My 1998 ST2 has just started exhibiting some strange symptoms when starting up (hot or cold). When I press the start button sometimes the starter motor tries to start turning the engine over but can't - it seems to turn the engine very slightly then sticks. If I try again a few times it will usually get it started on the 3rd attempt but in the past it has always fired up on the first press. Also sometimes I press and release the starter button and the engine does not fire up but the starter keeps turning over even if I turn off the engine run switch and turn off the key. The only way to stop this is to turn the engine back on and when it eventually fires up if I then turn off it will have stopped cranking (usually). Battery voltage is 12.7 with no load, 12.4 with engine and headlights on but engine not running, with the engine running it's at 13.5 at tickover and drops to 13.2 if I rev it. the battery seems to hold charge OK over several days if nothing is switched on. When starting, the voltage drops to about 5-6v if the starter sticks and about 8 if it's cranking over. My thoughts are maybe the solenoid because I can't see how else the starter would keep cranking with everything switched off but that wouldn't explain why it can't turn the engine over. Also not sure about the battery voltage when revving it up, is 13.2 about right? Any ideas/thoughts please? Ta Jim
The sprag clutch won't keep it cranking. The relays aren't involved with the starter circuit. Change the solenoid. They're not expensive.
“When starting, the voltage drops to about 5-6v if the starter sticks and about 8 if it's cranking over.” Not sure what you’re saying here whether it drops this amount or reads this amount but either way that ain’t right.
about 2 and a half years. I think the next step it to try shorting the solenoid contacts to see if it then cranks normally - if so I'll swap the solenoid. If not I'll try a jump pack to rule out the battery and then I guess it's a new starter motor.
Can you get access to a known good motorcycle battery? Eliminate the battery as the problem, fit the good one, does it cure problem. Starter relays are not too expensive to replace. A failing battery is unlikely to make the starter crank with the ignition off by itself. However, a weak battery can cause low voltage and relay or solenoid chatter, leading to electrical arcing. Over time, that arcing can damage or weld the contacts, resulting in an intermittent or stuck starter relay or starter solenoid. In that case, the battery is an indirect contributing factor, while the damaged relay or solenoid is the actual cause of the unwanted starter engagement.
Not bike related, but I had a similar problem with some older cars. I used to whack the starter solenoid with a lump of wood and all was hunky doory.
Ducati newbie however possibly starter solenoid sticking The low voltage cab cause contacts to stick/weld together either permanently or temporarily 8v imho unlikely to be enough for injectors to function properly
If the starter motor continues spinning after switching off the ignition then the solenoid contacts have spot welded. It may have originally began with a sticking starter button. Regardless, the solenoid contacts are probably now knackered, with increased resistance, though we are talking fractions of an ohm. Resistance + high starting current => voltage drop and more heat. Replace the solenoid but before trying it check that your starter button isn't physically sticking in when you press it.
Sounds like PeteW could well be right. Also I’d recommend fitting new starter cables. I fitted them to my ST4 and it transformed starting from long slow and laboured, sometimes taking several attempts as you described to instantaneous. Exact Start do them. They’re thicker cables made specifically to length for your model. You’ll need the ES10 Ducati. https://www.ducati.tech/exact-start-cables-model-fitment-guide Worked a treat for me.
I suspect there are at least 2 things going on here, possibly 3. 1. You’ve a suspect starter solenoid as suggested by others - cheap and easy to replace, it doesn’t need to be an OEM one just one with the correct configuration of connections and rating. 2. The fact the battery voltage drops to 5-6V when the starter tries to engage but doesn’t turn the engine over implies to me the starter motor itself is suspect. It may just need new contact brushes internally or just a strip & clean but I suspect the motor is trying to turn but isn’t and is demanding more current from the battery which is causing the massive voltage drop. 3. 13.2V will be barely recharging the battery so the r/r may be on the way out. However, don’t suspect that too quickly as ST2s have notoriously poor charging systems, especially if yours is the single phase version - ie only 2 yellow wires coming from the stator.
