Another rescue!

Finally got the Combat finished and running - Sounds quite a bit more snarly and rorty than the 850, but it runs!

When I finished the 850 I took video of the first start and it obliged by firing right up. I didn't bother with the video this time, but it was a first kick starter 8)
It's running a Pazon ignition, and although it's not quite as well behaved around tickover as the 850 with the Trispark, it's still got a good, reliable idle - I expected it to be worse.

This is what I started with last year (with later engine installed):





And here's the result after the application of a little effort and huge amounts of cash :roll:
Sorry for the grainy images - I'll get some more in proper daylight.









As a kid I always held the Combat as 'THE' iconic Commando, and was more than a bit curious as to how different it would be to the 850.
It's very early days yet (only 30 miles so far to the MoT station and back via the local back roads), but I'm really impressed - it's certainly quicker all round than the 850 at back-road speeds, and I arrived home with a huge grin on my face. Apart from the clutch adjuster backing off and the gear lever not returning to neutral for the first few miles (self-remedied), it's been spot on.
No hint of The Weave (yet) - it's rock solid with a 3.60 TT100 on the front, which may be down to the low bars putting more weight on the front, perhaps?
Looking forwards to getting it run in so I can give it a proper try out on the open road :twisted:

I restricted myself to the 'bare minimum' sensible upgrades: Hemmings-type layshaft roller, X-ring gearbox cover seals, Pazon ignition, Engine breather relocated to back of timing chest and scavenge mod to crankcase, MIke's XS PCV breather, RGM re-sleeved front brake with Ferodo pads (which work very well), MkIII Vernier isolastics and box-section head steady.

No leaks so far (there, I've said it )

You're turning into one of our restoration experts! Or maybe you are The Expert. Nice job. Which Pazon? Sure-fire? Are the Combat and the 850 set up with the same counter sprocket? It does make a difference!

Russ

Great job B+. Can't say more. I'd love a Combat in a 71 FB mode.

You sure turned a turd into a sweetie pie. Combats are The Cream of the Commando Crop to me. Fiddle the float levels up while still keeping pilot turns below 2 for best idle. Diddle the inital timing till hints of back fire starts then retard a tad so just don't. Notch or slope cut the back side of spray tubes. Fit a richer #3 slide. Then see how nice Combat is in low down grount tight back road spunK. Once run in well, might get addicted to the extra piston kicking in near red line. I liked 20T sprocket for all around joy on factory Combat power and weight. Pulls longer in lower gears and a bit longer legged rpm at curise.

Andy, where do you find the time?...Nice job! are the second pair of Lansdowne's holding the beast in check :?:

Wow, quite a transformation, you are putting my rebuild to shame As you alluded to, the bill must have been high

Are those Exhaust roses the ones from RGM, and did you mount the breather valve on the back of the timing chest, or is that just the breather outlet?

Looking forward to more of your pictures!

Peter

Looks great!

Looks like we have at least 3 or 4 really good entries for "Most Improved 2013" already, and it's only July!

Thanks for all the kind words, it's appreciated

The Pazon is the Sure Fire, and I just strobed it without needing to touch it! Spot-on at 31 degrees as the bike gently jack-hammered its way backwards across the yard.

I binned off the 19T gearbox sprocket and went for a 21, so it's the same as the 850, which has the dreaded 'noise regs' 2nd gear pair. Don't let anyone try to convince you that the later gear set offered a 'better matched' set of ratios. I have to let the 850 drop to virtually tickover in 2nd before I change down, otherwise it can occasionally get a bit sideways.
The 750 is far better balanced.
As for finding the time... it took me a year, so not a hugely rapid transformation - the Landsowne dampers are now residing in this, which will probably take...a year!



Judging by my wife's suddenly increased interest in the contents of my garage, I'm fearful that something will have to give, and not the family car :roll:

The breather on the timing chest is the standard '72 type, and the PCV is located behind the airbox - it's better to have it closer to the engine, but it's not very pretty, and works fine where it is - well hidden.
The exhaust roses came from Mick Hemmings, CNC machined from solid.

Here's a couple of daylight shots - I'll stick some more on the Photo topic 'sticky'

Beautiful work,well done

I am a wee bit confused on the breather. My '72 Combat has the breather off the back of the crankcase. The Timing chest is sealed in the mag location.
Not that it really matters. I assume you took the 850 motor for another project. Let me know if the wife starts throwing stuff out, you could send it to me.

I am interested to hear your reports of the Pazon vs Tri-Spark. It makes me think I should spring for new carbs and stop worrying about the idle stabilization.


Russ

rvich said:

I am a wee bit confused on the breather. My '72 Combat has the breather off the back of the crankcase. The Timing chest is sealed in the mag location.

Click to expand...

I believe what B+ means is that it's the standard '72 breather relocated to the timing chest-a reasonably common modification which doesn't necessarily require the "blanking plate" timing side case.

http://www.oldbritts.com/n_c_case.html

rvich said:

I am a wee bit confused on the breather. My '72 Combat has the breather off the back of the crankcase. The Timing chest is sealed in the mag location.
Not that it really matters. I assume you took the 850 motor for another project. Let me know if the wife starts throwing stuff out, you could send it to me.

I am interested to hear your reports of the Pazon vs Tri-Spark. It makes me think I should spring for new carbs and stop worrying about the idle stabilization.


Russ

Click to expand...

Russ,

There's a fair bit of information out there regarding the Combat ('72 to be strictly correct) breather system.
It had 2 main problems, the worst being the oil scavenge being located at the front of the crankcase, and the breather being located where all the oil would gather.
Under hard acceleration the oil would migrate to the back of the crankcase, hence no scavenge, and it would then be pumped out of the breather.
Hence the 'hand-grenade' reputation - empty oil tank and oily back tyre - great combination :shock:

I wonder if it was some Norton Engineer's 'last laugh' before walking off the job?

One of the solutions is this (as per the Old Britts link above) - in all the sordid detail :roll: :

There's a huge chunk of alloy at the back of the LH case which needs to be hogged out, revealing the rear scavenge drilling on the RH case

Original case with area to be removed marked out in pencil:



Loads of swarf later:



Lots of Dremelling later I got rid of the steps and blended it all in.
Hopefully this explains how it works - essentially the forward scavenge is deleted and the rearward hole gets revealed.



Finally the forward hole was tapped and plugged with a good dose of Loctite. I also gave the cases a good clean at this point :wink:



Blanking plate fitted to original breather location:



And finally, breather relocated to back of timing case - A couple of holes were also machined into the timing chest either side of the idler gear to provide the air path



I know CNW also do Jim C's very nice breather which puts a PCV on the original location - a neater solution for sure, but I guess the scavenging issue would still need to be addressed?

I still wonder WTF they were thinking about when they came up with this design!

Regarding the Pazon/Trispark; I can't really compare because of the different CR and vastly different cams, but I'd like to put the Trispark on the Combat to see if it improves the idle - maybe One Day

One thing I know about in Combats and none of them or non-Combats made in that run had any other breather but the low down bottom feeder baffle which was common to move to the magneto area, as I did mine. Please study the '72 case a bit closer to see you do not have to remove the deflection dam as it only goes to the vertical seam so completely free oil path open past the R hand side. Just need to JBW the front drain and create new one by driling down enough to expose the sump passage in the TS cover. The tricky thing would be how to afix a screen in the tight space that'd not become part of the stuff chewed and swallowed by drain or making it to the pump gear grinder. Does not have to be a very fine screen just filter big enough stuff that could bind in the passage or bother the gear faces in pump much. Mine have swallowed and digested Combat cam thrust washer tabs but they were bronze not steel pieces of rings or lifters or rod bolt chips and caps etc. Of course likely no more Combat Bombs anyways if they made it this long and also recieved loving recovery.

To say the PCV works better close to engine than to oil tank is like saying a grenade works better held close to chest rather than out arm length. I'm sure modern science could detect the slight delay in vaporizing your vitals but not so you could detect to matter one whitworth. The most efficient valve may lower pressing in 6 cycles while the valve near tank may take a dozen, sheeze. If crank pressure is somewhat below ambient then its enough but the slightly more efficient location, if it even does work better, just means ya can get away with more ring wear blow by before smoking.

I find Combat 2S cam can stand a bit more CR on 87 octane response and less oil weep by removing the base plate or gasket for closer fit and use flame ring or no head gasket, then diddle the push rods for rocker centering. A Combat is a fast burn set up compared to others so 31' adv may be shooting its power in the foot fighting advance flame front pressure before TDC. Would take stop watch and measured distance to fine tune much further than what you already enjoy though. Mine like 29' best. There should be a bit more Pat Pat Pat to the exhausts than the Puff Puff Puff of others.

Trouble with Combats to me is about where others feel like really starting to work to reach the ton the ole Combat is getting more and more responsive to throttle so it just doesn't feel like ya straing it so why let up...

Thanks for the breather info. I did misunderstand the comment and thought yours came equipped with the breather on the timing chest, more like the 850s. I suspect that Comnoz's breather on the back of a '72 case would allow enough oil to return to the tank that it might be more efficient than the pump. The biggest problem I have is that the filter is still in my breather and I am reluctant to tear it down far enough to get it out. Thus my oil really does stop flowing back to the tank in high revs.

Swap out those ignitions and give us a report!

I noticed you didn't bite on my offer to help clean out the garage. :wink:

Russ

Every Combat and non Combat Commando owner needs to have this background under their belt, plus the Combat transformer and Tunnel of Love.
All the errors and warrantee work put Norton so behind it never really caught back up. Educational on one thing leads to another and another. To me the Cream of Norton crop, once upgraded a good bit.
http://i283.photobucket.com/albums/kk31 ... ph0003.jpg
http://i283.photobucket.com/albums/kk31 ... ph0004.jpg

Hobot, I clicked on and read with great interest the links to the history of Norton's problems with the Combat configuration.

What a nightmare the Combat was for everyone from owners to dealers to the factory.

Your article clearly points out what a poor design the Combat was from the beginning, what with the horridly low bearing life of some 4000 miles to the problems that the higher compression and higher lift cam inflicted on the auto advance unit and jerking cam chain.

Interesting that the article pointed out that Combats had a top end of 108 mph at 7000rpm and that the later (850) motors were stronger in top end, that was my experience owning both also.

I owned two Combats and I too had the main bearings go to hell at about 6000 miles, along with the auto advance unit stuck on full advance causing starting kickbacks every time and frequent cam chain tensioning.

The Combat was an embarrassment to Norton and very very costly to warranty the repairs needed.

In my opinion, it was clearly the worst of all Commandos for major rapid wear and "reliability".

Fortunately, Combats now have had the bearings replaced and a larger front sprocket fitted, both moves greatly improving the stress on the motor.

Norton also beefed up the swing arm on the new 850s, and extended the wheelbase a little bit to improve handling further. I have always felt my 850s were stronger and quicker than than my Combats, once they got off the line. The Combat was quicker off the line only because it had the smaller 19 tooth sprocket, but then my 850 was stronger all the way to and including top end.

Today, with a larger sprocket and electronic ignition or later style mechanical ignitions along with the bearings replaced, the Combat can be made every bit as reliable and trouble free as the 850s, which were the direct result of the factory recognizing the mistakes it made with the Combats, and improving on them.

" Don't let anyone try to convince you that the later gear set offered a 'better matched' set of ratios. I have to let the 850 drop to virtually tickover in 2nd before I change down, otherwise it can occasionally get a bit sideways. "

The tricks to throw a higher first in it too . Theres some N.o.C. thingo , where maybe you loose another tooth on one cog of 2nd ,
The Highest ? ' kickstart ' first is used . Any smaller & the pawl wont go in , so its not there for it . Gets a fairly matched set of ratios .

Details probly in the N.o.C. service notes .

Hey B+ can you Tell me about the dual disc set up on the bike with the orange Dunstal tank??

If just pussy footing around the 750 2nd ratio is about right, but if kicking up heels it runs out of rpm before torque does and downshifts from 3rd can skip rear out of traction if not feathering throttle release to avoid full engine drag. The tall 1st gears the close ratio racers use is so small dia there is not room for the inside ratchet teeth, so no real racer has a kicker installed. For going up against others in twisties below the ton the taller 2nd and say 20T sprocket really wake up a Commando in the 45-85 mph zone or even faster if ya run into red zone some. The main downside of AMC box to me is lack of lube to the sleeve bushes except for splash lube when in 4th. I love the passing gear 2nd pull but have eatten up the bushes enjoying it too much but the un-joy of spanked sports bikes made it so so worth it while it lasted...