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Throttle response
I have a more general question regarding the xt660 that also includes other bikes.
I have had several bikes and one thing that I like in a bike is throttle response and I think that is what is missing from the xt to be a fun bike. For example the KTM 640 that I owned a couple of years ago had a CV carburettor. The throttle response on that bike was the same as for the xt660. I test rode a friends KTM 625 that was equipped with the exact same engine but had a Keihin flatslide carb. The difference was huge so I got myself a Keihin that transformed the bike totally. The same I have also done with two of my old Ducatis, 900 supersport (CV) and Ducati 750 supersport (CV). I replaced the CV carbs with flatslides. Huge diffrence! I would like to have the same throttle response on my XT660 but keep it injected. What can be done? I know that the new KTM EXC bikes have injection and they have the throttle response that I am after. So it can be done with injection but the question is how? Has anyone tried for example another injection system on the xt660? e.g megasquirt or even put a Flatslide on ? |
Would you describe the difference in riding / throttle response?
Have you considered a Power Commander with custom fueling map? Anyway, you got my attention at "megasquirt". |
what xt have you got? x, r or z?
I think what your really talking more is not response but free revving under load, as the xt motors spin up freely when not loaded but on a standard engine, in gear under load it takes a while to rev the engine trough the range. I think you will be looking at the basics of air filter replacement, fuel mods (either kevs or PC's) and exhausts. each will help the engine take in more air, make more of a bang and allow the fuel to exit the engine better |
"but on a standard engine, in gear under load it takes a while to rev the engine trough the range"
im not to far away from standard but i go from changing gear to limiter pretty quick tbh it do sent take awhile on mine untill about 70 mph its change gear hit limiter change gear hit limiter its not like it take time to climb |
Maxwell12345: Yes you are on the spot, it is the free revving under load that is damn slow on the XT660.
If any of you have ridden a KTM with flatslide, be a 625 / 660 or a XC or EXC you know what I am after. I know the XC and EXC are competiton bikes that cannot be compared but I know what a huge diffrence the change of carb did to my KTM 640 and the ducatis. I think that the free revving of the XT660 is like a CV carb model, sluggish and with lack of "temperament". My bike is a Xt660X -2004 with DNA stage 2, snorkel removed, KEV mod but standard exhaust (I like it silent..). I have considerd a Powercommander but I do not think that it will accomplish what I am after. Or it could be that simple it is just lacking power? I am used to stronger bikes. But I also feel the same diffrence on cars, some are with more temperament and throttle reponse. Compare a standard Alfa romeo to a Volvo, both can have the same horsepower and tourqe but it is delivered diffrent. I would say that the XT is a volvo and the KTM is the Alfa Romeo. |
Would you describe what you are after as:
* more elastic engine (more useable from down below 3000rpm than stock) * faster throttle response (faster delivery of power to the wheel) * better take performance * different "feeling / feedback" to the rider * different torque pattern (eg. more low-end torque vs more high-end extension) * more HP to the wheel ? |
Its the crap fuel injection:rip[2]:.A big carb far better.:newspaper:
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The KTM's are a lighter built motor with a lot less
internal mass to accelerate... The XT can be made to rev out more freely..but It's not a KTM and will never be one... |
The biggest gains from these motor are from the intake side, you try & run fast with a big sock rolled up in your mouth.:Itching_KFKKYE:
You can compare a KTM big bore short stroke quick revving motor to a long stoke motor, the shorter stroke will always rev quicker if both bikes are standard, but there is some thing you can do to a XT, if you had to ride Kriss007 XT it would smash any KTM 690 by a long way with 76 rear wheel HP. |
I would not say that the diffrence in stroke and bore between the Ktm 690 and 660 is that different:
Ktm 690 bore/stroke 102 x 80 Yamaha 660 bore/stroke 100 x 84 The rotating mass could be the big culprit. The xt has a huge wflywheel and probably a big counterbalance weight, and also a steel basket clutch. There could be a lot to win if one would reduce some of that weight but most often that only affect the free revving with no load. |
I only did a couple of mods on my 2012 XTX, but already with full exhaust (homemade - i work with stainless steel pipes on a daily basis) and airbox mods (DNA stage 1 + 2) and Kev's fuel mod / or PCV it's a huge improvement.
I also do a lot of roadracing (race prepped SV1000N) and Enduro riding on a 2006 KTM 450 EXC so i know exactly what you mean. :) I am doing some mild head porting and and fitting a stage 2 Hot Cam during the Winter on the XTX, and i think that will get me where i want to be in terms of throttle respose... Going further that that, i believe will be a lot less cost-effective compared to just getting another bike. As of now, i threw just under 750$ at the bike for the different mods, and that includes the complete Raptor 700 head i had to buy on fleabay to get the cam idler gears for fitting the cam to the XT head. |
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