850 top end

acotrel · Jun 26, 2023

baz said:
6 horse's is a big loss in the mid range where I'm guessing most of us ride

It is absurd to do that with a commando motor. The theory is more revs gives more horsepower, but a gearbox is a torque converter, Wherever the power is developed in the rev range, it can be used. For fast cornering smooth power delivery is much more important than top end. You will never beat anyone down a straight with a Commando, if you are not faster than them in the preceding corner. - 'Torque wins races'.
I wonder how many guys race with the standard Commando gearbox ? - I did it only once. The bike simply would not go.

possm · Jun 26, 2023

Another thing to take into account is your conrods, I raced a supercharged 850 speedway sidecar in the late 70's- early 80's,
as i was still using stock rods i kept the rev limit to 6800- 7500 never thru a rod where as a couple of 810's revving above 8 had a few blow ups. yes my big ends needed re sizing at the end of the season!

baz · Jun 26, 2023

acotrel said:
It is absurd to do that with a commando motor. The theory is more revs gives more horsepower, but a gearbox is a torque converter, Wherever the power is developed in the rev range, it can be used. For fast cornering smooth power delivery is much more important than top end. You will never beat anyone down a straight with a Commando, if you are not faster than them in the preceding corner. - 'Torque wins races'.
I wonder how many guys race with the standard Commando gearbox ? - I did it only once. The bike simply would not go.

Al this part of the conversation was about 6hp lost in the midrange due to fitting a pw3 camshaft as opposed to a stock camshaft

Schwany · Jun 26, 2023

colin davie said:
Thank you all for your replies..... pretty much what i was thinking, i wonder if i did fit these sleeves with loctite how easy it would be to remove if no gain was made ... maybe overthinking it all ??

I'm thinking let Glen (worntorn) do his thing before making that install decision. They should be useful at some point going up a hill if the description of purpose is true.

I want to say they are not that hard to remove with the head off and valves removed but have never installed them because my port openings are only 31mm and work well for my use. However, someone else may have some experience installing and removing them for one reason or another.

Overthinking and Norton go hand in hand. It's all good.

worntorn · Jun 26, 2023

Last run up the hill I recorded the third gear results as well. Usually I just go in fourth gear which means revs are around 3900 at bottom and 4350 +- at the top.
Using third gear and the same 100 kmh starting speed at bottom yields 120 kmh at top , 10 kmh more than the speed at top of hill in fourth. The rpm range is around 4700 at the bottom and 5600 rpm at top, so getting close to the peak power rpm.
It will be good to do the two tests, one to show midrange effect, if any, and the other to show higher rpm effect.

Glen

Onder · Jun 27, 2023

There always seems to be three sets of circumstances: race bike, hot road bike and 'regler-just-a-rider' bike. Those circumstances are quite different. I think the JS page says "improved throttle response" which sounds to me like a standard road bike. It is tough to resist the 'more power' urge but, in time, you can see it makes the most sense for most of us!

Desmopower · Jun 27, 2023

possm said:
Another thing to take into account is your conrods, I raced a supercharged 850 speedway sidecar in the late 70's- early 80's,
as i was still using stock rods i kept the rev limit to 6800- 7500 never thru a rod where as a couple of 810's revving above 8 had a few blow ups. yes my big ends needed re sizing at the end of the season!

750 combat speedway sidecar - big hole in cases after 2 seasons but it did keep the multi's honest.

YING · Jun 27, 2023

worntorn said:
Once I'm healed up from the cow attack I'll do a before and after using the sleeves on dyno hill.

Glen

Glen,
I have never heard of a cow attack!What happened and I am glad you are getting better!Oh well,life on the farm.
Mike

robs ss · Jun 27, 2023

YING said:
Glen,
I have never heard of a cow attack!What happened and I am glad you are getting better!Oh well,life on the farm.
Mike

I had a situation in about 1980 riding my Suzuki GS850 shaftie 400km from my girlfriend's place to home early one Monday.
At the Marlborough range (about 130km north of Rockhampton) I came across a mob of Zebu (bit like Brahmans but worse tempered) on the road. No fencing on about 150km. I waited a bit before blowing the horn at them. Three of the bastards charged me. Only just managed a u-turn without getting hit.
Feel for you Glen (@worntorn )
Cheers

Sorry: WARNING, WARNING, DERAIL, DERAIL!!!!

worntorn · Jun 27, 2023

YING said:
Glen,
I have never heard of a cow attack!What happened and I am glad you are getting better!Oh well,life on the farm.
Mike

I was knocked unconscious then thrown around by a large Simmental beef cow. I came to about 100 feet from where she first attacked me. She was standing on top of me with both front feet on my chest. That doesn't seem possible as she weighs about 1800 pounds, heavy to the front, so roughly 1100 on me. The rib cage mostly held.

I came to and yelled which caused her to step off of me and leave.
I have lots of bruises, some broken ribs a separated shoulder and a torn rotator cuff.
Other than that I feel pretty good

Glen

acotrel · Jun 27, 2023

baz said:
Al this part of the conversation was about 6hp lost in the midrange due to fitting a pw3 camshaft as opposed to a stock camshaft

A standard Commando cam is hot enough already without going more radical. The reason a normal Commando is not ectremely fast is the gearbox and the crank balance factor. But would you really want a Commando to be very fast, for road use ?
There wass a video on here a few days ago which compared a Commando with a BMW. When the guy was on the Commando was giving it a squirt, he was then continually shutting it off.
I suspect the motor in my Seeley 850 is not much better than standard. However what is associated with it, makes it much faster than normal. With motorcycles, most hot-up stuff is bullshit - the gearbox makes the biggest difference. A Manx 4 speed cluster costs about $700, and the Commando first gear fits.

acotrel · Jun 27, 2023

If you know anything about camshafts, compare the timings of a Commando 850 cam with those of a Triumph E3134 race cam.
Lift is not important - it is where the power band is that matters.

baz · Jun 27, 2023

acotrel said:
A standard Commando cam is hot enough already without going more radical. The reason a normal Commando is not ectremely fast is the gearbox and the crank balance factor. But would you really want a Commando to be very fast, for road use ?
There wass a video on here a few days ago which compared a Commando with a BMW. When the guy was on the Commando was giving it a squirt, he was then continually shutting it off.
I suspect the motor in my Seeley 850 is not much better than standard. However what is associated with it, makes it much faster than normal. With motorcycles, most hot-up stuff is bullshit - the gearbox makes the biggest difference. A Manx 4 speed cluster costs about $700, and the Commando first gear fits.

What camshaft do you have in your Seeley Al ?

acotrel · Jun 27, 2023

Onder said:
There always seems to be three sets of circumstances: race bike, hot road bike and 'regler-just-a-rider' bike. Those circumstances are quite different. I think the JS page says "improved throttle response" which sounds to me like a standard road bike. It is tough to resist the 'more power' urge but, in time, you can see it makes the most sense for most of us!

With most road bikes the taper on the needles in the carbs probably richen up too quick, to cater for heavy-handed people. With slow taper needles and more controlled throttle opening, the throttle response becomes much better.

acotrel · Jun 27, 2023

baz said:
What camshaft do you have in your Seeley Al ?

I do not know. I had it ground and simply asked for the best Norton grind. The timings are not much different from standard. It is probably the 650SS cam profile from the early 1960s. I run it 12 degrees ahead of normal Commando 850 timings. What it is, is probably irrelevant. When I had it ground, I knew it didn't matter what it was, I could get it to work. My cam sptocket has 3 keyways boached in at random. Adjusting the cam to suit the exhaust system is trial and error. It needs to be done on a race circuit.

I learned to race with this bike :

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850 top end

acotrel

possm

baz

Schwany

worntorn

Onder

Desmopower

YING

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robs ss

worntorn

acotrel

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baz

acotrel

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