Modern Enhancements to 750 Combat

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RedEvo

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May 23, 2009
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Hi,

I've got a 1971 750 Commando Combat. It was restored some years ago and is in decent shape although it hasn't been run for about two years.

I'm starting a process of fettling it for regular day to day use and I'm considering some modern enhancements that will make the bike more usable and more reliable. I'd appreciate other people's views on this. The specific enhancements I'm considering are:

1. Modern carb
2. Primary (and possibly final) belt drive
3. Replacement front disk brake
4. Upgraded electrics

I believe there's a 'black box' approach to electrics that replaces all the separate components such as zenor diode etc? Is this the case?

many thanks

d
 
The list is endless, hence the popularity of the Commando. There is always something that you can do.

It all comes down to two things, time and money. You can keep modding your bike until you run out of one or the other. Enjoy!
 
Welcome RedEvo,


RedEvo said:
I've got a 1971 750 Commando Combat.
Click to expand...


Most Combat spec. Comandos were manufactured in 1972, beginning at serial 200976, although of course the engine could have been changed, or Combat parts fitted to a 1971 model?
I believe the Combat spec. engine could be supplied to special order before the Combats were introduced on the production line? However the front disc brake wasn't fitted before the production Combats were introduced as far as I know, but again, the disc brake could have been fitted some time after your Commando was made?


RedEvo said:
I'm starting a process of fettling it for regular day to day use and I'm considering some modern enhancements that will make the bike more usable and more reliable. I'd appreciate other people's views on this. The specific enhancements I'm considering are:

1. Modern carb
2. Primary (and possibly final) belt drive
3. Replacement front disk brake
Click to expand...


Modern carb?

A single carb conversion could make your Commando more usable. Mikuni and Keihin single carb kits are available, as well as single carb manifolds to take an Amal Mk1 or Mk2 carb.

Belt drive?

Some owners prefer belt drive as they can be smoother and quieter than a chain, and a primary belt allows the use of a dry clutch.


Replacement disc brake?

There are many options available for upgrading the front brake, and how good that upgraded brake is, can depend on how much money you want to spend to a certain extent?



RedEvo said:
4. Upgraded electrics

I believe there's a 'black box' approach to electrics that replaces all the separate components such as zenor diode etc? Is this the case?
Click to expand...

There are various regulator/rectifier boxes available which take the place of the original rectifier and regulator (Zener diode) such as Podtronics, Tympanium, Boyer Power box, Sparx, and a few others. The ignition can be upgraded to electronic, and again there are several options acailable, such as Tri-Spark Classic Twin, Pazon Sure Fire/Smart Fire, Boyer MkIII and MkIV, Micro Digital and Micro Power, and Sparx.
LED lights, high power three-phase alternators that will run brighter headlamps and sealed gel or AGM (Absorbed Glass Mat) batteries are also popular upgrades.
 
1. Modern carb
2. Primary (and possibly final) belt drive
3. Replacement front disk brake
4. Upgraded electrics

I'm on my second '72 750 combat model. First was bought in '73 with 300 miles on the clock (201123). Current one I've had for 12 years and did a total rebuild with mods in 1998.

Carb - I prefer the original Amals, mine have been stainless sleeved by Mike Gaylord (now retired). Personal preference for a combat is no single carb. The combat is a performance engine. Single Mikuni is great for an 850.

Primary - again personal preference. How much stronger a drive does a Commando need than the original three row chain. Considerations of weight or noise, I doubt if it makes any significant difference.

Replace front disk brake - more brake is always better. I have no issues with the stock disc.

Upgrade electrics - my only comment is Dyno Dave convinced me in 2002 to switch out the Boyer I had to a Lucas RITA (no longer sold). The reason is combat's are sensitive to the advance curve. Too fast causes engine pinging (detonation). The RITA has a much closer advance curve to the original auto advance unit. Not sure about some of the newer electronic ignitions, but consider this. Also many have experienced low tension lead breakage on the Boyer units...causes back firing and difficult to diagnose as the wires break inside the insulation, can't tell looking at them.

Engine breather - I did the modification moving the oil pick up point rearward and the breather to the back of the timing case (850 style). It's a lot of work and I never noticed any improvement. The argument is with the "combat" breather wet sumped oil goes up the breather pipe...so what it still gets back to the oil tank.

Modern oil seals - kick start and gear shift shaft and tachometer drive - recommended. Dyno Dave's clutch pushrod seal - very recommended, you'll never have clutch slip again.

Regards,

David in CA
 
Hi,

Many thanks for all the great replies. Just to correct my original post the bike is a 1972 not a 1971. I was confusing it with my previous Commando (a basket case I never quite got round to restoring!). I'm actually assuming it's a Combat because of the front disk brake (the Norvil website suggested "Optional disk brake and combat engine." so I assumed it was a combat bike, is there anything else that would easily distinguish it as a Combat? The engine number is 201276 and the frame number matches it.

I can see this place will be a great source of help as I start the process of modernising the bike.

d
 
RedEvo said:
I'm actually assuming it's a Combat because of the front disk brake (the Norvil website suggested "Optional disk brake and combat engine." so I assumed it was a combat bike, is there anything else that would easily distinguish it as a Combat? The engine number is 201276 and the frame number matches it.
Click to expand...

In addition to the disc/disk brake, other clues leading to it being Combat spec. at that engine number would be:

32mm carbs
Skimmed cylinder head, (many Combat heads had a "C" stamp on the top)
Black cylinder barrels
2S camshaft.
 
hi redevo,if its a combat it should have 32mm inlet ports and carbs, it should have the letter C stamped on the head around the right hand side rocker cover area , it should have a comp ratio of around 10 to 1, inside the engine should be a 2s cam (not ss) this can be checked against the cam timing of your bike without stripping it down,in the uk i remember the most combats were interstates but any variation could be ordered, the engine breather should be on the back of the crankcase
 
chris plant said:
it should have the letter C stamped on the head around the right hand side rocker cover area ,
Click to expand...

I think most of them had the 'C' stamped in the centre of the head? broken link removed 'C' can be seen in photo, bottom right.




chris plant said:
the engine breather should be on the back of the crankcase
Click to expand...


But that wouldn't really identify it as being a Combat model, as all '72-'73 750 models had that breather.
 
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The space between the fins where the head and cylinder meet is a dead giveaway. Equal spacing is a non Combat. The Combat will have a smaller space between those fins as opposed to the pattern of the rest.
 
hi lab your probably right, but i think we are agreed on the letter c stamped on the head and the breather on the back of the cases
 
chris plant said:
but i think we are agreed on the letter c stamped on the head and the breather on the back of the cases
Click to expand...

Well...I must admit I don't quite see how the rear breather could be used to identify a Combat from a standard '72 model,-if they all had them?
 
JimC said:
The space between the fins where the head and cylinder meet is a dead giveaway. Equal spacing is a non Combat. The Combat will have a smaller space between those fins as opposed to the pattern of the rest.
Click to expand...

That was easy!

broken link removed
 
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I guess I should correct my earlier post about fin spacings. I should of said that the Combat fin spacing is less than the non Combat. I don't know for sure that the non combat had exactly even spacings. I do know I can spot the difference.
 
chris plant said:
lab thats true, but if it has,nt got that breather its not a combat
Click to expand...

OK then, that's turning it around a bit, as we already knew that it's from '72 production by the serial number, didn't we?


chris plant said:
looking at redevos pics, the breather is 850 style and it looks like a single carb
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Single carb is certainly evident, and the breather has been modified, and is "850" style in its positioning, although the actual 850 breather stub arrangement differs to what is shown in the photo.

http://www.oldbritts.com/n_c_case.html
 
JimC said:
I guess I should correct my earlier post about fin spacings. I should of said that the Combat fin spacing is less than the non Combat. I don't know for sure that the non combat had exactly even spacings. I do know I can spot the difference.
Click to expand...

None of them are exactly equal, but the reduced barrel to head fin spacing on Combats is more noticeable.
 
JimC said:
I guess I should correct my earlier post about fin spacings. I should of said that the Combat fin spacing is less than the non Combat. I don't know for sure that the non combat had exactly even spacings. I do know I can spot the difference.
Click to expand...

Jim what do you reckon from the pic I posted a few posts back?

d
 
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