How fast will she go?

Skyguyz,

If you're going for it you might as well go for it. Don't sit bolt upright, since a Commando positions the rider like a big sail in the wind and the air drag is ridiculous. Put your feet back on the passenger pegs, lay on the tank and try to crawl under the paint and logos, with your left hand get an underhand grip with a couple fingers on the left handlebar in behind the gauge, keeping your left elbow touching the tank. Run up to 70 mph, slide your asrse back and assume the position, roll it on, peak at the road from between the gauges, and see where you get in 30 seconds. You'll be delighted with the outcome. We’re eager to hear how you make out.

WZ507 said:

Skyguyz,

If you're going for it you might as well go for it. Don't sit bolt upright, since a Commando positions the rider like a big sail in the wind and the air drag is ridiculous. Put your feet back on the passenger pegs, lay on the tank and try to crawl under the paint and logos, with your left hand get an underhand grip with a couple fingers on the left handlebar in behind the gauge, keeping your left elbow touching the tank. Run up to 70 mph, slide your asrse back and assume the position, roll it on, peak at the road from between the gauges, and see where you get in 30 seconds. You'll be delighted with the outcome. We’re eager to hear how you make out.

Click to expand...

Wear tight cloths or none at all. Get rid of restrictions like turn signals and rearview mirrors. It won't matter if you see a cop coming in the mirror, it will be too late anyhow.

It doesn't matter how fast it will go as long as it is fast enough. It depends on the overall gearing and the internal gearbox ratios, how long the road is and whether it is straight or has a slope. Also whether you can get down out of the wind. The limiting factor is usually wind resistance, as you go faster the power needed for the next bit of speed increases exponentially. Rolling resistance also plays a part. On a race circuit the higher speeds achieved by bikes of equal power are dependent on how fast the rider gets around the corner into the straightaway and how early onto the gas, and the correct gearing and torque characteristics are thus essential. If I had your beautiful bike, I wouldn't even bother to try to find out how fast it would go because in a minute it would look like my dirty old Seeley racer. If you are looking for bragging rights, it will never be fast enough. It all becomes subject to the law of diminishing returns.

acotrel said:

It doesn't matter how fast it will go as long as it is fast enough.

Click to expand...

For sure, although I can understand why someone would want to know. But everyone of these 40+ year old bikes are a testimony and a piece of history. While most are just well maintained runners, some are resurrected and works of art, all deserving to be honored, cherished, and ridden.

Achieving a Ton is testimony that is will sure go beyond, but to what end. I am sure many reach a Ton THEN shift to forth.

I have reached 100 mph quite a few time on my bike but have also seen 140 on a 999 by the time I got to the end of the highway entrance ramp. It's all relative.

Now it is a matter of how quick I can get to 100. 80 seems common, 90 is often and beyond that is there but what's the point. Going through the gears and feeling the torque through the midrange is what it's all about for me.
Simply put, it's fast enough and quick enough.

It will be faster than you really want to go, if you think about it. I did it once, and that was enough, I think I was in my 20's and never worried about it again. I remember seeing 120 on the speedo, but I'm sure it reads high. 750 S with stock 930 carbs and 19 tooth sprocket. I95 between Beltsville and Columbia, MD very early one Sunday morning in the mid 70's, no traffic. I still remember it.

ashman said:

My stock 74 850 use to get 116 mph and no more with stock gearing and only got to 6,500 rpm, but only had my stock motor for 4 years before I built it to the Featherbed frame and a hot motor, after I built this bike up with the balanced motor, S2 cam and other work it would run freely and have been over 125 mph on a straight run, how do I know this, radar speed trap,(coppers) :roll: and it was still pulling.

Ashley

Click to expand...

Was testing some flatlside carbs at 3/4 throttle looking for a plug check to help determine needle position (twist grip marked at 1/4 1/2 & 3/4). Sitting bolt upright to help slow me down, was suprized to see it pull to 125 and still accellerating before I shut off. Not stock - all JS parts with JS0 (nearly stock) cam, some porting according to the race manual. Free breathing pipes. Probably pretty close to your ride.

by DogT » Thu May 08, 2014 5:58 pm
It will be faster than you really want to go, if you think about it. I did it once, and that was enough, I think I was in my 20's and never worried about it again. I remember seeing 120 on the speedo, but I'm sure it reads high. 750 S with stock 930 carbs and 19 tooth sprocket. I95 between Beltsville and Columbia, MD very early one Sunday morning in the mid 70's, no traffic. I still remember it.

Click to expand...

Yeah man > to a man admitting to illegal risky behavior but what does your memory linger on while still got a memory let alone desire to test top out. The ones that really want too can get em to go over 120 routinely. Even through Commands can get out horse powered the pull up to that point is about as good as it gets. I got too scared d/t the vibration and wind blast roar to ever let my P !! top out when I was 20 but told pulled at least 120 with HD 1%'rs it attracted. Oh I could out pull them up to about the ton when front would stay down on WOT then neck and neck to who knows how fast with bikes in both lanes in rural hwys. Always makes me feel like such and outlaw to ride real fast into an oncoming lane on purpose.

Ok fast how would ya go on an isolastic Commanod if you could go that fast? Grandpual invited me to Texas Mile but there is a handful of these event around and highly recommend one to see what state the cycle pilots are in picking up the time slip... What tires would ya trust past H rated skinnies? I think Peel upped her final drive ratio at some point as rear expanded the rpm dropped but mph bounced up a few more. Seems like a few 100 rpm difference but only had 1/2 mile to get er done and can really see road nor guages well tucked to max, then pop up to pull down some for the chicane which climbed thank goodness. The airport events usually have 1/2 too bleed off and hopefully some grass and brush further if slowing devices fail. On two different naked cycles I found 120 was my tuck in to lower drag but then had to be alert to grip tank or some bumps and humps would allow the air flow to lift my skinny bones out of the seat and feet off pegs! That sent spikes of nerve pain from groin up. Don't forget to let images of bikers bodies torn apart flash through for extra sharpened sense of thrill.

Skyguyz said:

Ok, So now that I have over 1000 miles on her, I can open her up and maybe join th "Ton up" club. but before I do….

How fast will a stock 1974 850 go? And how fast should a 75 850 with JS motorsports flat side carbs and CNW engine/tranny go?

Click to expand...

You must have found some nice weather and deserted roads outside of Las Vegas by now. How fast did it go and did you sit up or lie down?

I had my 75 mk3 up to 110mph. It was a good strong machine. Next day tranny gasket was spewing.

My 74 is not quite as strong, but I have not tried to push it since putting in +20 rings with a hone.

The ton on a commando , who cares! I would do it two up if requested by somebody female ,who smelt good looked good and had nails like talons! Otherwise give me a twisty road free of cow shit.

I found that my 71 Commando would struggle a bit when getting close to the ton. However, my preferred stretch of road was at a slight incline. On a slight downhill she was more willing. Problem is, the rider became less willing as she crept up to speed. I find my 1150 BMW much more willing and quicker to the mark with less pressure trying to throw one off the beast. Love that push button windshield. The Commando runs a 19 tooth sprocket and packs a heavy burden though. No turn indicators and one mirror. Things seem to get blurred as speed goes up and the helmet is trying to pull your head off. Of course at my age, most things are blurry anyway.

Your bike looks tremendous and I wish you well on your speed run. Please report back on the whole experience as it is surely quite exciting to do at any age. Ride safely.

My stock 73 850 with 22 tooth sprocket INDICATED a bit over 115 at WOT while living in NY (sea level). At it's current location, in Mexico's high desert and the Mexico City area, with the altitude between 6300-7400 ft, jetting adjusted for best performance at that altitude and a 20 tooth sprocket, I have never managed to get it to the ton. The speedo is quite accurate when compared with GPS so I'd say the 115 was probably pretty close to actual.

Skyguyz said:

Ok, So now that I have over 1000 miles on her, I can open her up and maybe join th "Ton up" club.

Click to expand...

How fast did it go?

hobot said:

All Commandos should top the ton by 15-20 mph if holding on long enough, especially 850's, for the waiting long enough part, which is more never wracking to pilot than engine and drive train. Definitely nip up fasteners from cradle to head before and *after* such an attempt as good test for adequate case venting breathing system oil sealing. A Commando pilot should be able to sit bolt up right past the ton on any Cdo and a few more mph if tucking down. W/o special features inside its too nerve wracking to me on engine innards to go above 90 mph much but still feels good to know ya can now and then.

Click to expand...

Welcome back Steve. Yes the speed limit here is on 100kph.

skyguyz. Me thinks the Norton mentioned above should have been belted along as soon as it had done only ten miles. Look for the thread about this that was around within the last month. I f I had done the engine rebuild and fitted it to the bike I would have given it a good run before giving it back to the owner. That way I would know it had been run in properly. The reason why new rings have slight grooves in them is so they can wear into the bore shape " QUICKLY "!!!!!!!!!!!!!!!! And that is one of the reasons why it should be done quickly and at decent revs and loads. Do not ever nurse these things or you may suffer from excessive crank case compressions, the cause of all oil leaks.
regards, Dereck

I like the thread starter have faster modern machines to scratch the speed itch. I never had mine up to the ton but often thought about it until this thread. Yesterday it was showing a steady 70mph at 4K rpm so I dont think it has enough to get all the way to 100mph without changing gearing or finding a big hill.

Yesterday it was showing a steady 70mph at 4K rpm so I dont think it has enough to get all the way to 100mph without changing gearing or finding a big hill.

Click to expand...

70mph at 4000rpm is normal for about a 20-21 tooth countershaft sprocket

your Commando should continue to pull strongly to right around 100mph

then top out at around 108

Faster than the unpiped purple terror in all respects .



Max. Hp / rpms & gearing dependant , also baffled exhale things could knock it back .

' One ' would run 23 or 24 T on the trans , if this was what ' one ' was after .

Should hold the front end off through first & snatch it in 2nd into 3rd , to keep up with a good Bonneville .
Though faster with the front within 2 inches or the deck . Lauches arnt as easy as with the old cork friction plates .

Winding it out fairly far ( 6500 ) through 2nd & third keeps / gets it on the boil . quite differant characteristics
through roll on and induction & exhaust ' in phase ' w o t & temperatures up ( temperature stabilised & in pipes )

Any old cow should do 120 appropriately geared , with your eyebrows just above the tank paint .

Some people are a bit wider than 10 stone though , and require slimming or fitting to suit , aproaching the sound barrier .

1up3down said:

Yesterday it was showing a steady 70mph at 4K rpm so I dont think it has enough to get all the way to 100mph without changing gearing or finding a big hill.

Click to expand...

70mph at 4000rpm is normal for about a 20-21 tooth countershaft sprocket

your Commando should continue to pull strongly to right around 100mph

then top out at around 108

Click to expand...

I'm going to give it a shot next time conditions are suitable and see what happens

speirmoor said:

1up3down said:

Yesterday it was showing a steady 70mph at 4K rpm so I dont think it has enough to get all the way to 100mph without changing gearing or finding a big hill.

Click to expand...

70mph at 4000rpm is normal for about a 20-21 tooth countershaft sprocket

your Commando should continue to pull strongly to right around 100mph

then top out at around 108

Click to expand...

I'm going to give it a shot next time conditions are suitable and see what happens

Click to expand...

Never had any of my two over 90ish on the clock (refurbished and new drive)but I would top them out if I had to, not out on my own for a run. It's a better experience and a better buzz if you have a reason, not that doing it for fun isn't a good reason, but if your going to destroy something you need someone there to see you making an ass of yourself.

I don't know how fast your bike will go but that is one very beautiful bike you've got there. Love the paint scheme.......Skip