The ton plus 10, what could be the problem?

With a road bike, you are usually using a wide ratio gear box. With that, you wait while the crank winds up. If you have at least four gears close ratio, you ride the top of the torque curve. So you get to top speed more easily. But 110 MPH is pretty good for an old British bike. When you are at that speed, it takes a lot of horsepower to get more speed, because of the wind resistance. You would probably go faster if you fitted a fairing. But why would you bother ?

My 850;Mark 2A Norton is fitted with a 23 tooth gearbox sprocket and pulls good top end speeds I have had it at 110 MPH on a few occasions just recently My friend was riding it at 180 KPH I was following on his Yamaha R1 and that was the reading on his speedo The engine was built by a guy names John French ie Triplemiester would love to know what he did to the engine at this speed my friend said the engine was still picking up speed

There are two aspects - top speed and acceleration rate. You will probably get a higher top speed if you are prepared to wait forever. With a close ratio gearbox, you get there quicker, so the top speed is likely to be higher before you run out of road.

cjandme said:

CB750F SOHC, put the "big bore 828 kit" in it, balanced and bluprinted, Kerker header, mikuni smoothbore carbs with K&N filters and a big ole' oil cooler out front - no fairing and a tank full of beautiful blue racing gas. Did an impromptu speed run on the way to the texas world speedway with a few friends. At 125mph I backed off, although the bike was chompin' at the bit with still more left in it.

Click to expand...

Maybe. I have always found Japanese speedometers to be very optomistic. I once passed a Z900 that was going 135 mph. My smiths speedometer read 110. In 1969 I had a CL 350 Honda that would do 97 mph. I don't think so.

The stock Commando motor will get up to 116 mph if you have a long enough road to wind it out, have both fuel taps open, they get over the ton pretty easy but its getting the most out of them the hardest part, getting enough fuel to the motor is the biggest problem with winding them right out, the carbies just can't keep the fuel up to the motor quick enough.
But do a bit of work on the motor (hot cam, lots of port work etc) and bigger main jets if you keep the Amals and they will get a lot more out of them.
But the way things are today with speed cameras, more police on the road with every cop car and motorcycle with on board radar, the fun police have taken the fun out of pushing our bikes to their limits and here in Aussie land anything over 40ks of the speed limits and they take your bike or car off you for 30 days and keep them if caught doing it 3 times, bloody hoon laws all because the young ones are wiping themselfs out and taking others with them.

Ashley

A bike that's notorious for vibration with an asymetrical crankshaft that is known to flex is not a bike that I would "rev out" to find it's top speed. I've touched 100 mph a few times just to see if it would go there, but I didn't keep it there long. If I wanted to have a norton that would do high RPM's, I would build it with a strong crank, superlight pistons and a bigger displacement to put less flex on the crank. I'd try to push a taller gear with more HP, rather than stress out a poor design for high RPMS. (or just buy a hayabusa and go really fast)

I ride with GPS unit on the handlebars mounted between my clocks. My Speedo is accurate below 80 mph. Above 85 mph it floats well past the actual speed indicated on the GPS. Stories of street bikes doing 140 mph are probably experiencing some speedometer "float" among other things...

** When I had my honda '79 750F, I foolishly buried the needle down the long steep hill on the NYS thruway from the palisades parkway down to the intersection with rte 303. The hill is quite steep and probably 3 or 4 miles long. I think the speedo went to 135 mph. That bike was wicked fast for it's era. I used to cruise at 90+ mph on the Northway going from albany to plattsburg. Eventually, the combination of power, speed, and youthful stupidity caught up with me...

Going to radiused lifters with a cam that was designed for flat lifters has reduced your duration closer to a stock cam. A large port combat head with a combat cam pushes a norton towards race tune. Restoring the cam duration (if the valves aren't too big), temporarily removing the mufflers and temporarily replacing the aircleaner with velocity stacks should realize the full HP potential of your Combat and give you one hell of a top speed thrill. After that you'll have to figure out how to make it streetable without slowing it down.

When I first convered my 850 Commando motor to the Featherbed back in the early 80s my crank balanced at 72% fresh tight rebore, my cam built up and regrined to Combat specs, lots of head work mostly on the ports running stock valves and stronger springs, bigger main jets and running volocity stacks and open exhaust system I was out on a long straight run with a few quick down hill runs I was pulling well over 120 mph and still pulling hard winding it out when I went through a police radar trap, them days a cppoer would be sitting at the radar box and further down the road another copper be waiting to pull you over, the reading was 125 mph, but to my surprise the copper on the radar was a old bike cop who rode the old Triumph police speicals of the times and was truely impressed with my speed reading, he walked down to where they finaly pulled me over and we were talking for about a hour about what I have done to my Norton and other things, I was even more surpriesed when he told me to take off without a ticket but a warning to slow down.
I think because it was its first high speed run after it was run in, the motor is still the same to this day with a few more improvements over the years but not running volocity stacks as they didn't stay on long, well after the fire anyway, thats another story, but being older and more wiser high speed runs are no longer done but I still take it just over the ton every so often when I get the chance as well the Featherbed set up is a lot lighter than a Commando which helps.

Ashley

o0norton0o said:

A bike that's notorious for vibration with an asymetrical crankshaft that is known to flex is not a bike that I would "rev out" to find it's top speed. I've touched 100 mph a few times just to see if it would go there, but I didn't keep it there long. If I wanted to have a norton that would do high RPM's, I would build it with a strong crank, superlight pistons and a bigger displacement to put less flex on the crank. I'd try to push a taller gear with more HP, rather than stress out a poor design for high RPMS. (or just buy a hayabusa and go really fast)

I ride with GPS unit on the handlebars mounted between my clocks. My Speedo is accurate below 80 mph. Above 85 mph it floats well past the actual speed indicated on the GPS. Stories of street bikes doing 140 mph are probably experiencing some speedometer "float" among other things...

** When I had my honda '79 750F, I foolishly buried the needle down the long steep hill on the NYS thruway from the palisades parkway down to the intersection with rte 303. The hill is quite steep and probably 3 or 4 miles long. I think the speedo went to 135 mph. That bike was wicked fast for it's era. I used to cruise at 90+ mph on the Northway going from albany to plattsburg. Eventually, the combination of power, speed, and youthful stupidity caught up with me...

Click to expand...

The main reason that I persevered with my 500cc short stroked Triton for 12 years, was it was indestructible unless I revved it over 11000 RPM. I rode it a couple of times at Phillip Island. It was not fast coming out of corners, but at the ends of the straights, it was insanely fast. It went past other bikes coming up to corners as though they were standing still. Phillip Island is one place I with never ride my Seeley 850. The thought of that at the end of the front straight with the motor near peak revs, horrifies me. If it blows up on a short circuit, the crank might get me or it night not. But at extremely high speeds a blow-up would be extremely nasty.

Many years ago I had a 650 Triumph which had everything done to it. My mate and I rode it two-up down a very long straight but hilly road. We were absolutely flying when we went over a rise in the rode and it started to rattle. So we rode it home very carefully. When we pulled it apart, we found one of the crank journals had broken and was held together by about 3mm of steel.

Ashman

I have a story similar to yours - heading home one night I was just getting into an open country road where I started opening up the throttle. Two cop cars pulled me over.

The first thing they said was "do you know how fast you were going?"

The 2nd thing they said was "what kind of bike is that?"

It turned into a conversation and 20 minutes later they let me off with a warning.

jseng1 said:

Ashman

I have a story similar to yours - heading home one night I was just getting into an open country road where I started opening up the throttle. Two cop cars pulled me over.

The first thing they said was "do you know how fast you were going?"

The 2nd thing they said was "what kind of bike is that?"

It turned into a conversation and 20 minutes later they let me off with a warning.

Click to expand...

In the old days we seem to have got away with more things and be let off with stern warning, but these days its a bit harder to get away with anything, the cops are a lot younger, more female officers who are in charge and won't give a inch or all bike riders are hardarse bikies in their thinking as well a lot more pressure from the goverment to make more money for them in the gise of road safety and most older officers are forced to retire or put behind a desk.
Life on a bike was a lot more fun and easier on the back pocket back in the 70s, but these days everyone is out to get their share out of us.

Ashley

I just came back from Nova Scotia (on the ferry) and I can see why the bikers like it up there. Unending pavement and passing areas on the hills. We drove from Yarmouth to Sydney. About 8 hours and the traffic was as light as you would expect in that area. I could see doing over the ton a lot there, and there were few cops. But the Canadians are very friendly people and I'm not sure they would like the ton bikers, I didn't see any until we were on the way back in MA/CT where they drive like crazy. The Trans Canadian Highway is probably the same. Nice cool weather even in the Summer and lack of traffic. It's too bad I didn't have the Norton up there, it would have gone over well, I'm sure.

However I'm tired of driving lots of miles at my age.

As far as doing the ton, I think a 19 tooth sprocket would help. I didn't have any trouble on my S early on at least on the speedometer, but it's probably fudging it.

Dave , I’m sorry I didn’t know you were travelling in my area we could have met face to face .... my daughter Brenna lives in Sydney in winter and works in Ingonish through the better weather .... had an opportunity to meet Michael ( delagem ) and 2 of his sons this past Sunday , they were headed to Meat Cove CBI to sleep in tent on the cliffs all the way from Homer NY .... Michael was on 72 Combat , oldest son older racing Ducati 748 and middle son on Suzy cruiser , quite a sight seeing them heading down the road ... My wife and I shared a meal and bike stories with them before showing them the trailer park where Trailer Patk Boys used to be filmed .... anytime you or anyone on forum is headed to NS please feel free to make contact ...
Craig

pommie john said:

I made simple excel spreadsheet with a few formulae to work out speed vs RP< with various gearing. It's dead easy.

Engine RPM x primary ratio x rear ratio = rear wheel rpm :

Example
21/42 primary = 0.5
20/42 rear ratio = 0.476

7000rpm x 0.5 = 3500
3500x 0.476 = 1666

So the rear wheel is spinning at 1666 RPM

Our tyres are roughly 80" in circumference so we are doing 133280 inched per minute ( 1666x80 )

Another simple reduction gets us from inches per minute to miles per hour: 126MPH at 7000rpm

Once you enter the formulae into the spreadsheet you can change any parameter and see what happens when sprockets or tyres are changed.

Click to expand...

An improvement to your spreadsheet would be to input the distance your loaded tire makes for one revolution. This is easily done by sitting on the bike, having someone make a chalk mark on the tire and the pavement, then "walking" the bike, keeping your weight on it, until the chalk mark makes one revolution. Mark the pavement again and measure the distance between chalk marks.

Using the unloaded tire diameter can result in significant error on the high side.

Slick

Craig, Yeah, I didn't even think about contacting a Norton enthusiast for some reason. Wife was up there for a Border Terrier dog show. So we drive a week for about 15 minutes in the ring. I'm not into the dog thing and would have enjoyed meeting some enthusiasts in CA, I had a day in Halifax and several in Sydney. Weather was nice, but warm for them, in the 80's, pleasant for me. Nice people up there. Enjoyed some lobster and scallops and of course had to see the Puffins.

No worries Dave , maybe another chance some day .... early on when kids were small ,We had a pair of English Bull Terriers and we were sort of in the dog scene for awhile , the dogs were for the kids but really became part of family .... my daughter the Cape Brenton Chef runs a side fermentation business called “Punch & Jingles” in memory of the 2 Terriers .... still pretty hot for me here , hard to imagine I used to run power saw in deep woods in weather like this and think nothing of it , I did look forward to cool one after I was home though .... real glad you enjoyed your trip up here to our little Province .... lots of bikes on back roads and folks are fairly understanding with the “ton up” boys ... not many will talk to police for any reason ... something to do with our heritage and how our ancestors got here .... legend is my family was turfed from both Wales and Scotland for taking sheep ... they were starving .... I may get down your way once more before the end and will see if you around , always fun to trade bike stories
Craig

Craig, if you get in the DC/NOVA area give me a shout. It was a great trip despite the road time. It was like driving to Los Angeles from here, less the CAT ferry from Portland to Yarmouth and back which was nice. We have a spare room for any Norton enthusiast. We met several bikers near the Cabot trail before we went on the bird island boat and they were a pleasant bunch, mostly Harleys and triple tires of one sort or another. Never saw any Brit Iron unfortunately.