My Combat broke on Saturday.

swooshdave · Sep 5, 2011

Hortons Norton said:
I wonder if anyone has hit a deer at those speeds? :shock:

Only once.

AussieCombat · Sep 5, 2011

Good stuff PV. If you've got it flaunt it. Occasionally.
Here's what "Cycleserv" 1972 had to say.
Primary drive... 26 tooth engine sprocket, 57 tooth clutch sprocket, = Ratio 2.19:1
Final drive... 42 tooth rear wheel sprocket.
Gear box sprocket... 19 teeth = Fourth gear ratio 4.48:1. OR 108 mph at 7,000 revs. (174kph)
20. 4.60:1. 114 (184)
21. 4.38:1 119 (191)
22 not listed. 124 ? (199.776) ?
I run a 22 tooth, and she slips up to 6,000 in top no worries.
After that... Don't care.
AC.

Matt Spencer · Sep 6, 2011

Later 850s ran the 22, which seems like a good idea .

Id thought 7.000 was about 116 on 19 T & 121 on 21 T.

& about 115 in third with 23 T . near enough.
The older tyres ' flung ' a little at high speed .
' grew ' hence no bolts protrudeing inside guards .
anyway all the variables ( slip etc ) evened out .

Going to a open day at a Race Tracks an eye opener. Its twice as wide , with nothing comeing the other way .
and it takes a bit of getting used to useing ' all ; the road . Brakeing points etc are challengeing too . take it quitely / step by step .

Also gives you a new perspective on road rideing , The mobile obstical course / chicane / tin box derby .

grandpaul · Sep 6, 2011

I guess I take it for granted here in Texas with W I D E O P E N S P A C E S, I do the ton almost every time I'm out and about, there are even a few spots around town with long, light traffic stretches...

Still, it's a good milestone, and if your bike holds up, a confidence builder. ESPECIALLY if it's a "built" Commando; seems they like to blow up crankshafts when you start adding significant horsepower.

pete.v · Sep 6, 2011

AussieCombat said:
Good stuff PV. If you've got it flaunt it. Occasionally.
Here's what "Cycleserv" 1972 had to say.
Primary drive... 26 tooth engine sprocket, 57 tooth clutch sprocket, = Ratio 2.19:1
Final drive... 42 tooth rear wheel sprocket.
Gear box sprocket... 19 teeth = Fourth gear ratio 4.48:1. OR 108 mph at 7,000 revs. (174kph)
20. 4.60:1. 114 (184)
21. 4.38:1 119 (191)
22 not listed. 124 ? (199.776) ?
I run a 22 tooth, and she slips up to 6,000 in top no worries.
After that... Don't care.
AC.

How about a 28 engine and a 55 clutch hub = 1.96:1 with a 20 gearbox sprocket?

This is the RGM ratio.

pete.v · Sep 6, 2011

highdesert said:
I have a book that compiles all the motorcycle magazine's road tests of Commandos through the years.

The tested, certified no BS top speed runs were all around 115mph, only the Production Racer could pull 125.

These were all box stock bikes, as sold to the public, but with magazine "professional" road testers doing the riding.

They did not go by visualizing the speedometer, they used speed guns, sea level, little or no wind.

Yes, these Norton are sooooo by the book aren't they. There is nothing on my bike that is original except for maybe the crank but I cannot confirm that either. This is a Combat spec bike with a bit more cam, flat side 32mm carbs and 1 1/2 exhaust. I don't know exactly what the Production Racers had, but I can't be far off. FWIW the speedo just came back from Nisongers with a fresh calibration.

That being said, I am not trying to confirm or deny anything other than the fact that i have had some personal success. With all the problems and trials that seem to overtake the forum, isn't it nice to know that these units can actually do what we hope they could?

DonOR · Sep 6, 2011

AussieCombat said:
Good stuff PV. If you've got it flaunt it. Occasionally.
Here's what "Cycleserv" 1972 had to say.
Primary drive... 26 tooth engine sprocket, 57 tooth clutch sprocket, = Ratio 2.19:1
Final drive... 42 tooth rear wheel sprocket.
Gear box sprocket... 19 teeth = Fourth gear ratio 4.48:1. OR 108 mph at 7,000 revs. (174kph)
20. 4.60:1. 114 (184)
21. 4.38:1 119 (191)
22 not listed. 124 ? (199.776) ?
I run a 22 tooth, and she slips up to 6,000 in top no worries.
After that... Don't care.
AC.

That sounds like things here too, Aussie. last time I "had to try for a ton", the needle just crossed 100 at nearly 6800, with my 19T.
After that, enuf for me... I'm mid 50's, most the roads around here are unsuitable. and at 330 kg, I'm almost flyin' off the seat with every bump over 70mph, my preferred highway speed. cheers, Don

swooshdave · Sep 6, 2011

330 kg? Is that bike + rider? You might need stiffer springs if you weigh 150kg.

nortriubuell · Sep 6, 2011

I like the ton on occasion here in Ohio pv, but "Ohio Hwy Patrol" are anywhere and everywhere. And ... MUST be on constant lookout. Done with my Buell and son's Yammy R6 regular ... but proly' poop my pants on commando yes sireee ....

Anyway, Kudos and my hat's off to ya pv !!! :mrgreen:

DonOR · Sep 6, 2011

swooshdave said:
330 kg? Is that bike + rider? You might need stiffer springs if you weigh 150kg.

hehe.... wrong numbers there... I'm 67kg, buck naked (and ugly too!)

Fullauto · Sep 6, 2011

pvisseriii said:
DogT said:

I did that back around 73 or so on 95 North from Beltsville going towards Baltimore one Sunday morning early. Just let it go flat out in 4th until it stopped climbing. As I remember it quit at about 120 on the speedo, but I have no idea what the real speed was, but it never got to 7K. Scared the bejesus out of me and never did it again. I guess we all have to do it.

Congrats too.

Dave
69S

Click to expand...

I brought it to redline earlier in the season in second gear to feel the upper end effects of the cam and carb. AWESOME! I feel 125 mph is easily attainable. 70 mph @ 5600 rpm = 125 mph @ 7000 rpm

Err, don't think so. With a 19 tooth sprocket you'd be doing about 4100 revs at 70 mph and about 7000 rpm at 119 mph.

DogT · Sep 6, 2011

Fullauto said:
Err, don't think so. With a 19 tooth sprocket you'd be doing about 4100 revs at 70 mph and about 7000 rpm at 119 mph.

I'm not sure what pv is running for a sprocket and primary belt. So he may very well be able to go well over the ton with his hyped up bike. I suppose I was doing somewhere near 100mph with my 69S close to 7K back in 73, but I doubt if I'll be doing it again unless I have the death wish.

Keep up the good work, guys.

Dave
69S

pete.v · Sep 6, 2011

Fullauto said:
pvisseriii said:

DogT said:

I did that back around 73 or so on 95 North from Beltsville going towards Baltimore one Sunday morning early. Just let it go flat out in 4th until it stopped climbing. As I remember it quit at about 120 on the speedo, but I have no idea what the real speed was, but it never got to 7K. Scared the bejesus out of me and never did it again. I guess we all have to do it.

Congrats too.

Dave
69S

Click to expand...

I brought it to redline earlier in the season in second gear to feel the upper end effects of the cam and carb. AWESOME! I feel 125 mph is easily attainable. 70 mph @ 5600 rpm = 125 mph @ 7000 rpm

Click to expand...

Err, don't think so. With a 19 tooth sprocket you'd be doing about 4100 revs at 70 mph and about 7000 rpm at 119 mph.

ERR, Fullauto this is what I am running,
28 engine and a 55 clutch hub = 1.96:1 with a 20 gearbox sprocket. Re-calculate. Again the numbers are 71mph @ 4000rpm. 100mph @ 5650 rpm.

Guido · Sep 7, 2011

Back in my twenties I did 112 mph on my 73 dunstall. It was scary.

Fullauto · Sep 7, 2011

Dave
69S[/quote]
I brought it to redline earlier in the season in second gear to feel the upper end effects of the cam and carb. AWESOME! I feel 125 mph is easily attainable. 70 mph @ 5600 rpm = 125 mph @ 7000 rpm[/quote]

Err, don't think so. With a 19 tooth sprocket you'd be doing about 4100 revs at 70 mph and about 7000 rpm at 119 mph.[/quote]
ERR, Fullauto this is what I am running,
28 engine and a 55 clutch hub = 1.96:1 with a 20 gearbox sprocket. Re-calculate. Again the numbers are 71mph @ 4000rpm. 100mph @ 5650 rpm.[/quote]

Sorry, assumed we were talking standard setup.

kingdaddyo · Sep 7, 2011

A friend of mine had a 1971 Honda 750 four cylinder and the two of us were riding it in the Spring of 1972. We took off on the highway and the bike hit 110 mph in no time. I remember the feeling of getting strangled by the helmet chin strap and was not feeling all warm and fuzzy about the experience. I prefer to lope along slowly these days without passengers in areas with little to no traffic. I have no interest in the crotch rockets or exceeding 100 mph again. Once was truly enough for me.

Hobot · Sep 7, 2011

Postby frankdamp » Wed Dec 22, 2010 11:11 am
During prototype high-speed endurance testing at the Motor Industries Research Association banked tri-oval, we would run between 100 and 110 mph for 10 hours a day, including fuel stops and chain tightening exercises (we had the 1/4" chain initially). The two riders switched rides every time we gassed up. At one time we were running two bikes with three riders switching off between them.

We did have one spectacular engine destruction when the chain broke at full throttle on the top of the bankng. Luckily, the engine bits were mainly contained within the case and only the chain was left on the track. We later were able to find it and determine that the split liknk had failed.

It really got interesting for the rider (not me that day) when the Aston Martin that was on the track with us and running around 160, started catching up rather quickly!

Hobot · Sep 7, 2011

Postby Rohan » Wed Dec 22, 2010 2:16 pm
That factory "blueprinted" 850 that did the 142 mph was on an airstrip, and with different gearing did a 12.1 sec 1/4 mile. (Anything that can do 140 over a quarter has a LOT of mumbo ?). It had a 1/2 fairing on it for the 142 mph airstrip run ? (not sure about this bit)

The Factory put out tuning sheets specifying was was needed for this - the sheets were called Stage 1 and Stage II for an 850.
A 4S cam was at the heart of it.

A magazine article on the engine build (in Motorcycle Mechanics) mentioned that Dave Rawlings and his crew had access to all the factory parts - and could hunt for a pair of perfectly matched rods (weights, lengths etc), 4 identical cam followers, all cam lobes with identical degrees, etc etc etc.

Hobot · Sep 7, 2011

Postby Seeley920 » Fri Dec 31, 2010 10:11 am

daveh wrote:I found a test of a Ducati Monster 620 (in 2002) to compare with a standard Commando — both of which have similar power outputs and are unfaired.

http://www.mcnews.com/mcn/model_eval/Du ... 20ie_2.pdf

It produced 54 hp, as dyno tested. It achieved a quarter mile time of 12.52 secs and a terminal speed of 104.24 mph, very similar to the 750 Commando tested by Cycle in 1973 (see my earlier post). The top speed was measured at 116 mph. I'd say anything above this on a Commando would mean it had been tweaked...

Funny you should say that.........when one of the magazines was doing a test of a 750 commando they only got about 105mph from it. They took the head off, brought it to Jim Boughen who tidied up the porting, and put the head back on. They told the magazine that the bike had some electrical problem.....and the next day it went through the speed trap at 123 mph!!! some electrical problem eh ??

Hobot · Sep 7, 2011

Bike magazine tested a Trident T160 and a Commando 850 Mark 3 in 1975 and were amazed at the speed trap figures for the Trident — 126 mph!! They quoted a bhp figure of 58 for both bikes, although these were almost certainly not measured at the rear wheel but were factory-quoted figures. The Commando Mark 3 managed 111 mph. Both machines had annular discharge silencers.

My Combat broke on Saturday.

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