Reminds me when my 1985 R80 wouldn't start. Tried all the rider/owner does and finally took it to the 'shop. Turned out to be the ECU. (That's the Electronic Control Unit.)

MikeIf it just stopped running without any prior indication of problems, most people will immediately point to a Hall Sensor failure. Might be true, might not. There are a couple of things you might try first though. Turn the ignition on and turn the handlebars right to left to the stops and back again. Does the fuel pump run continuously? If not check the wires around the control switch block. Check those wires anyway. Check all the wires around the head, a short in the wire from the tachometer where the wire crosses a frame member will cause this problem.On oil heads there are two Haul effects sensors mounded on a steel place the fits on the front of the engine behind the drive pulley for the alternator, check the pick-up wires. If you run the bike hard more often than not these do have a tendancy to melt, or at least get very brittle and crack letting moisture in. Also check the injector plugs on top of the control bodies, possible that there's a wire dislodged or broken there somewhere. At the extreme end, check the battery tray. Earlier models of the 850R had an acid battery, some without a breather pipe before that was sorted and if acid has spilled it would eat through the tray and compromise the wiring below. Like I said, an extreme possibility. Your other option is to find someone with a diagnostic tool or get it to a dealer, it may register and tell you where the fault lies.CheersGarry

Mike good to hear that your bike is going again. Looks like Garry missed the link in my post about the previous issues you had with the hall sensors.Back to that I will say from my own experience that the hall sensors can be replaced and your bike may go for 6 months but if the wirring from the hall sensors up to the plug has not been replaced then it is going to let you down again sooner or later mine went for about 6000kms without missing a beat and then stopped. This wire needs to be capable of withstanding temperatures up to 150 deg Cgood luck boGSer

Great lot of written deduction going on guys and in hindsight it was pointing to high resistance . The factor for me was that you were getting fuel a sign that the ignition signals were there.  Injection relies on ignition cofirmation but there was just not the power suffient to charge the coil even though signals were occuring.  Multimeters and a good inductive pickup timing light are great tools for THAT BLOODY TASK. Shiney side up Paul