ER6N running rough below 3K rpm

[andy_uk]

I have a 2006 ER6N approx 36K miles
Over the last few weeks it has started running very rough below 3K rpm (no power, spluttering, surging, backfiring etc). While ticking over the revs fluctuate between 1K and 1.3K
Someone suggested it could be the TPS so I attempted to adjust it without using any test gear!! (yeah, I know...bad idea)
After adjusting it, it ran a lot better. Unfortunately the side effect to this was the fuel economy dropped drastically (from 130 miles per tank to 75 miles per tank...😳)
I have since set the TPS back near to stock settings (1.01v at idle). The bike then ran fine for a couple of days but then reverted to the poor running again and is gradually getting worse.
The plugs were changed 3 months ago at its last service, along with the usual oil & filter change, air filter clean etc.
The only modification is that the exhaust system is from a 2010 model.
Any ideas?
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Aprilia Classic 125, GS500E, ER5-A1, ER5-C4, ER6 & an XJ6 project frame...

[jaffa90]

I would further test the T.P.S. through the rev / position ranges.
Sounds worn out up to 3,000rpm but other sensors could be involve.

[jaffa90]

""" The only modification is that the exhaust system is from a 2010 model."""

Did both exhausts have a lambda sensor fitted or maybe bypassed.

[andy_uk]

The original (stubby) exhaust didn't have one (bypass plug was fitted). The new one did have one and it is connected.
It was working fine after I fitted the new exhaust a few months ago.
It's only over the last few weeks it's been playing up.
I'm going to check the voltages through the whole throttle movement today and see if the readings look dodgy.
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Aprilia Classic 125, GS500E, ER5-A1, ER5-C4, ER6 & an XJ6 project frame...

[Robby]

Try disconnecting the lambda sensor and using your bypass plug. If it starts behaving, your problem is the lambda sensor.

If the exhaust and sensor are 2nd hand, then the sensor could have failed. They don't seem to like being disturbed.

[andy_uk]

So...I've checked the TPS and the readings are pretty consistent when twisting the throttle.
I also increased the output voltage slightly from 1.01v to 1.13v which has helped a bit.

I will put the lambda bypass plug back in and see if that makes a difference.
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Aprilia Classic 125, GS500E, ER5-A1, ER5-C4, ER6 & an XJ6 project frame...

[andy_uk]

Okay, so I tried the lambda bypass plug and it made no difference unfortunately.
Here's a link to a short video of it running after being warmed up.
For the first few seconds it's just on tickover, then I increased the revs slightly which is when it starts popping etc.
https://photos.app.goo.gl/mNM7fFr5SQ5opB779
Apologies for the crap sound quality...
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Aprilia Classic 125, GS500E, ER5-A1, ER5-C4, ER6 & an XJ6 project frame...

[Kawasaki Jimbo]

Faulty ignition coil? They seem to have various failure modes and testing can be inconclusive so personally I'd gamble on a replacement. (eBay?)

[andy_uk]

[jaffa90]

Well if the tickover / idle is ok and ok above 3,000rpm then i can only think of a too lean fuel mixture in them low rev ranges.
When were the fuel injectors last cleaned ?

[andy_uk]