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ttr speeds
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whats the typical speeds the ttr can go mine is standered and with trail wing tyres at 14psi tops out at 135kmh but feels more comfortable at 100-110 kmh. does this sound about right.

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That's sounds about right to me, obviously depending on gearing, mine was fairly high geared and would cruise at around 65mph then top out around 80mph

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yeah mines about the same managed to get 141kmh out of her but that gives your chest a good work out


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I have developed a spreadsheet (in Microsoft Excel) that will show the speeds in the gears for a list of variables.

In the spreadsheet you can choose the engine revs, the gearbox sprocket size and the rear wheel sprocket size.

The sheet then provides the mph using the various selections in all the six gears using the standard box ratios.

Since the TTR sprockets vary from 13, 14 and 15 for gearbox and 44, 46, 47, 48, 50 and 52 for rear wheel the variations are many.

I'll give the max and min of these choices - at 7,000 rpm (Maximum torque):-

15:44 = 81mph
15:52 = 69mph

14:44 = 76mph
14:52 = 64mph

13:44 = 70mph
13:52 = 60mph

So, given that Mr Yamaha fitted standard 13:48 teeth then at 7,000rpm top speed would be 64mph
For my TTR I've chosen 14:52 and this equates to a similar top speed of 64mph

So really, you choose your sprockets and take what you get.

Martyn



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I believe I saw 140kph on mine when it had 14/44 gearing.

On a test ride of a 2nd hand one at the bike dealer (with 14/44), on a short burst it would achieve 100kph
in 4th, 5th OR 6th gear, but not much more.

can you trust the speedo? who knows?
can you trust your gps indicated speed? not over a short distance.
can you trust police radar? maybe.

now with 13/46 gearing I haven't tried, and don't really care, but I can say that it sits nicely on 120kph without effort.
same speed as a friend on a WR250R who claimed at the time the WR250R wouldn't go faster in 6th gear,
but he had standard gearing, and I reckon he could easily exceed 120kph if he changed down to 5th.

hint: if you want to claim the world land speed record for street legal TTR250 with gearing change
being the only allowed modification, you would probably pick a gearing which gives 145kph (being
ambitious here?) at the max power rpm of 8500 - max speed is always near max power with
correct gearing (torque is nice for getting there, but power sets the limit).
You would have to be nicely aerodynamically tucked in of course.

of course with low gearing, you would get max speed a an rpm a bit higher than 8500rpm!

has anyone found the rev limit of a TTR250 yet?



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brindabella wrote:

has anyone found the rev limit of a TTR250 yet? 


No but I would be interested! Is the rev limiter built into the CDi?

In terms of gearing, most TTRs won't rev out in 6th on the standard 14/44 gearing (except on a long downhill) and will, typically, go faster on lower gearing which may seem counter intuitive.... 

Brian



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one would reckon a rev limiter should be in the CDI.

but being designed such a long time ago, maybe it doesn't have a limiter??
back in the dark ages, your only rev limiter was valve bounce.

but given that even a honda ct110 "postie bike" (design pretty much unchanged
for 20 years, and looking like a relic of the 60's) has a rev limiter, you would hope that
yamaha would have built one into the TTR250, if only to keep warranty claims down.

I know it should be easy to check - just go out onto the street,
and open the throttle fully in 2nd or 3rd gear and it should become obvious after a short while!
but if it hasn't got a limiter, that test outcome would not be good for the engine.

anyway, with a DOHC engine in a mild state of tune, not "peaky", you might hope for
quite a few more safe rpm after the 8500rpm power max.

I would love to know what the "red line" point is, but I'm not too keen on doing the test.

any volunteers? (tell us which gear what speed and what sprockets)

actually someone may have a 3rd party tachometer (eg "tiny tach") which could
give a safer, and more accurate, indication.






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TTRfan wrote:
brindabella wrote:

has anyone found the rev limit of a TTR250 yet? 


No but I would be interested! Is the rev limiter built into the CDi?

In terms of gearing, most TTRs won't rev out in 6th on the standard 14/44 gearing (except on a long downhill) and will, typically, go faster on lower gearing which may seem counter intuitive.... 

Brian


 It has a limiter in the CDI unit. You can buy aftermarket unit which is a de-restrictor. Search ebay & they are about AU $250.00.

It will obviously go much faster without it.

.................................................

Jarrah.

 



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I talked about this in my thread ages ago eg...Fitting additional lights and accessories & upgrading electrical components



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it won't bounce off the rev limiter like cars do just still at speed untill changed, found that will fifth overtaking cars just stopped at 116kmh no more speed then changed.

in a way it's a good idea really having the throttle limited if your going as fast as possible top speed it's not revving out or bouncing off the red line.

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hmm, overtaking in 5th gear with standard 14/44 sprockets..

according to Cubber's chart, at 7000rpm (max torque) the road speed is 122kph if in 6th gear.
so applying maths (from gear ratios in owners manual) max torque in 5th gear would be about 105kph.

the "seat of pants" feel would be a drop off in performance above that when overtaking in 5th, because there is less driving force at any higher revs, plus the ever increasing wind resistance, and the fact that this is NOT the most powerful bike in the world, is consistent with a feeling of a 116kph "sign off".

but if you work out the speed at 8500rpm (apparently the max power point) in 5th it is about 127kph, so at 116kph, you are not even up to the max power point, so no rev limiter ought to be cutting in.

from Cubber's figures, if the rev limiter cut in at 9000rpm, 6th gear would see 157kph on the speedo - clearly you would need to be going downhill though.

so a real conservative (low) estimate of approx max revs in gears (with 14/44 sprockets) would be:

6th gear: 150 kph
5th gear: 127kph
4th gear: 105kph

so if you want to hit the rev limiter on a flat road, you probably want to be in 4th gear!




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get to those speeds and the poor thing seems to be revving it nutts off it revs high for a single thumper.
I like to cruise at 60 but seems I don't use 5 to its advantage only time I did was chasing an sv650 down cat and fiddle

I've also got low tyre pressure 14psi trail wings at front and back so that would effect it am happy with, great little bikes.

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my 97 ttr 14/52 sprockets max speed 133 kmh

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Cubber wrote:

I have developed a spreadsheet (in Microsoft Excel) that will show the speeds in the gears for a list of variables.

In the spreadsheet you can choose the engine revs, the gearbox sprocket size and the rear wheel sprocket size.

The sheet then provides the mph using the various selections in all the six gears using the standard box ratios.

Since the TTR sprockets vary from 13, 14 and 15 for gearbox and 44, 46, 47, 48, 50 and 52 for rear wheel the variations are many.

I'll give the max and min of these choices - at 7,000 rpm (Maximum torque):-

15:44 = 81mph
15:52 = 69mph

14:44 = 76mph
14:52 = 64mph

13:44 = 70mph
13:52 = 60mph

So, given that Mr Yamaha fitted standard 13:48 teeth then at 7,000rpm top speed would be 64mph
For my TTR I've chosen 14:52 and this equates to a similar top speed of 64mph

So really, you choose your sprockets and take what you get.

Martyn


 What speeds would I be looking at for 14/47 and 15/47 . I need to replace my front sprocket but not sure witch one to go with , it has a 14 on it now but doesn't have the umf to get the front tire up at all just wondering if this would make a difference ?



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I got mine up to a gps verified 117.5kph on the weekend! I've got 14/47, I'm a fat mammal and it was downhill ;)

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Sweet , thanks for the reply mate 



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My chart says 71mph for 14/47 ratio

Image2.jpg

Martyn



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So would going to a 15 bring that up by much or would it be to much and become counter productive ?

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Sorry - you asked for that ratio in your original query and I hadn't noticed. 

15:47 ratio gives a theoretical top speed of 64 mph = 103 kph

     Image2.jpg

Martyn



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As a special favour to you all here is a LINKY that you can click to enter your own details in my spreadsheet and get your own results - in MPH and KPH

Put your bike details to the RED figures and press enter.

You will have to wait a second or two for it to work out the answers.

Martyn



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Thanks so much mate , I would have thought going up one tooth in the front would have used the top speed . Thanks for the link to I'll have a play around with it and see what will work for me .

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On an associated note...

My speedo (mph) has 55 marked in red and then a red band for speeds above this, rather like the red band on a tacho.

Does this mean it's not wise to go above 55? (Which TBH I rarely do)

Or is it a change-up indicator if you are still in 4th or 5th at those speeds...?

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I think it is just a recognition of what used to be the speed limit in the US of A....



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