Your opinion about a six speed gearbox on the sunburst

Ay, and the faster you go the blinder they get

storm42 said:

Ay, and the faster you go the blinder they get

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That is part of the problem. Track inspections for licensing purposes, usually involve a few guys walking around the circuit. Race circuits look totally different as you go faster. Some of the guys who do the licensing, have never raced motorcycles. So what can look OK to them, might not be. Car guys do not think like motorcycle riders.

There are three places on Winton Motor Raceway where you are facing a wall. If you see airbags, you just don't stick your neck out. Anywhere else, it is a safe as houses. Can't say the same for most other Australian circuits.
On the Mount Gambier circuit, there is one blind corner, but with plenty of room to go bush if they are all over the road. The one at Phillip Island is super scary.

Well, Zolder in Belgium has a fast blind lefthander bang on top of a hill, with a sharp right/left chicane just downhill from it. Exciting and easy in a car, much less so on a bike...

One of the joys in riding an old bike is the 4 speed box.
The sole irritation of riding a modern is the six speed box, even though it works well..
I guess I'm lazy!

Glen

I get you Glen, SOMETIMES there is something very satisfying about using an engine with a broad spread of power, and actually using that broad spread rather than just snick, snick, snick through the gears.

But that big difference in revs can be a pain on a bike used on the track, when changing down whilst barrelling into a hairpin for example.

Different horses for different courses I guess.

I think a modern five or six speed box is easier because there is less jump rpm jump betwixt the gears.

worntorn said:

This is true, track riding and road riding are quite different.
Yves does both and there is really nothing wrong with the six speed on the road, while it will have an advantage on some tracks.

My sportbike actually needs six gears to make the most of its engine.
The Thruxton R would be quite fine with 4 but the consumer says six is better.

The silliest one might be my 1360 with the five speed. It seems like each gear is only good for a couple of seconds of hard acceleration before rev limiting.

Glen

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Hi Glen,
I dont ride on a track sins 1981
Yves

Just noticed Worntorn said:

'My sportbike actually needs six gears to make the most of its engine.
The Thruxton R would be quite fine with 4 but the consumer says six is better.'

I wonder if that is true about consumer opinion?

Or is it more likely that Triumph benefits with parts commonality with other bikes in it's range?

Bear in mind I know nothing about their current range, and comparatively little about any Triumph motorcycle product since 1900!

Triumph asked owners what they wanted to see on the new series Bonnies.
A sixth gear was near the top of the list. It seems the old low power air cooled 865s could benefit from a six speed.
Owners also wanted more power.
With the 1200 water cooled, they got that in spades, especially torque. Now the sixth gear isn't needed, IMHO.

Glen

If I had a road bike, I would want six gears. But the reason I don't ride a road bike is that in Australia - if you lose your bike licence, you also lose your car licence.

acotrel said:

If I had a road bike, I would want six gears. But the reason I don't ride a road bike is that in Australia - if you lose your bike licence, you also lose your car licence.

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No different to Europe then!

i have a 5 speed in my race bike, I need to change rear wheel gearing to suit different race circuits, others run 6 speeds and dont need to change gearing as they just stick to 4th and 5th for the shorter trackers 5th and 6th for the longer tracks.
I have a standard 4 speed AMC in my road bike although gearing is a little taller than standard as I have a Maney belt drive in the primary and 21/42 for the final drive ratio.
I dont ride at 100mph so find the long stroke torque is great with the 4 speed.
As Fast Eddie says , horses for courses !

Is there a difference in the widths of the gears for 5 and 6-speeds? Seems like I remember reading the Quaife 5-speeds had narrower-than-stock gearsets. Nortons have a pretty flat torque curve, so is 6 necessary for anything other than not wanting to change the rear sprocket at the racetrack? If you already have 5, does it sacrifice any reliability with 6?

Quaife



TTI

Stock


Helpful link
https://www.nortonownersclub.org/support/technical-support-commando/gearbox-ratios

Danno said:

Is there a difference in the widths of the gears for 5 and 6-speeds? Seems like I remember reading the Quaife 5-speeds had narrower-than-stock gearsets. Nortons have a pretty flat torque curve, so is 6 necessary for anything other than not wanting to change the rear sprocket at the racetrack? If you already have 5, does it sacrifice any reliability with 6?

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When I first raced my Seeley 850, I tried it with the standard gearbox. It was absolutely hopeless - the bike was too slow everywhere. One of my friends said 'if you have a torquey motor, you don't need a close ratio gearbox. I don't think he had ever ridden a bike which had a close box. When you race change up through a close box and keep the revs high, the Commando engine performs much better. If you let the revs drop, it takes an eternity to get them back. with the heavy crank, the motor tends to spin up at the same rate regardless of the gearing. If you lose 1000 revs on a gear change getting them back is nothing, but if you lose 2,500 RPM, you will wait forever. When I change gear coming up through the box, I ease the throttle to take the loads off and stand on the gear change. The acceleration when you do that, is superb. Coming down through the box, a slight blip of the throttle is enough to match the revs. With the wide box, it takes a heap of revs to get down one gear, so being smooth is impossible. I now have a 6 speed box, mainly to get the two lower gears for the clutch starts in races. The first two corners in any race are extremely important. With four speeds close ratio, they are usually either all too high, or all too low. So you chose where you want to lose a race.

If you have not ridden the same bike with both wide and close ratio gears, you might not really be aware of the difference in performance. For a road bike, it is probably irrelevant.

The RD400 Yamaha two stroke has the same gearbox ratios as the TZ350 racer. Some of the guys who race RD350s use those gears, or a similar set from the Banshee. The RZ350 Yamaha was probably the most developed of Yamaha's street two strokes and probably has those gears. It does make a difference.

Danno said:

Is there a difference in the widths of the gears for 5 and 6-speeds? Seems like I remember reading the Quaife 5-speeds had narrower-than-stock gearsets. Nortons have a pretty flat torque curve, so is 6 necessary for anything other than not wanting to change the rear sprocket at the racetrack? If you already have 5, does it sacrifice any reliability with 6?

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The gear width difference is the case for the Quaife boxes based on AMC cases. It is one of the reasons I chose to run a 4 speed in the '70s, and yes those Quaife 5 speed boxes were less reliable, particularly those that had a kickstart mechanism and ran the layshaft in the bush like a standard box. Though to be fair, the main issue was shaft flex not gear width.

But if Yves chooses a 6 speed it will be a TTi. This is a completely different proposition. Because, not only do TTi use larger diameter shafts and bigger bearings, but TTi cast and machine the cases and are free to play with the case width and shaft length to accomodate wider gears.

The 6 Speed TTi sacrifices very little in reliability and can handle the power even a highly tuned 750 Commando engine can present to it, and I should think most 850s. But TTi do an 'XHD' 5 Speed, it is stronger and a better choice for 920 plus motors, when in any case it is a more difficult argument to make that you need 6 gears with all of the mid range available.

Mick Hemmings will tell you his current 5 or 6 Quaife builds are far more reliable than the '70s versions, I have no reason to doubt that, and the 6 speed is now widely used in 500cc race bikes.