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Do I recently bought a 2996 k 1200 rs with 30000 miles. Ran like a champ during my first 20 min test drive. Then at low idle sputtered a bit then would run fine. Took it out for a second test ride and the owner said it ran great for 30 but started to sputter at the very end of ride. I took it out 25 minutes after him. Ran great for a mile then started to act like it was low on gas. It wasn’t. It was hard to keep it from dying out on me and under power it would lerch forward then die down on idle. I’d pull in the clutch to get the rpms up and it would run rough and want to clunk out on me. Any thoughts? Fuel filter? O2 sensor? Spark plugs? All though it odd how well it ran until the 20 or so min mark. Got a great deal on it. Just need to get it going so I can take a trip in 5 days
 

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Jon96k1200rs,

I think I'd start by looking for a low charge on the battery. If you have an AGM type battery (Odyssey PC680, Westco, etc) sealed battery (Not a Lithium type), and the stock voltage regulator, the AGM is only getting 80% charged. If your plug-in maintenance charger is not AGM rated, same thing. AGM's need 14.5-7 volts to fully charge and the OEM voltage regulator does not go that high. When a battery sits with less than 100% charge the plates sulfate and the battery begins to fail. The BMW Motronic ECU really likes a 100% charged battery, too. Might be where you are. It happened to me, that's when I found out about AGM's, voltage regulators, chargers, etc. Bikes this age were designed for the old flooded plate battery (where you check the water in the battery and add when necessary) with a 13.5 volt regulator. AGM = Absorptive Glass Matt (between the lead plates).

Another symptom you have that says this might be a low battery is that it ran ok after sitting for a while. A low battery will slowly revive itself somewhat if left alone for a while, which it sounds like what you experienced.

IF you do have an AGM battery, get a charger like a BatteryMINDer model 2012-AGM (Amazon - $89). These have a desulfation cycle that will recondition sulfated cells. I didn't believe it until it fully revived my dead PC680 which is still going strong.

You can replace the voltage regulator in the Bosch alternator with an AGM rated regulator from EME for $39 : Voltage Regulators and Rectifiers (diode board) for a properly functioning charging system


Fuel - water in the fuel, fuel filter full, injectors plugged up, bad fuel pump. Put a dose of Techron concentrate in the tank. I do this every so often and it helps keep things clean. If that improves the situation, then keep looking at these fuel issues.
 

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That's interesting about the BatteryMINDer 2012 and AGM batteries. I had an Odyssey PC 680 that died at two years of age. Been using an older Battery Tender Plus. I bought the BatteryMINDer 2012, actually received it in two days free, and hooked it up to my 2 yr old Yuasa AGM, and it's been doing a lot of desulfating.

Thanks for the tip...
 
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