Date: Fri, 19 Jun 1998 08:42:57 +0100 (BST)
From: Peter Aslan
Fellow members.
Whilst trying to get to the bottom of my Flat out performance problem, (now believed to be a combination of Carb and Choke trouble) I was doing a bit of research into the top speed of the Old Commando.
Looking at all the bike reviews I could find, the differences were amazing.
The original 750, (non Combat) was good on some reviews for up to 120 Mph.
The Norvil Yellow peril was capable of 130.
The Combat was good for up to 126.
The fist 850 were good for anything between 110 and 115.
The last 850 Mk 3's were, reportedly incapable of topping the ton.
While I assume some of the above figures were obtained using bikes supplied specificially by Norton, and therefore prepaired for Motorcycle Press evaluation, (i.e. Hotted up a bit), there's still a wide margin.
That not to say that we, the current owners, probably own bikes with Speedo's which are inacurate to say the least.
My feeling is that a standard 850 Mk 1 or 2 should be capable of at least 105, and probably 110. I'm sure my bike used to run to these numbers before the carbs were changed.
Any Comment.
Regards,
Peter Aslan (aka Captain Norton). Louden Quill Award.
Date: Fri, 19 Jun 1998 12:14:57 +0200
From: Espen Olsen
At 08:42 19.06.98 +0100, Peter Aslan wrote:
>The Combat was good for up to 126.
>Any Comment.
I've seen an indicated 120 mph on my '72 Combat at which point I didn't dare to push it any further. I don't know how accurate the speedo is at those speeds but calibrated against a police radar (yeah, right) it was fairly accurate up to 105 km/h (65mph).
My bike is equipped with a SU carb, no compression plate, original bore and pistons. It pings somewhat when riding uphill at low revs.
--
Espen Olsen
LA6MGA/LA1K, SST#5, DoD#7962, <*>
'57 Triumph 5T, '72 Norton Commando 750 Combat, fast new computer,
NOK 40,- In theory, there's no difference between theory and practice,
but in practice, there is.
Date: Sat, 20 Jun 1998 15:58:34 +0000
From: Eric Goforth
Peter Aslan wrote:
> Fellow members.
>
> Whilst trying to get to the bottom of my Flat out performance problem,
> (now believed to be a combination of Carb and Choke trouble) I was
doing
> a bit of research into the top speed of the Old Commando.
[Snip]
I had my '73 850 to an indicated 110+ before I rebuilt it, I think that it could have done another 2 to 5 mph with the chin on the tank, etc. It's anybody's guess as to how accurate the speedo was at that speed. Since having the speedo rebuilt, it reads about 7 mph low at an indicated seventy according to stopwatch times over a measured mile on the Interstate highway. I think that it was more accurate before. I've put in a Megacycle street/race cam, so I'd guess that it should be capable of close to 120 now. Since rebuilding it, I've had it to just under an indicated 100 which I think is closer to 105 to 110, my tach. was reading something like 6200 rpm.
With a 21T countershaft sprocket, which my bike has, a Commando would reach theoretically reach 119 mph at 7000 rpm. With a 19T countershaft sprocket a Commando will pull 111 at 7000 rpm, if I recall correctly. The 20T countershaft sprocket would pull about 115. I'm looking at a couple tests an early 750's with 19T countershaft sprockets doing 114.5 and 116.4 mph and revving to 7250 and 7380 in top gear. So with a 21T countershaft sprocket maybe these would have gone 120.
I think that the early 750's were geared low to make their 1/4 mile times more impressive. Most drag strip times in magazines for 750's seem to be around 13 sec. flat at around 100+ mph. I've seen several tests of early 850's pulling similar times in the quarter mile with taller gearing and giving a top speed of 116 (not overrevving), maybe they were tweaked. I also have a Cycle Australia test of an early 850 that would only do 14.00 sec in the 1/4 mile and topped out at 100 mph, so there seems to be a lot of variability there. The Cycle Australia bike has Interstate mufflers (not beancans) and the early type air filter, so maybe their bike was sick. The MkII's seem a little slower, I think that it's because the air filter, exhaust were more restrictive and '74s also had smaller intake ports. The MkIII were also heavier due to the electric start.
The whole weight thing got me curious, since I've also seen a great variety of curb weights in these magazine, anywhere from under 400 for fastbacks to over 500 pounds for MkIII Interstates. I weighed my bike using the bathroom scale with one tire on the scale and one wheel on a 2 x 6 board. I got 202 lbs for the front wheel and 226 for the back wheel, so 429 lbs total for a '73 850 roadster with a 1/2 tankful of gas. The bike has no turn signals and has a Corbin seat which is probably a couple pounds lighter than the stock seat. I believe that the driver and pillion rearsets probably weigh about the same or less as the original pegs. The toolkit is probably a pound or two heaver than the one that would have come with the bike.