[Bmadd34]

https://www.youtube.com/watch?v=TiX8oFtYZls

TPS output voltage is set at 0.6 +/- 0.2.

If you set the TPS voltage closer to 0.4V the bike runs weaker, closer to 0.8V and it runs richer.  IIRC  0.72V is the preferred powaaarh option,  with 0.61Volts being the optimal setting for the system itself.

That's a good video, but only it shows how to test the TPS. How is it adjusted?

[Carlsberg Wordsworth]

You'll need to slacken the screw then adjust very minutely to adjust the voltage up or down then tighten when the meter shows your required value.


I think it's the screw that hold it from memory. It's here somewhere on the forum though showing a pic if memory serves. Go gently!

[longstrokeclassic]

On the B5 the locking screw access is hindered by the battery which doesn’t require removal or disconnection - just repositioning after unclipping the rubber retaining straps if using an L shaped key . The TPS Screw has a Torx head so you can’t tamper with it 

[Bmadd34]

So, just to clarify, there is a torx screw that needs turning from the left side under the seat, behind the battery. No need to do this until the o2 sensor is bypassed. Correct?

[longstrokeclassic]

The torx screw locks the TPS unit into place by screwing into the very soft metal of the injector body.
 The benefits of different fuelling after TPS adjustment can be appreciated immediately irrespective of if or when an O2 sensor is or isn’t fitted.

[Youngan]

I’m resurrecting this old thread to add my own experiences/discoveries.  This is in case it’s useful to someone going down the same path, as well as to double-check what I’ve done against the excellent minds here in case I’ve misunderstood something.

On my 2011 Bullet 500 EFI E5, I had many of the same O2 sensor issues others describe early in this thread: 

Uneven idle
Hunting at low revs/low speed
Stalling
Running especially poorly in the half-warmed-up phase, perhaps as it was transitioning between open and closed loop.

I also experienced, as the most significant symptom, severe spark plug carbon fouling, such that I had to replace it with a new one quite frequently, like every several days, just to keep it running.  It doesn’t help that most of my riding is, by necessity, short trips at very low speeds. 

After much testing of sensor output, etc., I ended up disconnecting the O2 sensor and running it that way.  The bike instantly ran better, with all the above symptoms eliminated.  I ran it that way for many weeks, with no running problems at all, no need to replace the spark plug, and good spark plug color.

So then I wanted to keep it that way, but find a way to extinguish the engine light, while leaving it functional to indicate other faults.  I looked into the Greek eliminator plug mentioned in the thread, but shipping was an issue to my rural area of Alaska.  I started down the road of trying the simple resistor installation, of which one poster gave a hand drawing.  He only showed it on the sensor circuit (the one going to ECU terminal 7) so I wondered it would work; if the ECU looked at just the sensor circuit for faults, or if it also looked at the O2 heater circuit.  I removed the four wires from the sensor plug, and tried plugging in just one circuit (sensor or heater) to the harness plug at a time, to see which would keep the light extinguished, or if it needed to see both.  To my surprise, all it needed to extinguish the light was the heater circuit!  So in the end, I put all the sensor wires back in the plug except the black wire, which is the one that feeds a voltage signal to ECU terminal 7.  This keeps the Engine light off, and the ECU in open loop, just following the pre-programmed map. 

To be clear, the O2 sensor is still sitting in the exhaust, getting heated by the ECU, and creating a voltage signal that goes nowhere, due to the one disconnected wire.  Seems like the simplest way to fix this whole problem.  No resistor, no eliminator.

One final point of clarification:  The wire colors can be a point of confusion, as they change going from the sensor plug into the harness plug.  Black on the sensor side is white on the harness side.  Grey on sensor side is black on harness side.  The two heater wires are white on the sensor side; on the harness side, one is white, the other is red. 

What am I missing?

[Youngan]

Well, that was a short-lived victory.  A test ride reveals that the light comes on after about two minutes and ten seconds of engine run time.  This is true every time, regardless of engine temp, speed, rpm, etc.  Behaves the same just sitting and idling.  So there must be a timer in the ECU that keeps it from looking at the O2 voltage signal for a fault until that time expires. 

Guess I need to try the resistor after all.  Or the eliminator, if I can get one shipped here.

[Roadie]

Maybe just lucky but the mapping on mine is the smoothest fuel injected vehicle I've ever had. This morning I was trickling along on zero throttle in very slippery mud just using the tiniest throttle openings and just smooth running. Perfect

[Ove]

I suffer surging at light throttle and a very snatchy throttle. To be honest, I was absently riding round this, as I suffered the same on my main, modern, touring bike. Looking back, I think I've be riding round this behaviour for some years. However, last year I bought a 1975 850 Norton Commando. Then I realised how good a throttle can be and how I'd been desensitised by progressive emissions regulations on my bikes.

I replaced my touring bike late last year. I spent multiple hours on test bikes, to find one that behaved well on the throttle (Kawasaki ninja 1000sx). So it is possible with EFI.

Last weekend I made a shortcut when out on my 500 Trials Replica. At one point I was up on the pegs over some ruts. The throttle snatchiness had me pogoing back and forth on the pegs. I gave up and slowed to a crawl. I want to keep the Enfield though. So, I will first try the eliminator (ordered today). If that doesn't work, or I don't like the look of the plugs, I'll try the booster plug. If that doesn't work,  it's either a power commander (but not cheap), or regrettably, goodbye Enfield. I really hope the eliminator cracks it.

[Ove]

The O2 eliminator arrived this morning. Took me longer to read the 1/2 page instructions than it it took to fit it. For the time being, I left the sensor on the exhaust, disconnected and still clipped to the frame.

The 'eliminator' has totally removed the hunting. It has improved, but not removed the snatch, when rolling on from no throttle. I am able to ride standing on the pegs, but it can still be a little jerky. So, 10/10 for removing the hunting. 5/10 for roll on. However, a side effect seems to be holding on to revs when throttle off and clutch in. Probably ticking over at c.1800rpm until I blip the throttle and it settles back down. Weird. But, on the whole, easily worth £14 and I'll keep it on the bike. No engine warning light.

I wonder if I might need to give the injectors a clean? 3,500 miles in 30 months, so a bit of standing around with E5 fuel. How easy is it?

[GlennF]

I wonder if I might need to give the injectors a clean? 3,500 miles in 30 months, so a bit of standing around with E5 fuel. How easy is it?

You could try a bit of seafoam in the fuel, or maybe the type you spray into the air intake (never tried it).

To clean them manually you need to remove the injector from the bike and spray carb/injector cleaner through them.

[Boxerman]

I wonder if I might need to give the injectors a clean? 3,500 miles in 30 months, so a bit of standing around with E5 fuel. How easy is it?

I have on a couple of occasions traced low speed jerkinnes / misfire down to very, very fine deposits on the filter screen of the injector, its like dust really and its possible that it only applies to my bike?
Worth a look though?
Your bike is a lot younger than mine, but on mine, I remove the injector, pull the brass hose adaptor off the injector and blast the filter screen with carb cleaner.

Frank