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Discussion Starter · #1 ·
OK, checking if anyone else has encountered this - between 3k and 5k rpm the bike surges up and down when maintaining constant throttle. Its not me moving the throttle, if I keep it perfectly steady it still surges up and down a little.

Open the throttle and its fine, just when trying to maintain low speed. Only really noticeable in gears 1 through 4. Not so noticeable in 5th and 6th.

Only mod to the bike is an IXIL exhaust. Bike has only done 700ks.
 

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Its the fueling ratio, basically the way the ECU map has been written. The guys on the 690 use an O2 mod that plugs into the Lambda, it helps to smoothen the chugging. The Powertronic almost eliminated this on my bike, I can cruise at lower speeds but its still there. Best way to get around it is to go down a gear and have the revs higher.
 

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Discussion Starter · #3 ·
Thanks dan1. Wasn't the response I was looking for, but been riding it with a few more revs lately and it seems smoother.

It was more of an issue when its cold as I'm not wanting to rev it til it warms up a bit.
 

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This syndrome is more pronounced when the engine is cold. Once the temp. gauge hits about 4-5 bars, it gets lot smoother. Until then, there are lot of jerks and throttle seems like a wild horse.
One thing which I noticed is that after piling up more and more miles, the ride gets much smoother.
But yes, there is always some amount of roughness even when hot.
 

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surging power and jerky [email protected]

hi eatof, dan and sid - same problem here - jerky ride and power surge in the region of 3000 - 4500 rpm, more noticeable in lower gears and speeds, and occurring while maintaining a constant rpm. Am taking the bike to the dealer on the 15th and having a technician check it out. Will let you guys know if anything helpful comes off it. In the mean while, could you find a solution or explanation?
Thanks
 

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Discussion Starter · #7 ·
No solution yet unfortunately, bike is going in for its first service on Friday. I'll see if they can have a look at it for me.
 

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I had a similar behaviour when I got the bike from the dealer but it was so dramatic that I decided to return the bike to the shop for inspection. After one month of "try and test" they found out the root casuse was a defective ECU mapping. They just re-flashed it and then it was ok. The problem was they nearly dismantled the whole bike before discovering what was wrong so I had the feeling I was getting a second-hand bike :mad:
 

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it could very well be possible its pure oem tuning

a quick check of the stock tuning numbers could maybe show us what is wrong
 

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hi all. took my bike to the dealer Bajaj Auto Siliguri. the proprietor Rahul has been very helpful and got the ECU changed and he also had a technician come in from outstation to look at this. it feels a lot better now though I can still feel some jerking in the 3000 rpm region in the lower gears which I am pretty sure is not a throttle control issue. hope it evens out eventually. thanks to Rahul for taking the issue seriously and hope it resolves itself out finally. cheers...
 

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As an experiment I recently removed the rubber intake snorkel from the air box. I cannot recommend this because it significantly reduces the usual torque surge above 6000 rpm which is such an enjoyable feature of the bike. But I did notice that there was a good side effect in terms of the surging or shunting issue at low speed on a light throttle. I would say that it allowed the bike to trickle along in one gear higher than before when in traffic and/or speed limit situations.

This suggests that the problem may be that there is a critical air flow speed in the intake where the flow changes from lamina to turbulent and this flips from one to the other in these conditions. For those that understand cricket this is much as a swing or spin bowler gets sudden swerve or dip on the ball as its speed drops in flight. ( Sorry I don't know if there is a baseball equivalent!)

So a possible solution would be to create turbulence in nearly closed throttle conditions but if this is done at the air box an external fuel controller is definitely needed to get back that lost mid-range torque.
 

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When I added the DNA air filter the stuttering reduced, has a greater flow than anything else on the market so you may be onto something. The fix is actually really simple but Kev is hesitant about making them, the same O2 loop controller used on the 690 can be done for the 390. He's concerned that a particular country will just copy his mod so hes not to keen to make the 390's. Its a shame too because every 690 owner automatically buys one to stop the bucking.
 

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Is this something PowerTronics could add, what is the fix exactly, adding a wideband O2 sensor?
 

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Apparently they have one but I never bothered looking into it, the stutters are virtually non-existent on mine nowdays.
 

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Hello! I got my bike on 2015-05-01, and really feel this surge in power just like is described here.

Considering this thread has been inactive for a while, does this mean the issues smoothes out after a while?

Thanks!
 

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Hello! I got my bike on 2015-05-01, and really feel this surge in power just like is described here.

Considering this thread has been inactive for a while, does this mean the issues smoothes out after a while?

Thanks!
You get used to it, or you manage it with clutch and/or revs, it doesn't go away. A fix is on the way though, just hang in there.
 
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Just to put things into perspective though - this is not a really big issue at all.

Each bike has it's own few faults you have to live with or manage by adjusting your gears / shift points etc.

This is a single cylinder high compression engine with the base ecu mapping not bad at all considering the different countries and climates / fuel types the bike has to work in.

I have not changed to a power commander or anything else - stock exhaust etc and do not notice this surge at all anymore- might be using a little bit more clutch or gearing up / down quicker.
 

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I'm wonder if anybody has flashed a bike with the Akrapovic software w/o actually having the pipe installed...might fatten the mid-range fueling just enough to lose the stuttering. IF I was a dealership tech I'd give it a go...in fact, I may get mine to try it just for the h**l of it. Heck, it's just software, right .....

Pete
 

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Having owned multiple Superdukes that are renowned for this, along with 5 Yamaha XT660X's which are also prone to it, you guys (and me) have it easy with the 390, honestly, the surging compared to many other bikes is absolutely minimal.


On all of the others it's down to SAS/O2, etc and emissions. There's always a fix in the end, but it's always aftermarket, not the bike supplier who comes up with it.


Now that these bikes are being raced in the UK in BSB series we may start to see more mods/fixes potentially I guess.


the problem comes that you always need several new people with great technical knowledge to start with the modding before you get any real answers.
 

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I mean KTM should have named the motorcycle KTM JERK 390, the bloody thing, vibrates, jerks and helluva lot fun!

After all jerking is fun indeed, don't you guys think! lol



I'm wonder if anybody has flashed a bike with the Akrapovic software w/o actually having the pipe installed...might fatten the mid-range fueling just enough to lose the stuttering. IF I was a dealership tech I'd give it a go...in fact, I may get mine to try it just for the h**l of it. Heck, it's just software, right .....

Pete
That's the evilest, yet brilliant thing I can imagine!

Cheers!
V
 
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