Surging at 3-4k RPM

[the slow heart]

Keep it up man, the bike just gets better 

Hope spark plugs inspection won't raise more issues like piston ring or valve guide leaks, beware how much you torque them in thereafter. Are the plugs Denso, or NGK equivalent? In my location NGK cheap replicas are more common.

If the lambda is not working properly, it may override proper iacv co setting. On the safe side you better test it with a meter, wash it after gasoline soaking. You could also test unplug it from the loom to simulate open loop system and load the 9891 map. After the test load back 9892 and plug the sensor.

Pump priming may be less pressure due to less voltage. More important is when bike is running, voltage high ( how much is it at idle actually ? ). Anyway you are within 10% of the 3 bar requirement.

Might be the questioned one way valve is within the iacv itself, get it off and mouth blow it both sides to check whether it is one or two way open?

[the slow heart]

Any chance crank shaft position sensor to be disturbed? It is well exposed during clutch/ valve train works.

[Flyingwombat]

Cheers man,

Plugs are NGK probably about 300 miles through them, although I will need to double check as apparently fakes do exist and they were mail order...

I haven't done the valves or clutch, so the only way that the Crankshaft Position Sensor could be off would be some slippage.

The valve clearances are due a service, but I want to get it going again first. Will try some of these lambda sensor fixes and blow the otherway into the IACV.

[Flyingwombat]

Spark plugs were black with carbon! Will be cleaning or renewing before carrying on. Although I am not sure that this is the main issue because it was still running with -ve adjustment on the LTFT.

[Flyingwombat]

So this is a little funny, and slightly embarrassing.

It turns out that the lambda sensor on my exhaust is not plugged in, and never has been. The cat on the exhaust must have got replaced after an accident I'm guessing from a scrapped bike. So this would explain a lot.

I have loaded the 9891 map and it's working again. I have also replaced the spark plugs due to the fouling, and set all the trims back to 0.

I am back to square 1. The bike is working, throttle bodies are balanced but it's still surging.

Looking at the pump pressure this seems fine.

What I have noticed is that there appears to be some backfiring, into cylinder 2 which is not noticeable when throttle is open, but when it is closed you can hear a hiss and see a small flash in throttle body 2, there is no popping in throttle body 2 when the throttle valves are open. I am slightly concerned that I can see a flash in body 2, as this means it's not fully air tight when closed, although it appears balanced with the throttle touching the motion limiting screw.

So here's some numbers at idle @1180 RPM
Ignition Timing is at 4.5deg target dwell times of 1.8, 1.8, 1.9ms and Ignition Pulse times of 1.801, 1.696 and 1.740ms(in 1,2,3 order)

@1260 RPM
Ignition Timing is at 5.5deg target dwell times of 1.9, 1.8, 1.8ms and Ignition Pulse times of 1.798, 1.737 and 1.904ms(in 1,2,3 order)

The valve shims do need to be done too at some point, but I am wondering if my injector in cylinder 2 is leaking slightly.

[the slow heart]

We all have our funny and unforgettable memories from the garage 

This manifold backfire suggests inlet valve on no.2 is not completely closing and compression phase pumps back air/fuel mixture in the manifold, exploding with some correlation to no.2 firing time. It is serious suspicion that could lead to valve/piston further complications. I would do valve clearances first and check compression after. Then if no.2 shows lower pressure, head has to go off and valve seat potential damage cleared out until it is withing recoverable limits. Fiddling with fuel mapping should be no priority in such situation 

[Flyingwombat]

Oh good. I'll get on with it then.

Hopefully no lasting damage.

[Flyingwombat]

Latest Update - Shim clearances measured!

Cylinder 1 - Intake - 1x gap too small
All other intake gaps are fine
Cylinder 2 Exhaust - 2x gaps too large (marginally)
All other exhaust gaps are fine

This seems OK but it does not seem to explain ignition in cylinder 2 throttle body.

[the slow heart]

Maybe the compression test would clear the picture. Anyway you could check timing and reshim the marginal valves.

[Flyingwombat]

Shims changed, compression test tomorrow.

[London_Phil]

I admire your determination. I really hope you get this sorted.

[Flyingwombat]

After shimming I have cold compression of 165, 170, 158 PSI. Cannot see in the manual what it should be hot or cold...

[Flyingwombat]

So I didn't type this out because I was desperately trying to fix her in order to ride her to the ABR festival... Unfortunately this did not work out and she remains in pieces.

So the update.

- Putting her back together she was idling better.
- When the engine got hot I saw ignition in throttle body 2.
- I replaced TB2 injector with a salvaged one.
- Then once the engine was hot I saw ignition in TB1.
- I replaced injector in TB1 with another salvaged one but TB1 is still igniting.
- I then re-checked the TPS function, the TPS voltage shown on TuneECU remains constant during fluctuations of RPM, and increases continuously as the throttle is twisted.

I still need to do a hot compression test.

[HiYo Silver]

It's been said before, but I really admire your persistance in getting this problem identified and solved.   For an absolute newbie like me, it's like an episode from Star Trek, where the engineers are saying "We'll have to re-phase the deflector dish and route the plasma through the Jeffries tube....."

[Flyingwombat]

Hey dude, I'm just an engineer who cares about bringing my dads bike to running order again. I'm as lost as you just a few months past the event horizon...