No fool by far Costas. If I could speak any other language than 'stoopid' I still wouldn't be as clever as you!
It is an easy mistake to make especially in a foreign (to you) language. Technical Greek must be even more unfathomable than real Greek.
I just felt it was important to let folks know which bits are changeable and which are not and which can cause the problems you had. Not to mention that I thought that a set of throttle bodies was cheap even in Euros!!!
So, back to Max's original problem.
Things that can cause slow and stumbling idle:
One or more ignition coils breaking down. Highly likely, quite common.
They can start to fail at high rpm or at low rpm. Either way, they can then perform perfectly at the other end of the rpm scale and can also fail and work perfectly on an intermittent basis. If one coil fails or is playing up, I would always change all four at about £70 each plus labour, but the labour involves draining the coolant, removing the radiator, changing the coils and refilling the cooling system. All in all it is a big labour bill if you are paying someone else to do it. The labour, whether you are paying someone else to do it or not, is always more expensive than the parts with these things.
One or more injectors failing. Highly likely, quite common.
Injectors normally 'stick', either open or closed or sometimes they can 'stick for a while' either open or closed. When they fail completely, they normally fail closed in that it is the electrical coil in the injector that activates the 'valve' which breaks down. Sometimes it can be the valve that fails, but this is not normal in my experience.
Idle Control Valve sticking/failing. Likely, very common.
The idle control valve (ICV), is a mechanical sliding valve located in the bottom of the airbox. It has an electrical connection from the ECU and four (or five depending on territory) rubber pipes connected to the inlet manifold below, or downstream, of the throttle butterflies. The ICV contains a piston which is driven up or down a shaft, so allowing more or less air to bleed into the engine so effectively altering the mixture and acting like a choke. This piston is driven by a stepper motor which can be heard ackling when the ignition is first turned on and before the engine starts.
The idle control valve is controlled by the ECU and is used to bleed air from the airbox, past the butterflies in the throttle bodies to increase the idle speed under certain conditions. The system is 'open loop'. The ECU thinks, at this air temperature and engine temperature at this engine speed, I want to increase or decrease the idle. It tells the ICV to go to 'this' position, starting from zero. However, being open loop, the ECU has no idea from where the ICV is actually starting its movement; so when it moves, it may or may not have the result that the ECU wants. The ECU gets confused by the result and all hell breaks loose.
In early 1200 bikes, the airbox could warp caused by the heat from the engine. This then caused the ICV to stick. When this happened, the idle could rise to as much as 3,000 rpm causing huge problems when trundling to a halt as the bike would just continue powering forward.
In addition, the ICV could stick closed, which could cause the bike to stall when coming to a halt. This caused lots of 'accidents' at T junctions and so on when the bike didn't pick up as you turned out and as a result there were lots of dropped bikes in the early days.
The fix was a new design of airbox and ICV and together with a software update, this fixed this specific problem for the 1200's.
(In my case, the bike bucked and heaved so much at low speed, say 10-20 mph in first or second gear, that my helmet would hit the edge of the windshield. The later airbox and ICV fixed this completely.)
All 1300's have the later airbox and ICV but the problem of sticking ICV's still persists, even to this day on brand new bikes and most dealers (in the UK) know how to diagnose and fix the problem.
Fuel Pressure Relief Valve. Not unknown, unlikely.
This sits on the fuel rail upstream of the injectors and does what it says on the tin. It regulates the fuel pressure to the injectors. If this starts to stick, then fuel to the engine can get restricted with resultant problems in engine running. This normally causes problems at high engine speeds rather than low ones.
Throttle Position Sensor failing or loose. Not likely, but known to happen.
The Throttle Position Sensor (TPS) sits on the right hand end of the throttle butterfly shaft and tells the ECU what position the throttle butterfly shaft is in percentage terms. Closed is 0%, wide open throttles are 100%.
The TPS, which is a variable resistor, itself can fail (unlikely, but not unheard of), but more likely it can come loose. It is held in place with two bolts which have been know to work loose causing mayhem. The ECU gets the wrong throttle position information and then tells the injectors to do the wrong thing to correct it.
Spark Plugs breaking down. Common at high mileages.
Any or all of the spark plugs can start to fail, either at low or high rpm. Normally plugs break down at high work load but they are fickle things.
Take your pick from any or all of the above as a good starting point!Any half-decent, modern bike shop should be able to diagnose and fix all of the above. All modern bikes (and cars) have a very similar system and it is all 'normal' stuff! A main dealer should go straight to the problem if it works through the diagnostics methodically. Tom's 'fluid on the exhaust pipe' trick shows which cylinders are affected and the diagnostic kit in dealers should show the same stuff.
Brian (who says there is no excuse, but hey ho
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