Commando performance upgrade questions

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dparcell

I am starting a rebuild on a 69 Commando and am considering a number of performance upgrades. I could use some help figuring out the exact combination to use for a solid rideable (not racing) bike. I figure an electronic ignition is a given. I see lots on information on the forum regarding various choices. I am wondering about headwork, compression increases/new pistons, performance camshaft options and the larger diameter exhaust sytems I have seen on a couple of websites. I have the frame stripped and ready to go to powder coat and wonder about any upgrades, improvements to it that should be done now. Any experience/advice on any or all of the above would be appreciated as would any things that perhaps I am not thinking about.
Thanks.
Dave
 
A had question

I have tackled the same question starting with a dead stock 1975 850 Mk III Roadster with 6200 miles.

I'm 60 years old and didn't want to do continous development, I wanted to do it once and do it right. I started out speaking with the experts, which is a long story, which I'll tell when I present my finsihed machine to the forum in a few months.

As far as the engine was concerned I wanted throttle response from the lower end of mid range to redline (2500 and up). I wanted an engine that would go 10,000+ miles with non-invasive maintenance here is what I did:

Raised the CR to be at or near 9.8:1

Had the head flowed, turns out that the intakes are almost there, the exhausts needed to be opened. This inlcuded new valves, guides, seals, springs, keepers and retainers. The service that did the head work also set the installed height of the valve stems so that rocker geometry would not be compromised.

The head was milled .060 and the barrel was surfaced to mate perfectly with the head.

The barrel was overbored .020 while torque plates were in position.

I sent the rotating and reciprocating pieces to a specialist that is known for their balancing and rod work.

I sent the cases to CNW for cleaning and for their reed valve crankcase breathing system.

I am going to start doing the assembly next week. Prior to that I sent my torque wrenches out for calibration and have all parts cleaned and in dust free baqs. I will:

1) set the end play of the crank

2) Check the cam timing using the lobe centers

3) Check the ring end gap

4) check for valve/piston clearance

5) Check for valve to valve clearance

6) verify rocker arm geometry

When I am good with the above I screw it together. I will be using a Tri-Spark ignition system and Amal carbs (brand new ones).

If my assembly is done properly and my break-in is carried out judiciously I'll get 10,000 relatively trouble free miles--the transmission has been through a similar protocol and I am using a 520 X-Ring chain for final drive.

As I have two other bikes so these 10,000 miles should take me at least 8 years to put on, bearly $500/year from the engine's point pf view :shock:

All the best!!

RS
 
A good starting point would be the INOA tech digest. It has a list of recommended upgrades by serial number. For a '69 you definitely want new pistons as the originals are known for "dropping their skirts". New valves and guides will help with oil consumption, as Norton changed them fairly early on and added guide seals and stellite tips on the valve stems. If it's a low mileage bike you'll be amazed at the amount of crud in the sludge traps in the crank. There are some gearbox upgrades highly recommended - kickstart pawl and some of the gears were much improved early on. Upgrade the steering bearings to either later style or tapered roller bearings. If original the head steady will crack on you and should be replaced with either a later style or one of the after-market ones. Just these upgrades should give you a good, reliable bike. Add an electronig ignition and you should be good for quite a while. If you still have money left there are lots of other upgrades that are great, but it's easy to get into diminishing returns. Good luck!

Nelson
 
Best thing for a pre'72 engine is upgrade to FAG Superblend main bearings. Only buy genuine Norton gaskets, cheap imitation stuff is work done twice. The motor could be done to Combat spec for extra power, but use the later recommended parts post 72. The Combat in 71 was a bad year for pistons, cranks and cams.

Head intakes should be 30mm or 32mm Combat spec, 10:1 compression and ideally a PW3 cam. Remember, if you plane down the head, the pushrods may have to be shortened to compensate the rocker geometry.
Lots of good electronic ignition systems available, I've found the Boyer kit to be pretty good over many years.

Mick
 
I don't want to be a party pooper, but trying to make it perform more than it was designed to is (IMOHO) a waste of time and money. Make it reliable YES. When I look at the guys in vintage racing pushing a 30 year old motor based on a 60 year old design, I see a lot of time and money being spent, not a waste to them, this is what they like, but they are not reliable, when the engine lives through many races, the chassis gives up and when the chassis lives, the engine gives up. Don't get me wrong, I love these bikes and I love working on them, but even with an unstressed motor, they are never as reliable as an UJM.

RoadScholar made a good list of things to do to make it reliable and perform as it should which is most likely good enough to blast all the cars on the road (except the ones with big supercharged V8s).

Jean
 
littlefield said:
RoadScholar,
Are you keeping the stock cam?
Click to expand...

If not, what cam?

Who's doing the head work?
What data was used to determine the flow work?
 
I think it's kind of a shame to do that to a stone stock bike with 6200 miles on it. In the name of reliability? So many engines and expensive parts like heads have been trashed at the hands of people that supposedly know what they are doing. If it ain't broke don't fix it. It's your bike and you can do what you want with it but someday there will be no more stock bikes.

Grumpy
 
from you quote < I want a solid reliable rider > I would build a GOOD STOCK engine with attention to detail. stuff like Black diamond valves top notch guides and machine work. a good gear box rebuild and I prefer a belt drive primary for several reasons. The money spent on reliability and NOT performance is MUCH better spent. buy the INOA tech digest and READ, READ, READ. Some other things I like from a good rider stand point is a 520 O ring chain conversion ( I have 21,000 miles on mine ) a single Mikuni for ease of maintenance and so on.
 
MichaelB: I am using a Web Cam model 12a, my head work was done by Leo Geoff of the Memphis Motor Werks:
http://www.memphismotorwerks.com/index.php

batrider: A dead stock Norton has all the faults of a dead stock Norton. I believe that reliability and performance go hand in hand up to a point; I aimed at my impression of that point. I am not going to race it, hell it won't see rain or temps above 88 or below 60. My goal was to blueprint the entire motorcycle, kinda like a mechanical dissertation; something I have been wanted to do for over 30 years, but couldn't because of kids, mortages and career--those are behind me now. I want to show it off, see if I can inspire younger souls to want to do the same thing, kind of like living art.

All: I will be presenting my machine in text and pictures in about a month, you can be the judges.
 
I'd think that would work fine for your use R/S.
I think I may have been somewhat lucky with the combinations of parts I used in the past, but then I worked on each area until I was happy and it satisfied me.
If I were to do a Norton today I'd go lower compression, a milder cam, and perhaps a single Mikuni. Other parts would depend on the use of the bike and what you started with.
Way back when I fitted the upgraded valves, I believe we had bronze guides, better valve seals, and the good bearings. My dealer only sold the superblend at the time.
At this point I'd be building the engine for fuels with poorer octane that we may have to deal with in the furture.
 
RoadScholar said:
MichaelB: I am using a Web Cam model 12a, my head work was done by Leo Geoff of the Memphis Motor Werks:
http://www.memphismotorwerks.com/index.php

batrider: A dead stock Norton has all the faults of a dead stock Norton. I believe that reliability and performance go hand in hand up to a point; I aimed at my impression of that point. I am not going to race it, hell it won't see rain or temps above 88 or below 60. My goal was to blueprint the entire motorcycle, kinda like a mechanical dissertation; something I have been wanted to do for over 30 years, but couldn't because of kids, mortages and career--those are behind me now. I want to show it off, see if I can inspire younger souls to want to do the same thing, kind of like living art.

All: I will be presenting my machine in text and pictures in about a month, you can be the judges.
Click to expand...


Sounds like a nice, solid rider you're building.
Looking forward to seeng the pix.
 
Thanks everyone for the tips. Sounds like some great ideas. Sorry I didn't reply sooner. I can only get on here once in a while. Got to take care of life first. Did get to a local Norton Owners Club meet last weekend. Met a bunch of nice people and got some more ideas plus leads for local shops and the like. Going to be a long project but hopefully a lot of fun as well. I'm sure I'll be back with more questions from time to time.
Dave
 
Suspension ***

Probably the best investment you could make would be in upgrading the stock front dampers and the rear shocks. For the front, Cosentino engineering makes a kit you can put in your stock forks if you want the looks to stay the same http://www.cosentinoengineering.com/ind ... ge0019.htm or you could just graft on a modern sportbike front end complete with disks and wheel. The back can also benefit, but I have no information close at hand.

Jean
 
Jeandr, can I assume you've made the front fork upgrade? If so, how well does it work? I'm pretty sure I need to do something about my front and rear suspension, as I get a lot of unwanted jarring at highway speeds. The kit looks good, but the price leaves me gasping a little. I don't know if I need the upgrade that bad, or there might be other, less expensive alternatives available.
 
slupdawg said:
Jeandr, can I assume you've made the front fork upgrade? If so, how well does it work? I'm pretty sure I need to do something about my front and rear suspension, as I get a lot of unwanted jarring at highway speeds. The kit looks good, but the price leaves me gasping a little. I don't know if I need the upgrade that bad, or there might be other, less expensive alternatives available.
Click to expand...

No, I have not done it, but I know a racer who has and he says it was the biggest improvement in his lap times. When I compare the front suspension on my old Commando to even my 1977 Yamaha, there is a world of difference in smoothness and road compliance. The Roadholder forks were a major improvement when they came out in 1946, but they need a bit of help to compare with forks designed 30 years later not to mention forks designed just a few years ago.

I will see how it goes, but I may do it in the coming years if I find my Roadholders are too harsh for my old body.

For the back end, without changing a lot of things like the swing arm, the best benefit would be better shocks and I think there must be something better than the usual Hagon which in my own humble opinion are no better than the stock shocks, the only thing they have going for them is they are a bolt on replacement.

Jean

Another good read on front forks http://www.nocnsw.org.au/forks.html
 
Roadscholar , I'll be curious to see how yours turns out since I've been talking with Leo aout doing something similar to my Mk III . For anyone who has questions regarding Norton stuff I recommend him highly . He has the knowledge, and Memphis Motor Werks has the machining equipment to do state of the art work. One of the few benefits of living here :)

Ron
 
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