Six Speed upgrade for performance' sake (Legend). - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 40 (permalink) Old 04-28-2011, 08:48 PM Thread Starter
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Six Speed upgrade for performance' sake (Legend).

I have had the Legend for a short time now and am loving it. I have enjoyed the short ratio acceleration but am feeling a little short with the top end of the fifth ratio. The engine has so much more in it to be limited by gearing.

My questions (stock 2000 Legend): What would be the anticipated top speed with the sixth gear addition? where can I get the parts and for how much? Anybody in or near Tampa FL USA know how to do the conversion and willing to help me (do the work while I scratch my head, not a transmission guy)?

I've read several posts about the conversion but the popular reason to convert seems to be economy at highway speeds. I, of course, will benefit from the lower RPMs at speed as well.
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post #2 of 40 (permalink) Old 04-29-2011, 03:05 AM
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Originally Posted by captdramamine View Post
I have had the Legend for a short time now and am loving it. I have enjoyed the short ratio acceleration but am feeling a little short with the top end of the fifth ratio. The engine has so much more in it to be limited by gearing.

My questions (stock 2000 Legend): What would be the anticipated top speed with the sixth gear addition? where can I get the parts and for how much? Anybody in or near Tampa FL USA know how to do the conversion and willing to help me (do the work while I scratch my head, not a transmission guy)?

I've read several posts about the conversion but the popular reason to convert seems to be economy at highway speeds. I, of course, will benefit from the lower RPMs at speed as well.
Try first 18 teeth front sprocket, it is way cheaper and the result is same comparing to have sixth gear.
http://www.triumphrat.net/hinckley-c...8-6-speed.html
http://www.triumphrat.net/hinckley-c...ar-ratios.html
http://www.triumphrat.net/hinckley-c...sprockets.html
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post #3 of 40 (permalink) Old 04-29-2011, 04:23 AM
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I have had a 5 speed T'bird until a few weeks ago. The difference between 5th and 6th is only about 450 or 500 rpm at 80 mph. Hardly worth the expense in my opinion.

I use 5th gear, and 4th more often than 6th when I ride my TBS. These engines like to rev, and the redline is way up there at 8750 anyway. So 5 to 6 K is not really doing any harm. Only time I use 6th gear is on the interstate when I run 75 or above.

I think the advice to play with the final drive ratio by changing sprockets is the best thing to do.

Cheers,Denny
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post #4 of 40 (permalink) Old 04-29-2011, 06:29 AM Thread Starter
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My goal is to raise the top speed of the bike without lowing the final drive ratio (sprocket).
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post #5 of 40 (permalink) Old 04-29-2011, 06:37 AM
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My goal is to raise the top speed of the bike without lowing the final drive ratio (sprocket).
Why??? How fast do you want to go?

I am only old on the outside!
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post #6 of 40 (permalink) Old 04-29-2011, 07:09 AM
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+1 on the 18 front sprocket, gives plenty of speed and comfortable cruising.
Yes am wondering re how fast your thinking also, mine pulls easy two up in 5th from 4000 to 6000 on overtake but much more than that I get a punch in the ribs.
Took it to 180kph once but the corners were comming up too fast.
Just once :-)

Murray
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post #7 of 40 (permalink) Old 04-29-2011, 07:28 AM
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My goal is to raise the top speed of the bike without lowing the final drive ratio (sprocket).
Taking this & your original post together then, what you really mean is you'd like to optimise gearing for the highest top speed.

(Unless both of us have no clue whatever what it is you're after )

This means that the gearing must coincide the maximum power rpm of the engine with the maximum roadspeed which that power level can just, but no more, overcome.

Gearing choices like this are normally decided* by manufacturers by overlaying rear wheel power curves (at various ratios) on a graph of the vehicle's combined rolling & wind drag vs speed (a 'square law' curve).

But this get's tricky on a bike. The biggest factor is wind drag, but this changes significantly with different riders/riding gear/riding position & even different accessories such as mirrors! It should be obvious that fairings & windscreens can make huge differences - and in either direction, improving or worsening drag!

So that's your 1st thing to decide...you gonna be flat on the tank in riding leathers or flapping about in the (slower) breeze?

Then you need to guesstimate (not having any manufacturers or test data much) what speed you think the max power of the bike should be able to manage overcoming that drag.

Then another estimate/assumption needs to be made. That the rpm quoted for max power is actually the 'optimum' revs. (It would be close anyhow.)

Sooo.....put simply, with (stock) max power quoted at 8k rpm & knowing the speed you believe is possible in the conditions etc. you chose, that then gives you 'optimum' top speed gearing, however you choose to achieve that via combination of primary drive, g'box & secondary drive ratios.



*I actually did this as a placement student for what used to be Leyland Truck & Bus in a previous career incarnation!


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post #8 of 40 (permalink) Old 04-29-2011, 07:33 AM
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....and, er considering everything...that's an, er, 18t sprocket for me too !


98 Tbird tank/seat, Sprint fairing, ZX7R forks+Racetech Gold Valves, 08 ZX6R shock, short sw/arm, Alcon 6-pots, Ignitech+TPS, T'bike 3-1+Beowulf can, airbox/jet mods, tubeless wheel mod, lots :) per mile, 55mpg ave(imp)
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post #9 of 40 (permalink) Old 04-29-2011, 07:54 AM
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Originally Posted by Muzz Bird98 View Post
+1 on the 18 front sprocket, gives plenty of speed and comfortable cruising.
Yes am wondering re how fast your thinking also, mine pulls easy two up in 5th from 4000 to 6000 on overtake but much more than that I get a punch in the ribs.
Took it to 180kph once but the corners were comming up too fast.
Just once :-)

Murray
Since fitting the fairing I get 193kmh/120mph
And Ive still got the green cams to fit!

I am only old on the outside!
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post #10 of 40 (permalink) Old 04-29-2011, 11:37 AM Thread Starter
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here in Florida, we don't have a lot of twisties so straight line performance seems to be king. So much so there are crotch rockets with five feet long swing arms and nitrous. Granted I don't expect that kind of performance out of my Legend, but I was cruising with a few bikes and they left me after my bike topped out at 130mph. The bike easily climbed to that speed, seemingly cut short of it's abilities. I would be satisfied with 150mph top end. I have a feeling that is probably the range of the sixth cog.

I am also going to squeeze a little more power out of the engine with intake and exhaust upgrades (possibly a cam too). There is a lot of potential in this bike and it shouldn't take much to bring out that potential and make the bike the performer it knows it can be.

I find it entertaining when a "cruiser" with a windshield and saddle bags keeps up with a crotch rocket. Especially the look on the rider's face when they can't shake me! Sleepers Rule!

Yes, changing the front sprocket will increase top end speed but at the sacrifice of acceleration, especially at the top end. I used to have a '75 Chevy El Camino that would top out at 160mph. but it took five miles to get there. I changed the final drive from the stock 2.73-1 to 3.42-1. It made a major improvement to my acceleration but reduced my top end to 125mph.

Changing the front sprocket to a larger one would have the opposite effect on the acceleration in comparison to my old car. Ideally changing the car's transmission from the three speed to a four speed would have increased the top speed while maintaining the acceleration achieved through the wider ratio.

I believe adding the sixth gear will give me the performance I am looking for.
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