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Why is EXC running too lean again?

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I have a 2018 KTM exc 500 with the vortex, aftermarket pipe, reed valve removed and a Uni filter. I did the emissions block off which stopped the backfiring and missing. It has run great for months yet recently the backfiring on deceleration and missing just off idle has started again. 

I double checked to make sure that the emission hose by the spark plug is blocked off and it is. Do you have any idea what might be causing this backfiring and missing just off of idle?

Thank you in advance  

 

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Hum you still have emission hoses. Double check your block off. I got rid of all that stuff and never had a issue. 

Its likely not valves but you can check them and don’t touch the tps if it hasn’t been messed with. 

Edited by StevetheSnake

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dump the plumbing ! save it for the guy who buys your bike "used one owner"

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5 hours ago, Bret Bouer said:

I have a 2018 KTM exc 500 with the vortex, aftermarket pipe, reed valve removed and a Uni filter. I did the emissions block off which stopped the backfiring and missing. It has run great for months yet recently the backfiring on deceleration and missing just off idle has started again. 

I double checked to make sure that the emission hose by the spark plug is blocked off and it is. Do you have any idea what might be causing this backfiring and missing just off of idle?

Thank you in advance  

 

I had this happen. I double checked the bolt that blocked off the air injection for that smog thing and found that it had come a little loose letting air in. I did some hightemp sealer and a little loctite and it's been great since. Check that you're all sealed off. Sounds like air is getting in.

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8 hours ago, Bret Bouer said:

I have a 2018 KTM exc 500 with the vortex, aftermarket pipe, reed valve removed and a Uni filter. I did the emissions block off which stopped the backfiring and missing. It has run great for months yet recently the backfiring on deceleration and missing just off idle has started again. 

I double checked to make sure that the emission hose by the spark plug is blocked off and it is. Do you have any idea what might be causing this backfiring and missing just off of idle?

Thank you in advance  

 

Check your fuel pressure. I’m willing to bet your fuel pump is slowly dying. It happened to mine. 2017.

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19 hours ago, sixdaysoffun said:

Did you check your valves and tps voltage

I have adjusted the valves recently and it is my understanding that the 2018 with the Vortex doesn't need the TPS voltage checked.

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12 hours ago, Pipester said:

Check your fuel pressure. I’m willing to bet your fuel pump is slowly dying. It happened to mine. 2017.

I just brought it into the shop and their first guess was the intank fuel filter was causing the problem. 

15 hours ago, phatfos1 said:

I had this happen. I double checked the bolt that blocked off the air injection for that smog thing and found that it had come a little loose letting air in. I did some hightemp sealer and a little loctite and it's been great since. Check that you're all sealed off. Sounds like air is getting in.

I double checked that first thing. Good idea. 

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Bret, have you tried to run the 'initialization' cycle after making changes?

Used for big elevation changes or engine mods. Start & run at idle. Let it run til 170+ degrees as stated in my shop manual, shut it off and it's updated. The vid states 200 degrees at several minutes run time.

 https://www.youtube.com/watch?v=PbHJihxMsU0

Edited by Burnrider
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