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From the day I bought my Duke until now, I have always believed that what riders perceive as "jerkiness" from the engine is due more to chain snatch than to rough engine performance at low speed. This discussion reinforces that belief. The low-speed snatch has never really bothered me and never been very severe: It disappears as soon as you get out of the low-end throttle range.

Oddly, since I have fitted my Loobman chain oiler, the chain snatch/roughness seems to have distinctly diminished, compared to when I was using spray-on chain lube. I think the chain is now happier, better lubricated, more flexible and less prone to tight spots, therefore less snatchy.

One gearing alternative that has received little discussion is the possibility of going up one tooth on the countershaft sprocket 15>16. I am far from an expert on chain drive, but I have read that a larger countershaft sprocket is easier on both chain and sprocket: It spreads the torque load out over a larger bearing surface, and the larger radius obliges the chain links to make a less radical, smaller angular turn at the countershaft. I looked at the gearing calculator site and saw that a 16-tooth countershaft sprocket with a 45-tooth rear produces almost the exact same gearing ratio as a 15-tooth countershaft with a 42-tooth rear. This might be a better way to modify gearing. Thoughts?

In the final analysis, both a gearing change and a piggyback are useful mods, IMO, though neither is mandatory. I plan to address the chain drive first, then think about a piggy.
 

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Will you are right by saying that the chain does contribute to the "jerkiness" of the Duke . I have felt the jerkiness caused by the chain increase when I fitted the X-ring KTM Powerparts ( orange ) chain . It deminised as the chain got " loser " with time .
 

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From the day I bought my Duke until now, I have always believed that what riders perceive as "jerkiness" from the engine is due more to chain snatch than to rough engine performance at low speed. This discussion reinforces that belief. The low-speed snatch has never really bothered me and never been very severe: It disappears as soon as you get out of the low-end throttle range.

Oddly, since I have fitted my Loobman chain oiler, the chain snatch/roughness seems to have distinctly diminished, compared to when I was using spray-on chain lube. I think the chain is now happier, better lubricated, more flexible and less prone to tight spots, therefore less snatchy.

One gearing alternative that has received little discussion is the possibility of going up one tooth on the countershaft sprocket 15>16. I am far from an expert on chain drive, but I have read that a larger countershaft sprocket is easier on both chain and sprocket: It spreads the torque load out over a larger bearing surface, and the larger radius obliges the chain links to make a less radical, smaller angular turn at the countershaft. I looked at the gearing calculator site and saw that a 16-tooth countershaft sprocket with a 45-tooth rear produces almost the exact same gearing ratio as a 15-tooth countershaft with a 42-tooth rear. This might be a better way to modify gearing. Thoughts?

In the final analysis, both a gearing change and a piggyback are useful mods, IMO, though neither is mandatory. I plan to address the chain drive first, then think about a piggy.
My Yoda of Dukes, I have to disagree this time. I installed the 42T sprocket first and the jerkiness was there to be honest worst since for the same speed the rpm was lower. After I installed the Rapid Bike Easy it disappeared. Now It is a little better and smoother than my old F800R that is twice the size of the engine. I already had several 650 single from Aprilia and BMW so I can say that now the Duke is better than those.
IMHO if you change the sprocket think serious about make the fuel delivery at low/mid better. RB Easy is the cheapest solution till now but the Dimsport don´t let me know how it afect the lambda´s signal and I do not like it since as an engineer I like to know how it´s affecting. I´m skretching my hand to make a reverse engeniring with an eletronic tools to see it.
Luis
 

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i think 43 hp from a 370cc single is a pretty high state of tune....
In the top end yes, but as seen in graphs above, most gains were made in the middle range, which has been everybody's experience here.
 

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IME What a piggyback unit invariably does on a across the frame four 1000cc bike, is fill in the emission dips and smooth out the delivery giving much better consistent fuelling across the board in pretty much every gear. Meaning that power is always on tap no matter what gear you're in, which is priceless. Getting 2bhp or even 10bhp at the top end means fuck all on a street bike. Where you need dependable power is for overtaking, a piggyback can do that and does do that if set up properly.

On a 390D a well set up piggy back does pretty much the same treatment, but because there's less power to start off with, having a healthy midrange is even more important, my Dynojet PC has done everything and more than I'd hoped for. It's a completely different animal compared to a standard bike.

I've got a 43T sprocket set aside (for when the OE chain is unfit for use) and when fitted this will exploit the healthy midrange (for a small single) it now has thanks to the PC.
 

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In the top end yes, but as seen in graphs above, most gains were made in the middle range, which has been everybody's experience here.
I agree. If you make more 2cv in an engine at high rev it will not make any difference in day by day use just if you is a racer track and you want to make the best and possible time. I already had bikes with 160cv under my legs and can say that out of track it is useless even considering that the police and law are not so strict here as in US, Europe and Australia / New Zealand.
But if you have an engine with a smooth torque curve you will thanks it everyday.
Luis
 

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How does the 43 tooth affect gas mileage? Cause after installing the Bazzaz I have lost about 10 to 15 miles per tank already. From about 130 to 120 per tank now.

Sent from my SM-G935P using Tapatalk
 

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Depending on which way you go with the gearing, you may labour or rev the engine more, in the gears, than previously.

Will most definitely affect fuel consumption
 

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Discussion Starter · #29 ·
Depending on which way you go with the gearing, you may labour or rev the engine more, in the gears, than previously.

Will most definitely affect fuel consumption
well thats good then - the 43 T sprocket makes the bike rev less...

think of all the money i'll save !
 

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How does the 43 tooth affect gas mileage? Cause after installing the Bazzaz I have lost about 10 to 15 miles per tank already. From about 130 to 120 per tank now.

Sent from my SM-G935P using Tapatalk
My 42t + RB Easy make my spend 7% more gas than original configuration. Sprocket goes one side and RB goes to the other.
Luis
 

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Enrichening the AFR - one of the principal functions of a fuel controller - means adding more fuel to the air/fuel charge for each piston cycle. Logic dictates that fuel economy would therefore suffer.
 

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If you add a potentiometer across the leads from lambda sensor, you can richen the open circuit to 13/13.5afr. i added a second one for good fuel economy with 14.5/15 and a switch on bar. I reconfigured PowerTronics so I could richen 6000 to 6200 to fix a flat spot.
I added a bung for a wide band afr meter in mid pipe. I don't know how to adjust ignition though. I might take it to a dyno shop to refine it. Anyway, its very smoothed out in first gear 3000 to 4000 and rips in all revs and throttle.
 

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You can adjust ignition with the PT free software. (R-Tune)

I love these older threads b.t.w. good and often inspiring answers/questions and solutions.

If you add a potentiometer across the leads from lambda sensor, you can richen the open circuit to 13/13.5afr. i added a second one for good fuel economy with 14.5/15 and a switch on bar. I reconfigured PowerTronics so I could richen 6000 to 6200 to fix a flat spot.
I added a bung for a wide band afr meter in mid pipe. I don't know how to adjust ignition though. I might take it to a dyno shop to refine it. Anyway, its very smoothed out in first gear 3000 to 4000 and rips in all revs and throttle.
 
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