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Discussion Starter #1
Hello there,
My name is Joel, I am new to Triumphrat.net. I have a 96 T'Bird which I bought in 2006. I am from WA but recently moved to the south coast area of NSW. I am wanting some info/advice regarding the RPM that my bike is doing at highway speeds. At 110kms the RPM is 5000, at 100 kms it's 4500 and at 90 kms it's 4000. The sprockets are standard so is it just the engine getting old? It feels like I need another gear! cheers
 

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Mine is a 2000 model with the six speed gearbox and it sits just under 4,000 rpm at a 100ks by memory. I know what one of the chain mobs list as standard on mine is different to my handbook. I'm working away at present and can't check that for you. A worn or old motor would still be doing the same rpm, check your clutch isn't slipping.
 

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You can usually feel something is not right when putting the engine under load and accelerating hard ie: sudden increase in revs that doesn't equate to similar increase in road speed. Also you say you have had the bike since 06, has it always done that many revs, have you changed your chain and sprockets recently and been given the wrong advice on what is standard gearing. Standard gearing can differ between countries on some bikes. I imagine a 96 is probably a 5 speed and it could be the reason they went to a 6 speed, not sure on final drive ratio, however these motors are capable enough to pull the taller gearing that would suit Australian conditions and may be worth experimenting. Noticed you have add for fork springs bought from yss in s.a. I have a post on here asking about yss rear shock on t-bird. If you haven't seen it and know someone who has tried one it would be good to hear about it. Cheers
 

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Discussion Starter #6
Thanks Pat.
The bike is a 5 speed and the problem does seem to have got worse over the last few years.
Stretching the brain cells and thinking back to the first few years I think the RPM at 100 k's was around 4000.
I did fit new sprockets and chain a few years ago which I bought from JCS in Perth. Considered changing the sprocket(s) to give lower RPM at top speed but decided against it and bought the standard kit. I think it was 46 teeth on the rear, don't recall what the front sprocket is.
From what you have said it sounds like I am up for a new clutch.
I don't know anyone who has tried out a YSS rear shock but I wouldn't recommend dealing with the guy at YSS in Adelaide, cheers
 

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Discussion Starter #7
Thanks Denny.
I haven't lubed the speedo cable but it doesn't seem to bounce around.
The tacho does swing around a bit sometimes then other times it nice and stable!?
 

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18T/43T.
In 5th gear, at 100km/h, I sit around 4400rpm.
I think 18T/43T is standard. If your front is 18T and rear 46T, your rpm would be higher at 100km/h.
 

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Some bikes came with 18T front and others with 17T.
AFAIK. all came original with 43T rear.


Since your tach is bouncing around some maybe it is just erroneous tachometer reading?

The symptoms of a slipping clutch would be the same for any motorcycle......So any decent motorcycle mechanic would be able to help diagnose that.

What about the oil? Do you have motorcycle oil in it? That can cause some slipping of the clutch.

If that is the case... You can run some conventional i.e. not synthetic motorcycle oil for a couple of thousand miles then return to synthetic motorcycle oil and it should be fine. Don't ask me how I know that works...
 

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Your clutch cannot be slipping in a manner that would give you a predictable change in cruise RPM. If it slips, it will hold at low power levels and in lower gears, and at higher power levels and in higher gears it will allow the engine to accelerate, as if you had intentionally slipped the clutch. The whole drive train is gears, chains and sprockets. Nothing in it can allow a gradual change in the RPM/KPH relationship.

If you changed to a 46 tooth rear sprocket, than that's when the change occurred, and it was immediate, not gradual. A weak engine will affect your ability to accelerate, but not the relationship between RPM and KPH. It's sort of digital; either it goes the right speed or it doesn't go at all.
 

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Discussion Starter #11
Thanks JVB

Instead of relying on my memory I should have done a count!
The rear sprocket does have 43 teeth and I am pretty sure the front has 18 as per standard, as you have stated.
So you are around the same; 4400 @ 100k's. Do you feel like you need another gear!? cheers
 

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Discussion Starter #12
Thanks WSC. I always thought that if the clutch is on the way out, disengaging drive/changing gears becomes a problem but once in gear the vehicle/mc will perform normally.
 

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Instead of relying on my memory I should have done a count!
The rear sprocket does have 43 teeth and I am pretty sure the front has 18 as per standard, as you have stated.
So you are around the same; 4400 @ 100k's. Do you feel like you need another gear!? cheers
Early on I did, but not anymore. You can always go to a 19T front, pretty sure some on this forum have done this, do a search.
I think from 2000 onward the 900 had a 6-speed gearbox but I don't know if the ratio was any different or if the 6th was like an overdrive.
 

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The 6th gear is higher than 5th, in fact, the 6 speed is the same gears 1-5 as the 5 speed. The effect depends on what front sprocket you have. (I had this all figured out once, but never wrote it down.) Anyhow, IIRC, the Thunderbird and TBS were the only bikes to get the 6 speed. A 5 speed with an 18 tooth front sprocket gets about the same gearing in 5th as a 6 speed with a 17 tooth sprocket in 6th. Personally, I think a 19 tooth front sprocket would be a little too tall on takeoff. I think the T-bird and Adventurer had 18 tooth sprockets with the 5 speed. Legend had 17 tooth sprocket, so same gearing as the TBS through 5th. Could be missremembering, though.
 

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Discussion Starter #15
Thanks again jvb & WSC.
Do you think a nearly bald rear tyre would make a lot of difference?
I wonder if I could contact Triumph GB for factory info of this kind?
 

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The factory didn't publish that information, but all the gear ratios and chain ratios are published. There are many spreadsheets available on the internet that will calculate speed vs. RPM for your tire size and primary, transmission and secondary ratios.
 

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Discussion Starter #20
So I had a look at the spreadsheets and it appears my bike is doing about 800 RPM more at 110 kms than it should be.
Something I just remembered is that for a few years now I have added "LIQUI_MOLY" friction additive into my engine. It is supposed to suitable for wet clutches but I am just wondering if that might be causing the problem.
Thanks again WSC and denny for the help.
 
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