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I rode the 390 with the engine light on and the RBE set to +1 as you indicated. After 20km I stopped, waited 2 min. and then did another 20km.... Same procedure - light still on. At the third stop I said to myself "Ya Whyzee...." But then the light went out... I was so glad I nearly forgave you.... but the light came back on. I said to myself "Ya Whyzee"... and then the light went out again! So I stopped at KTM and they did a reset on the bike. I saw the tail pipe was very dark and noticed that where I normally averaged 3.5 l/100km the bike now used 4.7 l/100km - indications of too a rich mixture! Before I left KTM I changed the fuel setting from +1 to ZERO.... The bike is less smooth and on the return trip (120km) used 3.9 l/100km.... but the light stayed off. (KTM said they often see the light come on after a BP or RB installation and tell the client to live with the light....)
What an absolute crock ! - Live with the engine light coming on FFS !

I think the bloke who first started saying the 390's "run lean" was the same bloke who told us that the earth was round - and everyone started believing him !

All bike manufacturers are in the same boat with emission standards these days - my previous bike - a 2018 Honda CB300R - single producing 30hp out the box was a smooth as silk - same emissions regs as the ktm have for the 390 - But the 390 has a tuned up 370cc single - so, its never going to be like a lower hp single, (or a 2/3/4 cyl for that matter)......but...

As i have said many times - the best (and cheapest way) to get rid of the jerkyness, is to either go plus 1 on the front sprocket or minus 3 or 4 on the rear sprocket)...... no engine lights coming on, no increased fuel consumption and no forking out hundreds for a "box" - after the sprocket fitting, the bike is transformed and much much nicer to live with day to day.....

in the real world, all these fuel boxes are doing is ramming more fuel into the bike, which it doesn't really need - costing you money to buy the box and costing you money cos of the fuel the bike now drinks ......

Don't you honestly think if the bike was really crying out for the fuel imput to be increased, then KTM would have offered a re-map service at the dealers, as they did on the Gen 1 bikes ? - KTM btw do smaller (and larger if that float's the boat) rear sprockets off the shelf - i wonder why ??

And tbh this extra fuel is going to do fugger all to increase performance - same as fitting an "annoy the neighbours" after market exhaust.....

its your money, but inmh opinion don't waste your money frecking about with these boxes - cheage the sprocket and leave the zorst well alone and enjoy your bike !
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Glad it improved your bike.

l am always surprised that none of the road tests/reviews of this bike mention the low speed running issues.
Most road tests of this bike are not in the UK.

I wonder if the ECU map is different for other markets and here in the UK we get the lean fuelling map to pass emissions.
Also, I’ve not heard anybody on this forum from lndia or the US complain about the low speed running of the bike.
Road tests by Missenden Flyer were UK based and never found any issues with low speed running. But then I never found any low speed running issues with this bike. It runs at low speed just like every larger four stroke single I’ve ever owned. I suspect it’s a matter of expectations.
 

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Discussion Starter #63 (Edited)
The 2018/2019 390 runs lean! Fact! And so does my 2019 Super Duke R. New emission rules from Hitler's daughter in Brussels.... "make 'em leaner"... and therefore bigger radiators are fitted (2020 SDR) to deal with the extra heat. The 390 surely runs much better with the RBE and does not have that "twitchy" throttle in traffic. Fact!

Read: The following has all the scientific info... leaner / cleaner / hotter / more snatchy ...

 

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That article literally says that snatchiness is as much the manufacturers fault as it's Euro's. Also, says nothing about lean burn.
With every new Euro version, the requirements become stricter than before, but it's not true that the fix-all solution is to keep leaning the mixture.

That's not to say the Duke is correctly tuned, it may very well be to lean. However, not all Euro 5 bikes are hard to ride at low speeds, this might be just KTM not being able to figure out how to tame that thumper, or maybe deciding it's not worth the R&D cost, or maybe even testing on focus groups that liked that "character", who knows. Or maybe it's Euro.

FWIW, changing the sprocket has a considerable downside - worse acceleration. This isn't a powerful bike as it is, adding long gearing makes it even less so.
 

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I didn't feel like reading all of this.... but I will throw out that I did some testing with the RBE to include some datalogging, its in one of my post.
 

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You have a point, I forgot you guys are talking about 2nd gen 390's. I've heard from others that they did increase fueling on 2nd gens.
 

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That article literally says that snatchiness is as much the manufacturers fault as it's Euro's. Also, says nothing about lean burn.
With every new Euro version, the requirements become stricter than before, but it's not true that the fix-all solution is to keep leaning the mixture.

That's not to say the Duke is correctly tuned, it may very well be to lean. However, not all Euro 5 bikes are hard to ride at low speeds, this might be just KTM not being able to figure out how to tame that thumper, or maybe deciding it's not worth the R&D cost, or maybe even testing on focus groups that liked that "character", who knows. Or maybe it's Euro.

FWIW, changing the sprocket has a considerable downside - worse acceleration. This isn't a powerful bike as it is, adding long gearing makes it even less so.
Don't knock it untill you've tried it ! - In my humble opinion, having tried it, the Gen 2 390 is mental away from the traffic lights and you need to change to 2nd almost immediatly, then 3rd not much after - the sprocket change calms the bike down, removes the jerkyness and makes the bike much nicer to live with day to day - Without changing the bike's characteristics....oh and cruising down motorways / dual carriageways is a lot more relaxed....

From the "piggy back / booster plug etc" thread - The Bike man from BKK him say "change the rear sprocket - don't waste your money on anything else"..... i would suspect he knows more about and has had more "hands on" experience on the Duke 390 than anyone else on this forum.... People who are trying to flog you these boxes / pipes have a vested interest - he has none.....

God, I'm starting to sound like Henry Fonda in "12 Angry Men" ......
 

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my bike is 2016 model and it was literally impossible to maintain 8 mph smoothly in 1st gear without using the clutch, with the boosterplug fitted it is now possible,
it was also impossible to maintain 12 or 15 mph in second gear smoothly without using the clutch, again it is now possible,
changing final gearing ratios would not change how my bike reacted at tiny throttle openings, when you change gearing you can only change so far until 1st gear effectively becomes the same as the standard 2nd gear, basically like losing the standard 1st gear,
if changing the gearing on your bike helped then that is great, but don't assume one method will help in all cases, check out youtube videos to see how many brands of bike get improved low rpm running according to their owners by fitting such devices,
maybe this engine is as it is at low rpm running is because it was destined to be in an off road bike where it would be used hard,
you also have to remember that we are from different countries and our atmospheres and air qualities may be better or worse than others for our bikes which will make them behave differently, also the quality of fuel may differ from country to country
 

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my bike is 2016 model and it was literally impossible to maintain 8 mph smoothly in 1st gear without using the clutch, with the boosterplug fitted it is now possible,
it was also impossible to maintain 12 or 15 mph in second gear smoothly without using the clutch, again it is now possible,
changing final gearing ratios would not change how my bike reacted at tiny throttle openings, when you change gearing you can only change so far until 1st gear effectively becomes the same as the standard 2nd gear, basically like losing the standard 1st gear,
if changing the gearing on your bike helped then that is great, but don't assume one method will help in all cases, check out youtube videos to see how many brands of bike get improved low rpm running according to their owners by fitting such devices,
maybe this engine is as it is at low rpm running is because it was destined to be in an off road bike where it would be used hard,
you also have to remember that we are from different countries and our atmospheres and air qualities may be better or worse than others for our bikes which will make them behave differently, also the quality of fuel may differ from country to country
16's are different bud, I have a 16 and the fueling issues are def real with them.
 

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Do you REALLY think the Earth is not round?
 

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Gen 1 bikes were definitely rougher at low revs but whilst KTM smoothed out the low end of the gen 2 map I’m not convinced that they made it less lean. The gen 1 bikes are reported to faster. I suspect all KTM did was to smooth off the power peaks at low revs, reducing the fuel input and making it smoother but slower. On a gen 2 bike nothing exciting happens at low revs.
 

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Gen 1 bikes were definitely rougher at low revs but whilst KTM smoothed out the low end of the gen 2 map I’m not convinced that they made it less lean. The gen 1 bikes are reported to faster. I suspect all KTM did was to smooth off the power peaks at low revs, reducing the fuel input and making it smoother but slower. On a gen 2 bike nothing exciting happens at low revs.
Ive owned both Gen 1 and Gen 2 390's and riden them both un modified and fettled ...... the Gen 1 out the box was lumpy bumpy and jerky as fruck ..... then you go on that journey to get it be nice to live with on a day to day basis - for me it involved a -3 rear sprocket - it was good but the bike still needed more fiddling with..... then had internal parts of the zorst removed by the KTM Dealer (bit louder but not crazy) and then they re-mapped it - quoting a " plus 6hp" increase ..... you certainly could feel the difference and it was much much smoother and easier to live with - would it be faster than my Gen 2 - with -4 sprocket and k and n filter ? god only knows .... almost a year appart for one ..... all toll'd - the Gen 2 is a much much improved version of the 390 and imho, needs minimal faffing with compared to the Gen 1 .......if you were today looking to get a s/h 390 - i'd recommend giving the Gen 1 a wide birth and going for the Gen 2 ....
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When the 490 hits the shores later this year, you can bet your bottom dollar that it will be a huge improvement over the Gen 2 390 ......
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I have fitted the BoosterPlug, very straightforward. Yes all if does is fool the ECU it’s 20 degrees cooler than it actually is, but the result is 6% more fuel across the Rev range. It sits between air temp sensor and ECU. When on a constant throttle, the ECU takes its info from the lambda sensor and rights the mixture. My wife’s bike ran like a bag of **** with a decat fitted, added the plug and she is now running a dream. If you’re not doing any more mods than decat & airfilter, I’d recommend the BoosterPlug. ?
Hi can you tell me where you chose to site the sensor for the booster plug please?
 
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