New S4 owner from Northern Ireland

[350TSS]

Before you change the discs try cleaning the bobbins. Brake cleaner them, then wedge a screwdriver into them and get them revolving freely, maybe the merest hint of lubricant. Once they are all free take the bike for what Mr. Gasa calls an Italian tune-up. Get up to a decent speed on an empty bit of road and apply the brakes lightly at first and progressively harder over the next few runs until you are almost getting the rear wheel to lift. This will wipe clean any surface corrosion/ chemical contamination off the discs. At the end of the exercise, you might find the brakes work remarkably well with no judder. Doesn't cost anything and is quite good fun

[Mr Gazza]

Don't be tempted to lubricate the bobbins in any way, anything you use will be heading straight for the friction area of the disc at speed!
The discs and pads must be cleaned as well as possible with clutch and brake cleaner before trying to condition them with the heavy braking exercise.
The secret is to give the brake a firm, even, LONG application to get it warm and apply plenty of friction. A good head of speed helps lengthen the braking time. Let the brakes off gently as speed fades and try again. It's important not to come squealing to a halt as the idea is to warm the discs evenly and let them cool evenly with the pads off and the wheel still turning.

Unfortunately this method will not do any good if your discs are actually warped, the only way to find that out is with a dial gauge.

If your brakes are juddering I suspect that it is warped disc(s) as the surface conditioning syndrome tends to manifest at walking speed in the final yards of braking to a halt, as a sort of on/off or pulsing feeling.

Definitely worth trying an Italian tune up though...

[Rostrumorhospit]

Thanks for the tip 350TSS, will definitely try that before shelling out a few hundred quid on discs, just to clarify, when you say bobbins, that is the bush type article's that allow the disc to float?
Thanks
Davey

[Rostrumorhospit]

Appreciate the help MR Gazza, you got your reply in while I was writting mine, will stay away from the lubricant, but give them a good clean and free up, see how it goes.
Cheers
Davey

[jerry]

If u need discs dont waste money on Brembo ones ,, Galfer , EBC or Arashi all good and much cheaper and longer lasting

[Rostrumorhospit]

Tried the new fuel filter but revving out just the same, although it was stinkin so needed done, also tried new plugs but with no noticeable difference.

I will have a go at most stuff but have always struggled with electrical issues, gonna leave it with a local mechanic, see if he can eliminate some of the electrical components, fingers crossed and thanks for all the advice.
Davey

[Darren69]

Do you have any engine management errors, is the yellow engine system error light on the dash on or comes on at all? I'm thinking if it were a crank sensor issue then it would light (as I had an intermittent failure of that sensor) but then it would reset the next time.

I don't know the exact symptoms if you get some ECU failures, but again I would expect it to light up if there was a problem with any of the ECU Canbus sensors or the ECU itself had failed. I don't know what else to suggest I'm afraid. Was it running OK when you first bought it and this is something that has occurred since? Maybe the previous owner could shed some light on it with respect to the history of the bike? If its not electrical or injector related then it still suggests fuel supply or fuel pressure to me. Maybe the fuel pump is failing? Are you able to check the fuel pressiure? There is a pressure regulator so that could be something else to check.

[Rostrumorhospit]

The bike was not running when I bought it, but that was the sprag clutch, I replaced it and has been starting on the button from then.
As far as I'm aware the bike was running ok prior to the starting issue.
The dash is an analogue dash with just the 2 dials and a few lights but no engine management light, although there is a yellow light for the key code, not sure if that can alert to any issues but at the minute it just flashes when the key is removed and goes out when the ignition is turned on.
Thanks
Davey

[Darren69]

Could maybe be a TPS issue if it is not working past a certain point/voltage?

[Darren69]

Oh, I thought the analogue clocks still had the canbus light, maybe not? Sorry, I never had one. Then it must be an '01 module. If that's the case then jpdiag or something similar would be needed to query if there are any error codes. There are a couple of versions floating about (Guzzi Diag/JP Diag/Duc Diag) etc which are free to download. You just need the right lead to connect it up to the bike. Luddite?

[Darren69]

Your air intakes and throttle bodies air is all clear, nothing blocking it. Without the air filter/air box lid?

[Rostrumorhospit]

Yes, the air box has the top cut of it and I fitted a new filter, all looks good, I believe that is a popular mod to the air box.
Thanks
Davey

[Darren69]

Yea, no air supply issues then. It still sounds like a fuel supply issue and the regulator is there in case of over pressure so I don't think it will be that, and if you have blocked injectors or duff coils it will be dropping onto one cylinder so you would just lose power but should still rev out.

The only other thing that I can think of is the valve adjustment being out but I doubt that would have to be a long way out to have such a drastic effect. You would lose power sure, but the engine would probably explode before getting that bad. It's like it's only breathing through 1 valve instead of 2.

You sir have a 4V Ducati that thinks its a 2V. Even the 2V will rev up past 8/9K but will just not make any more power past 7K.

[Darren69]

I wouldn't rule out an ECU or TPS failure as it sounds like it could have been like that before you bought it and you only have the sellers word that it was running ok before. i giuess it would be a good time to call in an expert if you know one, it's usually something fairly simple but not fairly cheap to fix. Presumably you got the bike cheap because it was a non-runner, so you should still be quids (euros) in? Most things are about 100 bucks to fix plus labour.

[Rostrumorhospit]

My gut feeling is lack of fuel, left the bike with the mechanic last night, he never really said anything in particular he reckoned it would be, but would hopefully have a better idea once he had it out for a run, fingers crossed he can find something.
Thanks again for your help.
Davey