New project, need some opinions

That's gorgeous. Any pictures of the left side?
My project is based on a stock Atlas.

seattle##gs said:

I have bits and pieces laying around and would like to make use of them.
First, I have an 850 motor that needs to be built. I also have a Megacycle 56000 cam and lifters in like new condition. I do not have any experience with this cam. Is this streetable? Does it have a good idle, approx 1200? I am mostly in the 4000 rpm range or lower. Is this cam impractical? I have no complaints with the original Norton cam. What is your experience?

2nd...Molnar products sells engine plates to fit a Commando engine in a slimline frame. I can either have the motor sitting vertical or sloped. The sloped version allows the Norton logo on the timing side to sit horizontal instead of vertical which, visually, is a big deal. I also see that it requires the use of the Commando primary cover. Try as I might I have not found any pictures of this arrangement. Can anyone out there locate photos and post them? Done it yourself? Pros and Cons?

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Weld the logo up
And re engrave it level as Ludwig has done

Maybe you should start a reader poll?

FWIW I vote canted.

Commando motors go faster leaning forward the way they should be lol.

When I first started too built my Commando/Featherbed back in 1980 I wasn't working at the time so money was tight why it took me 2 years to build, but everything was cheaper back then, I got my cam built up and a 2S grind and crank balanced for under $100 for both, new Hepolite 40th pistons were cheap as well, then early 82 I got a job at a Tec college where I had access to motorcycle section with 2 very experienced teacher and access to good machinery where the rebore was done and all my head work was done, to guided oxy cutter to cut all my engine plates, so worked out well for me.
I was working there for 31 years and become a TA to the maintenance fitters where I learned a lot and made a lot of improvement over those 31 years till I took a redundancy in late 2013 when I retired, but over those years I built a new workshop/shed up and tooling from the old fitter shop before they closed the fitters workshops.
But before I retired and the kids all grown up I spent a bit of money buying upgrades for the Norton with Lansdown internals for the frontend, full front brake upgrade, new carbs and the best of all the Joe Hunt maggie, as for my motor it's basically the same set up inside but I had to change the crank cases from a few fractures around the main seal area and a broken piece where the front middle stud broke off the crank case, (doing to many burn outs in my youth).
I wish all of Jim's lovely bits and pieces were around back in the 80s, these days I just couldn't justify the spending too buy all his goodies, but my motor has proven itself to be very reliable and has never let me down in the 44 years when I first built it and hopefully will outlast me.
My Norton is showing its age now but it still goes as good as the day I built it with a few later upgrades to it, but it has scrubbed up good the last few days while it's been raining and I given it a good clean and polish, for an old girl she dolled up nicely, well for me anyway lol.

Ashley

ashman said:

Commando motors go faster leaning forward the way they should be lol.

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Agreed, plus you are moving some of the weight forward

I would have the motor sloped forward. A Manx always handles better than a Triton. The difference is the Manx has it's centre of gravity further forward, - as you accelerate and brake - in the vertical plane the frame rotates fore and aft around it's centre of gravity. Light in the front can feel not so good - destroys confidence.
My Seeley 850 has rigidly mounted motor. I rebalanced the crank by screwing a threaded steel plug into the hole in the counterweight, with blue loctite. Factor 72% works well.

Sloping the engine forward LOOKS like it can go faster. If nothing else, the head always gets there first. That is why it is called "a head". Insert smiley here

Go for the light weight rods if you go to splitting the cases. Then find the proper balance factor for the combination.

Slick

Here is some opinion-
Aren't the long steel rods all quite a bit heavier than stock Commando aluminium? Even if only the small end weight is considered, the stock rods are still the lightest thing going, unless things have changed recently.
If you aren't racing then the al rods are plenty strong. Even if you are racing the alu rods are said to be good for up to 90 bhp. They are good rods!
We posed the question at our breakfast group, " has anyone ever broken a stock rod in their Commando or do you know of this happening on another Commando." We came up with about 20 bikes, lots with issues , but no broken rods, other than my cousin's new Combat, which broke its crank and then the rods.

Ken Canaga put up a very detailed list of piston and rods weights awhile ago.
I would look at getting the lowest possible combination of rod and piston weight. That might be with a lightweight piston fitted to the stock rods.
From Ken's info, M.A.P. makes a very lightweight 850 piston that will fit the stock rods. By my numbers this is about the lowest overall rod and piston weight available for an 850.
You'll want to do your own research to check my numbers.
One member reported that he had very good luck with these MAP pistons for stock rods. He also said he had problems with the M.A.P. long rod/ short piston setup on another Commando engine.
Whatever you end up choosing for lightweight 850 pistons and rods, the end result will be a reciprocating weight similar to a stock 750 Atlas.
I would then expect a similar vibration level to an Atlas. Dynamic balancing might help a little, but I don't think it will work wonders.
If it did, Norton would never have bothered to come up with the rubber mounted Commando.


Glen

seattle##gs said:

I want to use the lightweight JS pistons and get the motor balanced. He offers lightweight pistons for stock rods now. The balancing cost is about $300 including shipping.

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The smoothest setup of all is the lightweight pistons and longer rod combo.

worntorn said:

Here is some opinion-
Aren't the long steel rods all quite a bit heavier than stock Commando aluminium? Even if only the small end weight is considered, the stock rods are still the lightest thing going, unless things have changed recently.
If you aren't racing then the al rods are plenty strong. Even if you are racing the alu rods are said to be good for up to 90 bhp. They are good rods!
We posed the question at our breakfast group, " has anyone ever broken a stock rod in their Commando or do you know of this happening on another Commando." We came up with about 20 bikes, lots with issues , but no broken rods, other than my cousin's new Combat, which broke its crank and then the rods.

Ken Canaga put up a very detailed list of piston and rods weights awhile ago.
I would look at getting the lowest possible combination of rod and piston weight. That might be with a lightweight piston fitted to the stock rods.
From Ken's info, M.A.P. makes a very lightweight 850 piston that will fit the stock rods. By my numbers this is about the lowest overall rod and piston weight available for an 850.
You'll want to do your own research to check my numbers.
One member reported that he had very good luck with these MAP pistons for stock rods. He also said he had problems with the M.A.P. long rod/ short piston setup on another Commando engine.
Whatever you end up choosing for lightweight 850 pistons and rods, the end result will be a reciprocating weight similar to a stock 750 Atlas.
I would then expect a similar vibration level to an Atlas. Dynamic balancing might help a little, but I don't think it will work wonders.
If it did, Norton would never have bothered to come up with the rubber mounted Commando.


Glen

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I doubt that Norton was too concerned about balancing. I purchased the Atlas in 1986 with low miles. It had sat in a warehouse for ages
(in Willows California) and I suspect it was because of the vicious vibration...I would say almost unrideable. I had the crank balanced, Commando pistons, a single Mikuni, and a Boyer. That made it a pleasant bike to ride, even for several hours.
I have built 2 motors with the JS piston and rod combination and the results are amazing. I rode one for 2 hours on the freeway to the Canadian border delivering it to the owner. In one brief spot I got it up to 85. This was beyond anything Norton could have imagined.
If this was a race bike it would be no question to use the JS parts. HOWEVER...call me crazy but...I like the feel of the balanced stock motor. It will vibrate but not terribly and retains the Norton "feel". It is very rideable even for a day's ride. There comes a point where I've changed a Norton too much. This point is very up to the individual. I imagine only 2 or 3 people will agree with me.

seattle##gs said:

I doubt that Norton was too concerned about balancing. I purchased the Atlas in 1986 with low miles. It had sat in a warehouse for ages
(in Willows California) and I suspect it was because of the vicious vibration...I would say almost unrideable. I had the crank balanced, Commando pistons, a single Mikuni, and a Boyer. That made it a pleasant bike to ride, even for several hours.
I have built 2 motors with the JS piston and rod combination and the results are amazing. I rode one for 2 hours on the freeway to the Canadian border delivering it to the owner. In one brief spot I got it up to 85. This was beyond anything Norton could have imagined.
If this was a race bike it would be no question to use the JS parts. HOWEVER...call me crazy but...I like the feel of the balanced stock motor. It will vibrate but not terribly and retains the Norton "feel". It is very rideable even for a day's ride. There comes a point where I've changed a Norton too much. This point is very up to the individual. I imagine only 2 or 3 people will agree with me.

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Makes sense to me. It’s not what I DO perhaps, but I certainly understand your logic.

seattle##gs said:

That's gorgeous. Any pictures of the left side?
My project is based on a stock Atlas.

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This is a picture of the left side. These pictures are when the bike was last in road race trim back in 2007. It's currently set up for land speed racing, but I'd like to eventually turn it back into a street bike.



This is what the bike looked like when I bought it in 1983.





Ken

worntorn said:

Here is some opinion-
Aren't the long steel rods all quite a bit heavier than stock Commando aluminium? Even if only the small end weight is considered, the stock rods are still the lightest thing going, unless things have changed recently.
If you aren't racing then the al rods are plenty strong. Even if you are racing the alu rods are said to be good for up to 90 bhp. They are good rods!
We posed the question at our breakfast group, " has anyone ever broken a stock rod in their Commando or do you know of this happening on another Commando." We came up with about 20 bikes, lots with issues , but no broken rods, other than my cousin's new Combat, which broke its crank and then the rods.

Ken Canaga put up a very detailed list of piston and rods weights awhile ago.
I would look at getting the lowest possible combination of rod and piston weight. That might be with a lightweight piston fitted to the stock rods.
From Ken's info, M.A.P. makes a very lightweight 850 piston that will fit the stock rods. By my numbers this is about the lowest overall rod and piston weight available for an 850.
You'll want to do your own research to check my numbers.
One member reported that he had very good luck with these MAP pistons for stock rods. He also said he had problems with the M.A.P. long rod/ short piston setup on another Commando engine.
Whatever you end up choosing for lightweight 850 pistons and rods, the end result will be a reciprocating weight similar to a stock 750 Atlas.
I would then expect a similar vibration level to an Atlas. Dynamic balancing might help a little, but I don't think it will work wonders.
If it did, Norton would never have bothered to come up with the rubber mounted Commando.


Glen

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Vibration is not an issue when the crank balance factor is 72%. All that happens is trhe bike moves backwards and forwards when idling. Other than that, it feels lovely. I get a real buzz when the motor smooths out and starts to fly, but it usually starts to do that at about 4000 RPM. Are you building a sports' bike or a tourer ?
Motor scooters do not vibrate much. I would rather have an Atlas, but sales' figures might suffer.

$5000 spent on a decent gearbox might bring more performance than when it is spent one engine mods. Commando engines are fast enough. Even with a 4 speed wide ratio gearbox, they will stay with most 70s two-strokes. One of my mates said ' if you have a torquey motor, you do not need a close ratio gearbox. - Pure speculation ? The standard box in the Commando is useless for anything other than slow stuff. When I fitted the $700 Manx cluster into my Seeley 850, it immediately became competitive, but it needed the Commando low first gear. The gap between first and second would not be insurmountable. I was not thinking when I bought the 6 speed TTI box.

To me. my 850 motor is a joke. I never believed in it, but now I am amazed that it is so good without much modification. My first race bike had a 500cc short-stroke motor which had everything done to it - it was extremely fast, and with a 6 speed box,it would have been unbeatable. The Commando 850 motor is ten times better. - NO ANXIETY !
When you race, it pays to know the characteristics of the bikes the other guys are riding - then you know where they can get you and where they cannot.

acotrel said:

Vibration is not an issue when the crank balance factor is 72%. All that happens is trhe bike moves backwards and forwards when idling. Other than that, it feels lovely. I get a real buzz when the motor smooths out and starts to fly, but it usually starts to do that at about 4000 RPM. Are you building a sports' bike or a tourer ?
Motor scooters do not vibrate much. I would rather have an Atlas, but sales' figures might suffer.

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Vibration isn't an issue until you want to hop on an 80mph Freeway for about 50 or 100 miles to get somewhere.
The speed in the slow lane is usually around 85mph, so if you don't want to get hit from behind, best to do 85 mph or so. At that sustained speed a lot of things show up, numbing parallel twin vibration being one of them.
A lot of vintage motorcyclists never go on those freeways as their bikes just aren't up to it. I seem to end up on them now and then, usually as part of a bigger trip.

Glen

acotrel said:

The standard box in the Commando is useless for anything other than slow stuff. When I fitted the $700 Manx cluster into my Seeley 850, it immediately became competitive, but it needed the Commando low first gear. The gap between first and second would not be insurmountable. I was not thinking when I bought the 6 speed TTI box.

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How would you know Al as in your own words you have never ridden a road going Commando, my stock Commando GB works pretty good on the road, it copped a caning in my younger days with Friday/Saturday night burn outs and high speed runs, its not slow at all even with the 19 tooth front sprocket, not everyone here is racing around a race track, but we do ride them and some of us ride very hard, and things do wear from long hard riding same as anything, in 48+ years I have only been in my GB to replace the blown lay shaft bearing at 12k miles, 4 kick start pawls, and a new kick start gear where the pawl sit wore the gear round and was wearing the pawl out, no problem since I replace the KS gear that was over 20+ years ago, I also replaced the kick start shaft where the spline was chewed out from the kicker getting lose all the time, haven't had any problems since mounting a RGM T160 folding kicker it stays tight on the spline.
As I say a stock Commando GB works quite nicely if you look after it, they are such a smooth gear change as well, as long as the clutch is set right, my stock GB has over 160k miles on it and its been soooo long since I been inside it, a stock Commando GB slow, no way even with a high compression motor mine does pretty good and it has put up with my hard riding and long life in my hands with very little maintenance.
So Al you never know till you rode a road going Commando, although mine is in the Featherbed frame it still runs all Commando gear.

If you want more performance out of a Commando engine what it pulls makes a difference, regardless of what frame is holding it. I don't know where in the rev range, the power band of a normal Commando is, but the overall gearing can always be adjusted to suit. With close ratio gears the acceleration of the bike will always be faster, especially when you pull out to pass another vehicle. With wide ratios some bikes feel as though they have stopped when they hit a breeze.
My mate used to pre-delivery on Commandos and H1 and H2 Kawasakis. They used to road test them on one of our tourist roads. The Nortons kept-up with the Kawasakis, which says to me, the Nortons are potentially much faster. Their gearbox is not good. Because I had one, I tried to race with it. The bike was too slow everywhere. With the Manx close ratio cluster, it was perfect everywhere except in a clutch start race. If I had a road-going Commando, I would use a manx cluster with the Commando first gear, and I would rebalance the crank. I think it would be excellent.
$730 was all the Manx cluster cost - that is cheap for the improvement to performance.