 2-lane blacktops out by the lake have lots of hills & curves, low traffic. gorgeous. And I got a lot of interest, and positive comments from Norton folks at the rally.

cheers, Jeff

  

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Ty ParkerSat Oct-15-05 12:30 PM
Member since Mar 18th 2009
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#7. "RE: 72 Combat- how can you tell"
In response to Reply # 6


  

          

Just a thought, but if your going to replace your sprockets you may want to consider changing to a narrower 520 chain and sprockets so that you can use an o-ring or x-ring chain that will last many times longer than a standard chain(a 530 o-ring will rub). There are several places that have everything to make the change. Some offer to machine your rear drum/spocket, or you can buy one suitible to the 520 chain. Try www.clubmanracing.com.

Good luck
Tyrone

  

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JeffMon Oct-17-05 12:06 PM

  
#8. "RE: 72 Combat- how can you tell"
In response to Reply # 7


  

          

Thank you so much for pointing out the 420 O-ring chain mod. Thats why I am using this forum, for advice from real Norton folks!

So if I use the 06-2764 sprocket/brakedrum assy 42tooth, and match it with a 19tooth primary sprocket (both milled for 420) I can use a O-ring 420 chain, how many links?

I like the gearing on this bike, I realize that a 21T primary would lower the revs at speed. To be honest I dont forsee a lot of 100+ cruising on this bike (I prefer 2-land blacktops in Texas they are "FM" farm-market roads). In it's current state of tune the Commando eats those cool new mustang gt's, and walked away from the bonnevilles and tigers at the rallye. So I will keep the taller gearing

  

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dynodaveyMon Oct-17-05 01:31 PM

  
#9. "RE: 72 Combat- how can you tell"
In response to Reply # 8


  

          

Jeff
The 19t sprocket will not cruise at over 100. 105-108 maybe tops @ redline. even 80 seems uncomfortably revvy to me.

21t is if you want to do 70mph at a little over 3500rpm
dave

  

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RohanMon Oct-17-05 07:26 PM

  
#10. "RE: 72 Combat- how can you tell"
In response to Reply # 9


  

          

A 21T sprocket will give 60 mph at 3500 rpm.

To do 70mph at 3500 rpm you'd need about a 25 tooth sprocket. Since sprockets don't come with about 25 teeth, it would have to have exactly 25 teeth...... !!

Jist quoting from the manual.
opethiselps.

  

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Ty ParkerTue Oct-18-05 07:59 AM
Member since Mar 18th 2009
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#11. "RE: 72 Combat- how can you tell"
In response to Reply # 10


  

          

You may also consider a belt drive primary, which you also can get with a higher gear ratio. This raises your gear ratio before the transmission rather than after it, and puts less stress on the tranny.
Tyrone

  

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dynodaveyTue Oct-18-05 11:30 AM

  
#12. "RE: 72 Combat- how can you tell"
In response to Reply # 9


  

          

It very well could be my tach under indicates, but I also forgot of the ratio change from my belt drive primary.
At the drags the printout shows 92mph at 6300rpm(indicated) in 3rd gear.
dave
21t sprocket combat

  

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MichaelBTue Oct-18-05 05:28 PM
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#13. "RE: 72 Combat- how can you tell"
In response to Reply # 12


  

          

Jeff, The 520 chain won't work with stock sprockets. You'll need a different front and machine the rear. Yes, it is part of the brake drum.

www.clubmanracing.com has these in stock.

I prefer a 20t. sprocket. Less buzzy than the 19, easier on take offs than the 21.

My $.02

Mike

  

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JeffWed Oct-19-05 02:04 PM

  
#14. "RE: 72 Combat- how can you tell"
In response to Reply # 13


  

          

Greetings, by using the "taller" gearing the engine
will turn more revs at any given speed, putting it
closer to the "power band". Low and mid-range power,
tradeoff is top-end (which is fine)

(I do have lap times on record at Laguna Seca, but
that's different-- no cops, cars, or gravel) I just
enjoy ripping around on this Norton, it sounds
good, it's fast and the Ladies like it..

Glad I learned about the 420 chains for Commandos.
I will powdercoat the rear hub & polish the front
when I lace & true up the new alloy rims. Might as
well replace the sprocket/brake hub, mill it and
powder coat while I'm at it. (oh yes retrofit sealed
bearings) new chain & sprockets. But right now it's
88*, there is some good riding weather before teardown.

cheers, and thanks for the good information

  

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dynodaveyWed Oct-19-05 02:36 PM

  
#15. "RE: 72 Combat- how can you tell"
In response to Reply # 14


  

          

I believe your use of the term "taller gearing" is reversed, try and google "tall gearing" for adequate examples of definitions

even a combat has quite flat torque @ about 47ft/lbs.
HP will of course peak, but in stock tune, dyno printouts show torque is fairly flat 3K-5K+

  

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