Im building a ktm 690 duke to run lightweight twins with and am trying to decide what chain and sprockets would be the lightest/ least amount of friction. Also gearing advice would be welcome.
Of the o-ring type chains, D.I.D. 520 ERV3. There is no lighter, stronger, slicker chain on the market. The key to keeping its low friction characteristics is to keep it clean. You can get chains with less "no load" friction, but they're not o-ring type and will require more maintenance than all the Kardashians combined. Sprockets...stick with known reputable brands that have survived - AFAM and Renthal - or give a look at upcomers like PitBull and SuperSprox. JT, SprocketSpecialists and Pro-Tec aren't what they used to be. Don't even bother with Vortex...you could hammer-forge beer cans into an harder material. Gearing...enough to pull redline in top gear, or just short of redline if you think you can draft anyone.
Not always necessarily true, would depend on the track. I know at NJMP for example pretty much everyone I know gears their 600's to only use up to 5th gear.
Gearing for redline is a start. Track dependent gearing is another topic that takes the bike into account. If a Duke is geared for 5th at NJMP, I don't think it will benefit. I know that the 5th gear set-up is popular on 600s at NJMP, but could there be an alternative benefit for gearing a 600 to 6th? Not that I have a 600 or know what the shifting routine is around that track for those bikes but, if they're only using five gears, why not use 2nd thru 6th? Seems to me it would act as a closer ratio transmission than 1st thru 5th. Again, that may not be what works there. What's the reasoning? (I've had this discussion before...I wasn't interested enough to remember the details.)
Ya i just got the duke last week. I havent taken it on any open roads to wind out high gear but in 5th it seems to top out about 100mph on the curvy backroads. Ive read 6th gear tops out at 125mph or so bone stock. This bike currently is bone stock but i am putting together my parts pile now to build it into a nice lightweight twin racer. Still trying to figure out what full fairing will fit it best and what gear ratio will b best for the bike once it is uncorked and has a streamline full fairing. I would think it should pull around 140mph on a long backstraight once its finished so il have to figure out gearing to accommodate that.
I'm not sure the full out Kramer race bikes built around the 690 motors hit 140 - so don't get your hopes up! I'd be happy with mid to low 130's on a standard Duke 690.
Thanks for the info and opinions. I will probly go DID chain and pitbull or renthal sprockets. Maybe 1 toothe up from stock on front sprocket and see if that will get topspeed from around 125 to 135mph, may need to drop a toothe or two on rear as well?
the best sprockets are the ones u get at 40+% off gearing always depends on the track and the rider's pace.
You'll have to pull a flat out run to see where the bike stops pulling. If it can't pull to redline what it has now, going taller won't help. All you end up doing is reducing the RPM that it stops being able to pull and you go slower. Unless you've increased the power significantly, going shorter always increases your speed and acceleration rate when compared to OEM street machines. (They are over-geared to reduce their noise output during EPA testing.) The engine will run higher into the RPM before it stops pulling. That higher RPM means it's delivering more power to punch farther into that aerodynamic drag which compounds exponentially. Add the advantage of a shorter gear making it easier for the engine to apply its power and now you have two things working towards punching through the air. You go faster...more quickly, too.
Thanks ya ive played with gearing on lots of other bikes but usually have kept around stock with my SV650s. This bike has exact same horsepower as an SV and the fastest i ever got a bolton sv was around 137mph showing on speedo. I would think this bike should show around same numbers. But this bike is geared a little lower than the SV stock. Im about to get track pack installed friday and i will put it in sport mode and take it up to the closest long straight near my house and see what it will pull in 6th and will post sometime next week what it runs.
Ya i know stock speedos can b 5-10mph or more off from a ligit radar gun speed. most of my jap bike seem to lie equally though like my gsxr 600 would show around 180mph toped out on flat ground and my buddies rc51 would show same numbers running right beside me. Even though we probly werent actually breaking 170 by what a legit radar gun would show. I dont know about the KTM though if its accurate or not? I would think probly should be about as much off as a jap bike.
Bike showed 122mh on digital speedo. That was rev limit 6th gear. It didnt fly up to that speed after about 118mh it was just kind of slowly counting up to 122. But with no bodywork and the supermoto bars the duke comes stock with preventing any kind of tuck and the factory parchute back fender i think thats not bad. Im gonna go up one on front sprocket and down a couple teeth on rear and see what it pulls after that. Will also remove the factory parchute back fender if it will unbolt without being cut.
RK GB 520 GXW is a highly recommended/proven chain. It has a higher tensile strength than the ERV3. And half the price. The only advantage the ERV3 has is it weighs 3 0z less. Just replaced the ERV3 that was on the RSV4 with the RK.....RK for the 600, 750 and it will go on the Tuono when I do the 520 conversion.