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2014 KTM 350xc back fires on deceleration

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So I've installed a full FMF exaust (power bomb header and 4.1 exhaust), which makes a HUGE difference in power. The issue is, the bike now has horrible back firing on deceleration. It runs smooth and clean with no pops or cracks, while the throttle is on, but as soon as it is chopped (especially while being ridden), it makes all sorts of back fires. Engine is stock/mapping is stock/intake is stock. Has anyone ran into this after installing exhaust? Any fixes that you know of? Thanks guys!

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Everyone experiences this with aftermarket exhaust and stock jetting/mapping. A remap should be next in your upgrades :thumbsup:

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Thanks guys. I was hoping a re-map was avoidable, but it doesn't sound so. Finding a KTM dealer around me that has the user setting tool (let alone knows how to use it) is like finding a needle in a haystack. Without driving 2-3 hours away (and rolling the dice that the shop DOES know how to re-map the ecu), I'm basically out of luck until I find the tool locally. Thanks again for the help.

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Adjust TPS sensor richer.

plus one on the TPS, mine and another I checked were lean out of the box. Adjusted to 6.10 volts and runs better now.

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Thanks guys. I'm going to try one of Steve841's maps and see if it corrects. I've had the TPS sensor get off before (not sure how that happens), so I'll look into that as well. If I get the maps today I can test and report back.

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Try and ride it then install the maps ... so you get a back to back feel for the changes.

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So... I've had a chance to play with several of the maps, and ride each of them... including the available maps from KTM. Steve841 has a pretty good mixture, and I'm currently sticking with one of his. The bad thing is... I still have deceleration pop/pop/pop (yet, it's a little better, but not much). I think it's time to reorganize and start with the basics; aka, re-seal all the pipe connections with silicone and double check the exhaust port out of the cylinder.

 

I raised the TPS voltage to 6V as well, but didn't notice a change. It's currently still hovering around 6V, as several have recommended this.

 

Im definitely going to keep playing with the map structure and tweak a few things, but it's a great start. It's amazing that you can change the bike so much with a computer these days. I put in one of the KTM super soft maps for a lap, and it made the 350xc feel like an electric scooter (exaggeration). Very linear power curve. 

 

If anyone has more maps to try, I'll give them a test for ya (given they make sense and nothing looks ridiculous on the program).

 

Cheers.

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Try TPS setting at .70 or even .75  Running my TPS sensor at .75 with the EU map and FMF 4.1 slip on.  Bike runs great.

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Does 0.70 richen it throughout the range ?

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Make the fuel correction +5 on the 2 degree for 2000, 3000, 4000, 6000 rpms ... ONLY

 

If that helps but doesnt fix, try +8 ....

Edited by steve841
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Thanks Steve. I'll try in the morning. I dis-mantled the full FMF exhaust and resealed everything with hi-temp silicone, just to rule it out. I'm going to ride it as-is to see if there's any difference. Then, I'll start making the changes you suggested as necessary. I can ride and test right out of my house, so it makes things really easy to get quick results. I'm determined to figure this out. Thanks again for all your help.

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Well, I raised the 2degree range to +8 for 2000, 3000, 4000, and 6,000, but still no huge difference. The bike pops starting around the 4000 rpm range, and gets worse around 6k. TPS voltage is set at .7, and the pipe is sealed up tight as well. I tried to attach an audio clip, but TT doesn't allow it. I'm thinking my next step is to do a series of increases by +2 on the fuel mixture across the entire range. If the popping stops at the 4-6k mark, I'll work backwards from there. If nothing happens, I'll beg for everyones advice.

 

Any other recommendations Steve?... or anyone else?

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Hi Stevie?

Do you have any maps available to share?i got 12 350xcf with 365 big bore and akra pipe.bike runs great with my map I have from friend.i can send you mine if you wanna try

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Everything I have is on my site ... southfloridamxseries.com 

 

The 350 maps were a collaboration effort .... since I no longer have one.

Edited by steve841

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I'm going crazy. Sealed everything again, tried many different maps (ones that made sense and even ones that didn't), and still I get popping like a bag of M80's is going off. I'm sure there's something out there that someone has found to stop this. 

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So with the stock exhaust you had none of this? Did you remove or change anything else when you installed the exhaust? Have you tried to re-install the stock exhaust to see if it stops? Just wondering if it could be something else like air filter leak, something lose or not connected???. Good luck and post up the source of the problem once you track it down.

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