true or false

The thing I discovered about the 850 motor is it is very deceptive. When you ride the bike, it gives the impression the motor is giving it's best, however it spins-up at the same rate regardless of the overall gearing The gearbox and how you use it, is extremely important.

ashman said:

I use too anneal all my copper head gaskets but the last time I removed my head (a very long time ago) and forgot to anneal my new copper head gasket and remembered after torquing it all down so left it alone, well that was over 15 years ago now and have only retorqued the head once at 500 miles and a few years ago when a slight seepage started (2 large head bolts were lose), so far the un annealed copper head gasket hasn't leaked, 15+ years (been that long can't remember when I did it lol).
As for balance factor when I converted my 850 motor to the Featherbed frame back in 198/82 and hard mount engine plates, my crank was balanced at 72%, I wasn't there when the old English gentleman done it, but my Commando/Featherbed is smooth as but at some points of the rev range it does get some vibration but only in 2 spots of the rev range and for only a few second when revving through those 2 points, it always smooths back out past those 2 spots, my motor is leaned forward same as the Commando, I did the conversion from 1980 to 82 and had been an everyday ride till 2013 when I brought a new Triumph Thruxton, but the Norton is ridden regularly and is my hotrod and fun bike.
If it was bad with vibrations I would have sold it a long time ago but it's not, its a very comfortable bike and can be ridden all day and has done many of long travels and nothing shake off it and exhaust flanges stay tight without any mods to the flanges.
My motor is built for the Featherbed running a 2S cam profile, major port work, still running the original valves, bigger carb jets and 40thu oversize Hepilite flat top pistons that had very tight final hone to bore to piston clearance when done as well the crank balance at 72% and a stock 19 tooth drive sprocket.
This set up has worked well for me and I was lucky I was put on to a crank balancer who knew what he was doing and knew all about what I was wanting to do with my Commando/Featherbed set up, this was all done over 44+ years ago now and is still going strong.

Ashley

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I'm about to put my 71 commando back together again (found a barely tweeked rod causing oil bypass on lefthand cylinder) but am considering just using copper coat on a new copper gasket without going through the annealing process. Just wondering if you had any thoughts on this approach...rwanz

rwanz said:

I'm about to put my 71 commando back together again (found a barely tweeked rod causing oil bypass on lefthand cylinder) but am considering just using copper coat on a new copper gasket without going through the annealing process. Just wondering if you had any thoughts on this approach...rwanz

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Anneal! Add Copper Coat is OK and meant for the application. Still put some RTV on the 5/16" studs sticking up from the cylinders. Norton copper head gaskets do not come annealed - shocked me - every Triumph copper head gasket I've ever bought was annealed.

I've never re-torqued a Triumph copper head gasket and gave up on Norton copper head gaskets as they often leak and when I've put on a new one unannealed, they have always leaked.

I'm sure others have had different experiences - I'm just stating mine

If you use glue on the head gasket, the next time you take the motor apart, you might needto use a chisel. To make the Commando engine faster using petrol as fuel, a fuel ijection system might be needed. I use methanol - the needle jet size in my motor is 0.1165 inch. I get it by making my own needle jets, using a mix of metric and number drills. I also use 6D Mikuni needles in my 34mm Mk2 Amal carbs. It is difficult even with methanol to get the jetting within the adjustment range of the needles. I would not race a Commando using petrol in a normal carburettor. A better way to go, might be Bob Rosenthal's method of using and oxygen meter to set the jetting, them move the ignition timing to get maximum torque on a dyno. Advancing the timing as a similar effect to leaning-off the jetting. I am always careful to avoid moving the timing because my adjustment is in the jetting. It is surprising how fast a Commando engine can be when jetted right. I have started to think about buying a programmable Boyer ignition system. To me, my Seeley 850 was never about winning races, it was about improvement. If I had been interested in winning races, I would have raced the T250 racer I built. A win on that was dead easy, but it made no sense to do it. The Commando 850 engine in the Seeley frame with a close ratio gearbox and disc brakes, is much more interesting.

When you ride a well-tuned two-stroke racing motorcycle, you are forced to feed the throttle on to ride it fast, - my Seeley 850 is like that. To get real speed out of a Commando engine it needs to be like that and then you need to raise the gearing to maximise use of the available torque. The motor with the heavy crank can rev without pulling - it is deceptive. With wide ratios, the Commando engine is useless - you cannot use it properly. All that is needed is 3 close ratios up high and a low first gear for clutch starts. The gap between 1st and 2nd is not a problem. I just got stupid and bought 6 gears. I wasn't thinking.
These days I have nowhere where I can test the bike, and it cannot be raced unless I do that. If I put it back together again, I would need to go on safari.

What is this bullshit about vibration ? A strong pulse at low revs IS NOT vibration. Vibration is when the size of the handle bars increases at 7000 RPM, and there is one big vibration.

I did not race or drink alcohol until I finished my first diploma at age 29 and began to live. I have built hot motorcycles since I was 15 years of age. While I was working, I was always studying part time. When I began racing, I was running a laboratory in an aircraft factory. After 2 years, I moved up two levels to a job in an Ordnance factory, where I had one of the first two minicomputers in Victoria. That made my T250 Suzuki faster. In my life, I have had about 10 career changes. The last job I had as a scientist was running a laboratory complex in a defence factory - it was interesting, but not really challenging. In my life, I have always had a project. My Seeley 850 really pleased me. I never believed it would ever be good enough to beat larger capacity four cylinder Japanese bikes.

1. Annealing copper head gaskets.

Finally got around to the copper gasket question in post #1. It’s a simple stress problem and the answer is -
Yes. The yield point can be reached at small surface irregularities to flatten them, and out-of-plane bends can be flattened.
No. The yield point of annealed copper cannot be reached over the entire gasket when tightening the head down.

2. Vibration is less at higher revs with higher balance

Yes and No.
Vibration on (parallel twin engines) is usually presented resolved into two. Components - vertical & horizontal, but of more importance is how the other components and the rider feels it.
My coffee has gone cold so I’ll stop here and continue later.

rwanz said:

I'm about to put my 71 commando back together again (found a barely tweeked rod causing oil bypass on lefthand cylinder) but am considering just using copper coat on a new copper gasket without going through the annealing process. Just wondering if you had any thoughts on this approach...rwanz

Click to expand...

It's easy to anneal a head gasket and using copper coat is what I always do when replacing a copper head gasket, just last time I forgot to do the annealing but did put the copper coat on, well that was 15 years ago and the head is still sealed tight and has only been retorqued after the first 500 miles, the motor has over 35k miles on it since then.
As I have always said maybe I have a freak 850 that is happy in my hands, I have had more problems with fiber head gaskets with blown out completely, the good thing with copper they might leak a little and retorquing stops the leak but when a fiber head gasket blows out completely head removal and renew is the only way to fix it, I have never had a copper head gasket ever blow out completely, in fact my head has only been removed 4 time in near 50 years of ownership and the first time to replace a completely blown fiber head gasket (that was in 1979) and have used copper head gaskets ever since and the last 3 times from work done to my motor.

Ashley