Technology ...

[Talking Heads]

The ECU doesn't increase rpm when the clutch is pulled in, it increases rpm as the clutch is let out and the engine comes under load.
The increase is only a couple of hundred rpm, in normal use if you didn't know it was there you wouldn't notice.
It only becomes apparent if you let the clutch out slowly with the throttle closed.

Originally Posted by Seeker

you're welcome. I couldn't find it at the time of the last post but here's a thread (from the Triumph 675 forum) quoting a Keihin document. Suzuki (and Triumph) use Keihin ECUs.


https://www.triumph675.net/forum/showthread.php?t=52296

I had a bit of spare time this afternoon due to having to wait for some bits and pieces to arrive at Screwfix, so I used it profitably by reading through the very useful links you sent me (well, I gave up on the first SVrider link after it degenerated into a ‘yes it is - no it isn’t’ argument). Most of the opinion seems to support the view that shorting out the clutch switch on pointy should make no difference to the ECU, the Triumph thread corroborates this.

The argument that the switch is connected to the ECU is pretty tenuous, the only electrical connection is to the negative return, which does run to the ECU as well as virtually every other component on the bike!

From my own experience and the lack of anything to show otherwise I’ve concluded there cannot be any causal connection between shorting the clutch switch and anything the ECU might do, and therefore only a coincidental link to a few owners who claim their bikes have been adversely affected. This morn I had been tempted to get a new switch and return my bike to standard, just to see if it made any difference. Then I thought of my 135.000 mile K6, which does not have a stalling problem, has really good performance and still returns just over 52 MPG (absolutely average for a K6) - and realised that would be an absolutely daft thing to do just to disprove something I was already convinced was not true anyway. This afternoon I’m being sensible again, and am not going to take my bike apart to see why it is going so well

I’ve enjoyed this little tangent Seeker, thank you for bringing it up and for taking so much time to look up the background. As they would say on that American TV programme: this myth has been busted!

Best wishes,

Alan


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[daktulos]

Originally Posted by Othen

The argument that the switch is connected to the ECU is pretty tenuous, the only electrical connection is to the neutral return, which does run to the ECU as well as virtually every other component on the bike!

Just out of curiosity (as I have a curvy) I had a look - to my eye, the right-hand connection to the clutch switch goes to just the starter relay and ECU. I've no idea what the ECU does with it, but to my eye it would definitely know when the clutch is engaged.

Originally Posted by daktulos

Just out of curiosity (as I have a curvy) I had a look - to my eye, the right-hand connection to the clutch switch goes to just the starter relay and ECU. I've no idea what the ECU does with it, but to my eye it would definitely know when the clutch is engaged.

Did you change your mind again about this one again daktulos? I’m pretty sure you said you had decided it did not pertain to a K6, but only to later models (perhaps I imagined that and it is the dementia setting in?).

My tired old eyes still can’t see an electrical connection between the clutch switch and the ECU (apart from the negative return path), but I have been intrigued enough to invest £8 in a new switch.

When it arrives I’ll return my bike back to standard and see if it makes one iota of difference (my feeling is it will make none whatsoever).

Watch this space...


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[Seeker]

the curvy doesn't have an ECU.

[Seeker]

Originally Posted by Othen

From my own experience and the lack of anything to show otherwise I’ve concluded there cannot be any causal connection between shorting the clutch switch and anything the ECU might do, and therefore only a coincidental link to a few owners who claim their bikes have been adversely affected.

glad you have solved it, now watch this:


https://www.youtube.com/watch?v=4_qnGJihHvM

[aesmith]

Most of the discussion about the clutch switch is to do with aftermarket levers that can't work the switch. It would be perfectly possible to modify the wiring so the ECU sensed the clutch switch but the starter circuit doesn't.

Originally Posted by Seeker

glad you have solved it, now watch this:


https://www.youtube.com/watch?v=4_qnGJihHvM

Thank you for that, quite an interesting video.

As you may have read above, I’m intrigued enough to have ordered a new clutch switch and will return the bike to standard when it arrives. I am still far from convinced on this matter (but it would be sort of cool if I’m wrong, it will mean my 135,000 mile bike will return better than average fuel consumption).

We’ll see when the switch arrives...but I’m not going to buy an oscilloscope to test it!


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[daktulos]

Originally Posted by Othen

Did you change your mind again about this one again daktulos? I’m pretty sure you said you had decided it did not pertain to a K6, but only to later models (perhaps I imagined that and it is the dementia setting in?)

I did - I realised I was looking at a K8 diagram, so edited it ... then found the K6 diagram and it's (different but) the same ... so edited the post back again.

I'm home now, and checked the Haynes diagrams, the black/yellow cable doesn't go anywhere except the starter relay and ECU on the K3 - K8s inclusive.

Originally Posted by daktulos

I did - I realised I was looking at a K8 diagram, so edited it ... then found the K6 diagram and it's (different but) the same ... so edited the post back again.



I'm home now, and checked the Haynes diagrams, the black/yellow cable doesn't go anywhere except the starter relay and ECU on the K3 - K8s inclusive.

Okay, thank you for that. My tired old eyes still can’t discern an electrical path to the ECU on the diagram, but no matter. I took the old (bypassed) switch off today, and can see why the original owner would have shorted it out, it has not worked for years. I’m curious to see what (assuming there is an electrical connection) effect the clutch switch might have on the ECU, so I’ve ordered a new one and will return my bike to standard once it arrives in the mail.

I’m still skeptical about the hypothesis, but I’ll be happy to be proven wrong as my high mileage K6 will be even better on fuel.


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