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The TTR250 FAQ web pages -> TTR250 -> Carb stuff -> Slower throttle response compared to race bikes
Post Info TOPIC: Slower throttle response compared to race bikes
JCW


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Slower throttle response compared to race bikes
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As most of us have all known for years, barely twisting the throttle on a 250-450 race bike will make it launch hard.  The same throttle response on a TTR is much smoother and less aggressive.  For the first time the other day, I twisted it much farther and it flew from 40-70 mph with plenty of power left.  I'm guessing it could have easily reached 80+ mph based on how it was still pulling hard at 70 when I let off. 

I was in total shock that this little guy had an attitude if you twisted the throttle far enough.  Having ridden race bikes on single track for years I was not used to having to twist the throttle that far to make it light up and go.  I am confident that my bike is jetted correctly as it runs great from idle to top end, which is likely 80+ mph.   I will never know the top end speed, as I do not run anything WOT.

I checked to see if the throttle actually twisted farther on the TTR than my CRF450X, and the distance was exactly the same.  Based on that, I'm guessing it might be a needle issue.  Maybe race bike needles allow gas in much faster as you open the throttle??   With that in mind, has anyone changed needles for this reason, or does anyone have a another idea why this is happening.  I was about to sell my TTR, but that revelation made me decide to keep it.  I don't know if I want or need to change it since it runs great, but I am curious as to why the TTR needs a bigger twist of the throttle to light up and go hard.

Thanks,  



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TTRfan


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Hi John and thanks for an interesting post biggrin

The TTR250 will never get close to a race bike's acceleration when the throttle is cracked open quickly.

However, check that the accelerator pump is working on your TTR to make sure it has the best possible chance of competing!

You will need to drop the airbox back to see the nozzle at the bottom of the carb mouth. Crack open the throttle and check you get a good squirt of fuel in the direction of the slide. Not always easy to see.

The rubber on the diaphragm can perish over time and/or the check valve might be jammed or debris in the system between where the fuel enters and exits via the nozzle in the carb mouth.

Brian

 



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JCW


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Thanks for the reply. Mine runs really good, so I do not think anything is wrong with it. But, as I would expect, it does not have the race bike hole shot power of a true 250 race bike. But, from 40 mph to wide open, I don't think any 250F race bike will hang with it, or get anywhere close to its top end speed. My take away is that this is not a weak 250cc motor, as I originally thought. It is simply designed for commuting use more than low end torque/race performance. But, I may play around with a different taped needle or two if I get bored. Thanks again for the reply, and everyone know your little TTR is a polite fella, but he has an attitude if he gets fired up! Have an awesome day...and come on spring weather!

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Dan-in-a-Van


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It'd be interesting to try some timed 0-60's on a few TTR's. Mine definitely wants to get going as soon as I open the throttle. When the weather gets better I'll find a quiet road to give mine a try out against my RD350LC. 



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ttboof


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there are quick action throttle tubes available  the cam the cable wraps around is a larger profile .

the carb on the TTR has a tapered bore which gives the slower response from the same travel with the standard setup giving the repose we get on the ttr  , Ive often considered the quicker option but in the slow tight stuff it may be a disadvantage loosing the ability to make the fine adjustments .

your correct the ttr likes to get going in the top 3/4 of the throttle especially when geared down a bit



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Kaos


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Race bikes have really high compression short skirt pistons with aggressive cams, light weight flywheels, bigger carbs / throttle bodies and rev ungodly high to make impressive power. But that HP comes at a cost, increased wear and tear and intensive maintenance schedules, earlier rebuilds.

TTR's have heavy flywheels lower compression and are torqey low revvers in comparison. So they build revs slower and will never have the throttle response of a race bike. But the flip side is they last for tens of thousands of miles. :)

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Kaos


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ttboof wrote:

there are quick action throttle tubes available  the cam the cable wraps around is a larger profile .

the carb on the TTR has a tapered bore which gives the slower response from the same travel with the standard setup giving the repose we get on the ttr  , Ive often considered the quicker option but in the slow tight stuff it may be a disadvantage loosing the ability to make the fine adjustments .

your correct the ttr likes to get going in the top 3/4 of the throttle especially when geared down a bit

I'm chasing a quick action throttle for mine at the moment.   I found one laying around and tried to fit it up but the TTR's throttle cables don't fit the throttle housing.   With throttle control I don't believe the quicker response is a disadvantage in tight technical stuff, you can actually use it to your advantage.   My previously WR250F was as snappy as with a quick action Motion Pro throttle but like anything you get used to it.

Where I can get a quick action throttle one for the TTR250???

 



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ttboof


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Had a good search can’t find quick action duel cable units they all appear to be single cable nothing ttr specific 



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