Simplicity of Commando vs Other Brit Bikes? (2017)

baz said:

Yep there's no need to split the cases on a triumph to change gearbox bearings

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Same with big BSA twins. Gearbox comes out the side.

worntorn said:

My unit construction experience is mainly with 60s and 70s Japanese bikes.
Would you renew Triumph trans bearings without splitting cases?

Glen

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That's the advantage of the British engines being vertically split. You can go in the side. The disadvantage is they tend to leak from those vertical splits...

" The disadvantage is they tend to leak from those vertical splits... "

Thats what stops them Rusting .

Must admit , in the olde days youd find compasture and dead rats under the odd unit triumph , and all other sorts of grunge up in the cavities under it ,along with smashed chain top guides, that bit in the top of the crank case .

As for ' touring speed ' The 61 tweaked bBonnie would manadge 90 . Comfortable some days , strained others .
The commando , also tweaked , was 80 sweat spot , 100 easy , would sit on 100 - 110 . British Imperial thingos .

Both had raised gearing . 23 T on Knorton . Id think the 22 a ideal compromise unless atrophied in the city .

But of course. Not many Nortons came 5 speed stock .

The P U ran 24 T primary , std whatevers aft . 17.6 mph per 1000 ??? rings a bell . 4 speed. Std Ratios .
Tuned Pipes and the pear flank ( Thruxton Spec. ) crank got it lively . Before the headers were cut down , you could fall in holes between gears . Particularly two up going up hill . 90 in third to Top , no pick up left.

With the pipes cut down , itd run past ' the Ton ' .

Quite Francisly , I think any twin carb pommy bike thats not geared for past 1000 mph in third , isnt set up right , at all .

Pee Ess ,

The pre units had a 25 T engine Sprocket listed . In future Id use that. If a Real Motorcyle . rather than a relic .

A ' Wide Ratio ' ( about stock with a new first ) FIVE SPEED in a Commando , would enable ' Continetal ' motorway use
without the difficulties of a high first gear ( eqivalent of 2nd ) with the tall 22/23 T sprocket .
Harsh on the clutch , and awkward uphill loaded on mown grass lawns otherwise .

I think you have to consider modern driving conditions when you gear the bike. If you live in the far west USA or in the Vaterland the century mark
is something to consider. But for the rest of us you push past 80mph regularly you will attract the attention of The Authorities. If you live in the hill
country or you do a lot of two up riding then again lots of teeth on the gearbox sprocket means you wont be in high gear all the time.

I geared up a T160 once on the advice of an expert, the idea being to give it a relaxed rpm at high cruising speeds.

But the motor didn’t really have the grunt to accelerate without changing down one or two cogs. The upshot being that on most A road rides I rarely got out of fourth, as it would still accelerate, or only need knocking down one cog. In top, I had to knock it down two cogs and risk missing my ‘window’.

I rode it John O Groats to Lands End once, avoiding all motorways, with a mate on a modern Speed Triple, we we pressing on a bit and I hardly ever got into 5th.

Kinda defeated the whole objective really !

Yes I agree, a T160 should only be geared up if the engine capacity is increased. I run 19/47 on the 990 and it's just about perfect.
sam

Like many I have had Brit iron since birth ,Triumph tiger 750 made the best back lane racer, easy to work on unless you put the pushrod rubbers in wrong . very easy to tune plentiful for parts. I had a bored and stroked A65 by far the fastest and easiest to work on, joy to rebuild the gearbox. Then comes my commando somewhere in between to work on , but gives by far the biggest smile .to be honest owning a Brit twin keeps the cobwebs of my spanners ,and is all part of the experience or character building I call it when things don't go right.

“Character building”...

Oh how I’ve used that phrase over the years.

My missus just rolls her eyes at me these days when I say it.

She knows that what it really means is one of the bikes has disembowelled itself and gonna cost another small fortune to put right...

With a Commando on a race track, the American close ratio gearbox is perfect everywhere except off a clutch start. With a road bike, you would have a similar problem in slow traffic. The top three gears of the American racing gearbox along with a standard first gear might be adequate for a road bike. The bigger step between first and second gears would not really be a problem, once you get used to it. The set of American close ratio gears costs about $700, compared with about $5000 for a five speed box. If most of your riding was on freeways, you could simply raise the overall gearing, by reducing the size of the rear sprocket. If you really want to get a Commando going, those top three gears need to be very close and evenly spaced, but you still need to be able to ride the bike slowly when needs be.

With the top three gears very close, it only takes a quick blip of the throttle and you change down half a gear with almost no drop of revs. So when you pass somebody, it is almost instantaneous. - With the closer gears, you don't need to pull in the clutch, open the throttle and wait for the revs to rise before you change down. With the heavy Commando crank everything happens very slowly when you do that.
In the past different guys have told me 'you don't need a close ratio gearbox, if you have a torquey motor'. However most of them had never used a close ratio gearbox. Even in Japanese two strokes, closer gears make a big difference. That standard Triumph 5 speed gearbox a lot of historic guys use is better than a standard 4 speed, but it would be even better with Phil Pick's two pairs of gears which move 2nd and 3rd gear closer and up towards 4th.

This has been a great discussion. Somehow it pretty much stayed on subject and didn't morph into an oil or tire thread. Trying to arrive at which one is best, simplest, or most desirable is like trying to figure out which of the Three Stooges is the smartest. Go with what you like the looks of best. You'll never go wrong if your buying or collecting decisions comes from the heart. Nyuk, Nyuk, Nyuk!

I think what I learned is that I need a bigger engine. No replacement for displacement and all that...

With motorcycle engines, bigger is not necessarily better. It just makes life easier. With a race bike you don't have to ride so hard and concentrate so much if you have a big motor. But riding a small capacity bike in races against bigger bikes in races teaches you to ride well. I did that for 12 years and these days when I ride a bike of similar capacity to others in a race, I am usually faster - even when I am down on power. On a tight race circuit, a good guy on a Ducati or Aermacchi 350 can give a lot of guys on much bigger bikes a scare. The problem with a lot of smaller bikes is they often don't have the required gearbox. You cannot expect a small capacity bike to get mobile if it has a wide ratio gearbox. Six speeds close ratio are essential.

I once met Eric Hinton at an historic meeting, He owns the bikes that Harry Hinton had in Europe in the late 1950s. One of them is the Rennfox NSU 350. He has fitted a Suzuki 6 speed gearbox into it by machining up two gearbox end plates. He put somebody on it in a race, but was still disappointed. It has potential.

Interesting discussion on gearbox. I've had an RD350 with a close ratio 6 speed. On the track or in very tight twisties, it was terrific - you could keep it on the boil and reel in guys on bigger bikes. But it was a lot of work to ride it at that level. On the other end, I've got a BMW R75/5 with a 4-speed gearbox that shifts like a tractor. It's my favorite naked sport tourer, because it also pulls like a tractor. I'm not trying to set any speed records, I'm just riding the torque around the NC mountains in a semi-spirited way, and cruising at highway speeds to get there. No fuss, no missed shifts, and I don't have to think about it much.

My 73 Tiger was a great bike in the twisties and the gravel, and a very forgiving bike to ride and work on. First street bike I really felt comfortable spinning the rear and backing it into the corner, would just hook up and roll out every time. I had to split the cases to clean up a blown piston, and the engine was fantastic, with cheap parts from tons of places. Compared to the UJM bikes I'd worked on, it was like the little kid version of Legos, everything was big and obvious. And the transmission is still my favorite of any bike I've worked on. I took apart and re-assembled the gears about 4 times just for the fun of it, and I've never had a better shifting vintage bike. The routine maintenance stuff on the Tiger was all fairly obvious and common to most vintage bikes, which made for fewer mistakes. I really wish it was less miserable at highway speed, and that the OIF wasn't so visually unappealing to me.

By comparision, the Norton is more fiddly, with more stuff packed into the same space and more attention to detail needed to avoid expensive mistakes. It demands in-depth expertise on various idiosyncrasies like isolastics and head steadies and swingarm oil. It's far more mannered at speed, it handles well, it's an all-day bike you won't hate by the end, it looks absolutely stunning, but imho, it could be a challenging and frustrating first Brit bike.

If you read one of the latest Motorcycle Classics magazines, there is an article about the RD400 Yamaha, which has the same internal gear ratios as the TZ350 racer. It mentions, that when changing up through the box, the tachometer needles drops less and the motor has less tendency to bog down. I never thought that my Commando motor was bogging down, but that is probably what was happening when I tried to use the wide ratio box for racing. All I know is that when I fitted the close ratio 4 speed box, the bike performed radically better once it was mobile. With a Commando motor, high overall gearing with a close ratio box, is a very good way to go. When I raced my 500cc short stroke Triton, I always used a 4 speed Triumph close box. After I had sold it, I rode it again when it had a 5 speed Triumph box. It was actually better, but it desperately needed 6 gears. With four gears, you chose where you were going to lose races. Gear it low and it comes out of corners fast must slows down too much towards the ends of the straights - gear it high and the reverse happens - slow out of corners, but it keeps going faster towards the ends of the straights.

One of my close friends' son races an RD350 in historic races. I gave him a complete RD400 bottom end. I don't know if he has used the gearbox from it, yet. On the RD/TZ forums, a lot of racing guys seem to use Banshee gearboxes.

I found my Seeley Commando was much easier to get going fast than any early Triumph. The motor is extremely responsive to tuning and it loves methanol.

Bob Z. said:

You might as well order the Commando specific clutch diaphragm spring compressor now.

It's a must have tool.

And welcome!

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I've done a Commando clutch without that tool. A bolt like the tool has, a couple of nuts, a drilled piecre of bar of angle, and a short piece of pipe. Nothing to it.