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Popping on deceleration & how to fix it

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Popping on deceleration is obviously a common problem. I've seen many products or mods that are supposed to help but I'd like to hear what has actually worked. 

I have a '16 FE350S with all the smog stuff still on it. I've adjusted the TPS to .645 which seemed to help slightly. Then I removed the screen at the very end of the exhaust cap, which sounds better but pops more. I've got the BDSB fuel rail and 90* fitting to install yet. 

 

What's the solution that has worked for you?

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Have to de-smog. The popping comes from the smog stuff allowing fresh air into the exhaust system. Once I de-smogged popping was gone. 

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Popping is due to lean fueling. Get the EU or AU map. If you really want to do it right, get a PC 5 and have a custom map installed on a dyno. Desmogging is a start, but bike will still be lean and pop. Return all the shit to BDSB and get your money back! His stuff is snake oil. 

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4 hours ago, 1 lunger said:

Popping is due to lean fueling. Get the EU or AU map. If you really want to do it right, get a PC 5 and have a custom map installed on a dyno. Desmogging is a start, but bike will still be lean and pop. Return all the shit to BDSB and get your money back! His stuff is snake oil. 

What makes you say that about BDSB? The parts I ordered make sense to me. 

 

It looks like remapping is difficult to do now. No dealers will do it anymore. KTM/ Husky pulled access from dealers.

 

I will do the de-smog thing tonight. 

This is the method as it seems to me. 

Remove the seat, shrouds & tank

remove the muffler, header pipe and manifold

That should give access to all the smog stuff. 

Remove the charcoal canister.

Remove the SAS valve on the front of the cylinder above the exhaust manifold by removing the the two Philips screws, then unscrew it from the head and plug the hole with aluminum 12mm x 1.5 bolt

Remove hose and fitting from intake manifold and plug with bolt. 

Am I missing anything?

Edited by jeepdave

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49 minutes ago, jeepdave said:

What makes you say that about BDSB? The parts I ordered make sense to me. 

 

It looks like remapping is difficult to do now. No dealers will do it anymore. KTM/ Husky pulled access from dealers.

 

I will do the de-smog thing tonight. 

This is the method as it seems to me. 

Remove the seat, shrouds & tank

remove the muffler, header pipe and manifold

That should give access to all the smog stuff. 

Remove the charcoal canister.

Remove the SAS valve on the front of the cylinder above the exhaust manifold by removing the the two Philips screws, then unscrew it from the head and plug the hole with aluminum 12mm x 1.5 bolt

Remove hose and fitting from intake manifold and plug with bolt. 

Am I missing anything?

I have a FE 350 non S so I didn't have to do the desmog, but sounds like you got it right. I race my 350 and run the stock fuel rail without any problems. I think he comes up with things and then  makes videos that would scare anybody into buying his product. I tried some of his stuff (big bottom kit and end cap)  and it didn't make any difference. The custom cams, port and polish and valve grind did do the trick tho. 

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Those graphs don't show what the mods are between them. Not that I'm arguing. I'm not looking for more HP #'s I'm just looking for the engine to run like it should. Kinda sad after spending so much we have to make all these changes to make it run correctly but what can you do. 

Edited by jeepdave

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Seems like since I opened up the exhaust a little by removing the outer most screen(perforated metal) in the cap. The bike has been hunting for idle. Anyone have thoughts on how to get her purring?

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Hate to say it but you may need to turn up your TPS even more if you're not planning on a piggyback tuner.. But first, try turning up your idle to about 1800rpm if it's not idling that high once warm it should be. Also, adjusting your TPS up lowers the set idle speed so if you didn't correct the idle speed after tps adjustment that's probably a lot of your problem.

Finally, once you have it set around 1.7-1.9K RPM hopefully she sounds a bit more healthy. shut her down, then start her up without any choke, no throttle input, nothing.. And let her sit at idle for 5 whole minutes to reset the ecu to your updated A/F ratio, barometric pressure, and all that fancy pants sciencey stuff. Try it and let us know how what you think. I'm no mechanic, just sharing what I've learned from others. Peace

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7 hours ago, tyler90 said:

Hate to say it but you may need to turn up your TPS even more if you're not planning on a piggyback tuner.. But first, try turning up your idle to about 1800rpm if it's not idling that high once warm it should be. Also, adjusting your TPS up lowers the set idle speed so if you didn't correct the idle speed after tps adjustment that's probably a lot of your problem.

Finally, once you have it set around 1.7-1.9K RPM hopefully she sounds a bit more healthy. shut her down, then start her up without any choke, no throttle input, nothing.. And let her sit at idle for 5 whole minutes to reset the ecu to your updated A/F ratio, barometric pressure, and all that fancy pants sciencey stuff. Try it and let us know how what you think. I'm no mechanic, just sharing what I've learned from others. Peace

What should I turn the TPS up to? These things should really idle that high? That seems insane to me. Thanks for info by the way

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Have you checked with Thumper Racing lately to see if they are back in the "game"? :devil:

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I keep reading the idle should be set to 1800-1900rpm. How would I know what the rpm is? Is the a setting on the idle adjustment knob that gets close? I've been working on engines for a long time and info tune it by ear it's really low. How many clicks is roughly 18-1900 rpm?

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I plugged the holes in the intake and cylinder, let her run for 5 and she stopped popping while in the stand. She still hunted for idle once warmed up. I set the TPS to .601 and she popped on deceleration but not nearly as bad as before the delete. So I set the idle high and cranked the TPS to .738. She still pops on deceleration but not too bad at all. Found a place to remap the ecu but it's not local, I'd need to ship it out. Hmmm

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On my ride today I had the idle set pretty high by sound. Rode for around 40 miles to a dirt playground in the Mtns. I noticed the idle was not as high and it's die on me during slow technical obstacles. Not sure if it's me still learning the bike or fuel issues. So I dialed the idle up two more clicks. It helped but didn't solve it 100%. She wasn't hunting for idle at first but half way thru the ride I noticed she was hunting again. Not sure what to do about this. Any suggestions?

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Get the remap and put tps back to where it was , or ask the remapper where he wants the tps.

 

Jd jetting, noted in his testing, something weird on the 17's , they try to lean back out even if you move the tps. He  also Posted the Book spec for tps is .40v  with throttle valve fully closed and idle screw backed out.

 

Quote from JD

 

2017 KTM EXC and HUSKY FE TPS VOLTAGE AT IDLE, and the FACTORY REFERENCE- 0.400V:

The TPS setting at idle on the 2017's is unlike past year EXC and TE models. The previous throttle body DID NOT change TPS voltage as the idle speed screw was changed. The 2017 does move the TPS voltage when the idle speed screw is moved. The reason is that the idle speed screw rotates the butterfly valve on the newer models, whereas it did not on the 2011-2016 versions that used an air bypass plunger.

The TPS voltage per the service manual is referenced as "THAD" , throttle position sensor circuit A, at 0.400V, (+/-.004). The setting must be performed with the idle speed screw backed out to where the throttle valve (butterfly) is completely closed, as near as we can determine. The manual is very vague on this setting, and does not describe backing the screw out. After setting the TPS, the idle speed screw is turned back inwards and RAISES the TPS voltage to near .54-.55V , IF the idle speed is set per the manual on the 2017 450.

Using the KTM service tool, the TPS setting needs to be less than 0.56V on the 450 at idle, or else the signal "ATP" increases from 0% to 1% as though the throttle has been opened. The question is then, does it matter if the TPS is set higher ???
-Is there a problem with higher initial TPS settings???

Testing with an air/fuel gauge, the fueling is very consistent and nearly ideal when the completely backed-off idle speed screw results in 0.400V on the TPS (per the service manual). If the setting is higher, the results when riding makes a very rich zone just above idle and a brief flat-power zone at the same time. It can also result in a hunting/oscillating air/fuel mixture at idle.

Recommendation: Use the factory setting of 0.400V with idle screw backed off until the TPS voltage is unaffected by the screw, and keep the idle speed set to the factory spec for the ECU (1800-1900rpm for the 450/500 models). The TPS setting at idle should be no more than 0.55V on the 450/500 models as an estimate. With these settings and overall fueling correction of the tuner, the air/fuel mixture is consistent and makes for a great running combination IMHO

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Just got my tach to set the idle properly and I will reset the TPS to .601volts. I'll be sending out the ecu tomorrow. 

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