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Still not 100% confident.........


Welshguzzi

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I was about to suggest the same thing - simply un-plug the PC and go back to factory config ... bear in mind it will be different, but may indicate if your problem is with the PC (or not) ..?

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I didn't realise that you could just unplug it - my last bike was built in 1980 and the only electronic device was the ignition - FI and ECU's are a whole new world! Carbs are so easy to fix without a multimeter and software...........

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I hear you ... but FI has it's advantages (just like that new-fangled water-cooling thing) ...! The PC sits between the connector and ECU and essentially modifies the stock map - so don't forget to re-connect the main connector to the ECU (leaving the PC isolated) ... do this with the IGN switched off.

 

It may be that your PC was mapped to optimise for modifications (eg different exhaust system, air-box mods etc) and so factory config may not be ideal if so, but you shouldn't get the drop-out that you describe if the ECU is working normally.

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That would be the easiest thing to change: delete the PC and see what happens . . .

 

Otherwise, I would look for power dropping out from the ignition switch or the relays.

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Plus one on disconnecting the pc3.  I have one on mine and it did throw a wobbly last year (bike wouldn't rev past about 2k).  Unplugged and normal service was resumed.  Strangely, left it off for a while (months) and then re fitted and all was well again. As said, very easy to do, just unplug both plugs on the pc and plug the original bike loom plug back into the ecu.  As a precaution, disconnect the battery first.  You probably wouldn't cause any harm ,but ecus don't tend to like power surges.  Once you have the bike back to standard it'll be much easier to diagnose any other issues as a pc map can help to disguise symptoms.  Think of the pc as a "fine tuning" unit.

 

I'd go with a valve clearance check, tps setup, followed by throttle body balance and idle mixture setup in that order, then see where you go from there.  You may have already done a lot of that, but I'd go through and double check.  My gut feeling is that it will be tps (incorrectly set of failing), lean running due to fuel map being incorrect (unplugging pc should show this one up) or maybe valve clearance closing as the engine gets warm.

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Just a quick question about valve clearances: I know that there's some debate about what is best and that there is some discrepancy between the factory recommended and ?Raceco?. What are people using? In millimetres if possible!

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I run mine at standard, but err on the side of loose rather than tight.  However, if it gets really hot in traffic, it does sometimes start to misfire a little when set to standard.   I tried the raceco settings and that was improved, but it was quite noisy.  Other than that, I didn't notice any benefit.  I could see how a temp related valve clearance problem might cause what you are experiencing, but that's unlikely at 70 mph.  I'd still put money on the pc3 causing issues, but that's an easy one to diagnose.

 

If it's of any help, I had a failing tps on my other bike (TDM 900) which had similar symptoms to yours.  It was changed by Yamaha as a recall as the issue affected a number of bikes in the range.  Bad batch, I guess.  

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Just a quick question about valve clearances: I know that there's some debate about what is best and that there is some discrepancy between the factory recommended and ?Raceco?. What are people using? In millimetres if possible!

"World specs" are 0,15mm/0,20mm (0.006"/0.008")

 

Some US specs were tighter and "Raceco" specs are looser.

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New boots also installed - original ones were both split.

 

The break downs were both the same - sudden loss of power (first time in lane 2 on a motorway) accompanied by prolific back firing almost like it was dropping onto 1 cylinder and eventually none.

 

I don't want to go through that again. ! ! I tried isolating the neutral/side stand switch with no improvement, so it probably isn't that.

How would you like to cut the potential problems in half?

 

I keep telling guys (few listen) to wire a small 12 Volt lamp to the petcock fuse (even if you have a mechanical one).

This will tell you instantly if the problem is before the ECU or part of the ECU wiring.

If the light so much as flickers its the ignition switch, stand relay, kill switch battery connection or something before the fuel petcock

If the light does not flicker but the bike starts to miss, backfire or misbehave in some other way it's something after the petcock fuse, ECU, fuel pump, Ignition, ignition sensors etc.

(already your little light has eliminated half the potential causes)

 

A 12 Volt LED strapped to the bars would be best, that way you can glance at it with any sign of a miss.

 

I will send you a PM

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I might have something useful for you to try... although I thought the exorcism had potential...  :grin: ...and wasn't that a nice old Norton?

 

This is starting to sound similar to a problem I had on my BMW R1100RT. I had lost power suddenly a few times, but with this additional symptom - sometimes would not start. I did not have the backfiring as you described.

 

Loooonnnngggg time later, I finally figured it out. The problem was the engine kill switch. Now I realize that's a totally different bike (mit Hängetitten & carburetors), but if you've tried so many other things, you might as well take your kill switch apart, clean and inspect it really well, and put it back together. I don't know what's in the Guzzi's switch, but a tiny spring had gone missing (assumed broken and wriggled out somehow) from my BMW's switch - that's what made it occasionally lose contact. Sometimes it would go in fits - imagine turning your kill switch on and off really fast while riding. 

 

Like you, I had lost confidence in the bike. After the repair, no more problems - years of not trusting that bike, all for a spring that could fit in a watch.

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Check the resistance of all the switches etc, they should read low and be consistent every time they are operated, a variation in resistance points to dirty contacts (hard grease holding them apart or melted plastic letting the contact move back out of reach) I doubt it's a broken wire at the switch but give those a wriggle just in case.

 

pdf.gif  Test Point Layout.pdf   Pull all the relays and fuses out first. (I'm fairly certain all the spine frames are similar)

 

I have found the wiring around the ECU is very robust, it's usually something before there. The petcock fuse (TP-d) is like a bottleneck, it

will drop off if any of the switches are bad bumping the ECU and make the little light flicker.

I know it's high tech but it's not bad to have a permanent light under the seat at that point, always available if needed.

Don't try to look under the seat while riding though, it'll give you a crick in the neck  :oldgit:

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Check the resistance of all the switches etc, they should read low and be consistent every time they are operated, a variation in resistance points to dirty contacts (hard grease holding them apart or melted plastic letting the contact move back out of reach) I doubt it's a broken wire at the switch but give those a wriggle just in case.

 

pdf.gif  Test Point Layout.pdf   Pull all the relays and fuses out first. (I'm fairly certain all the spine frames are similar)

 

I have found the wiring around the ECU is very robust, it's usually something before there. The petcock fuse (TP-d) is like a bottleneck, it

will drop off if any of the switches are bad bumping the ECU and make the little light flicker.

I know it's high tech but it's not bad to have a permanent light under the seat at that point, always available if needed.

Don't try to look under the seat while riding though, it'll give you a crick in the neck  :oldgit:

Roy, you mention "flicker" if before the fuse, and "misbehaves" if its after.  Do you mean while idling or running?  And can you descrbie "misbehave (only as it pertains to this issue... lol)?

 

My .02 is still on the PC--I had a similar issue on a TL1000R and removing the PCII fixed it.  I have a hiccup now, right at 3k, but I don't even notice it much anymore.  I might take my own advice at some point and disconnect the PCIII...  It seems redundant to have a PCIII AND a Kit ECU...

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Flicker as in get bright, dull, go off in quick succession in an erratic fashion As a candle in the wind.

 

Misbehave as in stall, backfire, miss cough fart and generally run in a disappointing way

 

The light doesn't fix anything it just divides all the possible problems in two helping you identify where it is or isn't

 

Scuds faulty kill switch would have shown up instantly as a light going on and off i.e. flickering. this would have allowed him to focus on just a few possible faults between the battery and the petcock. I have a permanent light on mine, it's come in handy several times.

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