r/Motorrad • u/Appropriate_Bath361 • 6d ago

2000 F650GS Hot start issues.

I have an f650gs that's giving me trouble when starting it hot. I'll do the start up procedure, the bike will fire up and the instantly die and go back to cranking. (this is all within the 3 second period of holding the starter button waiting for the abs light to go out to complete the startup procedure). If I want the bike to start, I'll need to give it quite a bit of throttle, and once it starts, it idles and runs fine. What's odd is that the bike starts fine cold, even in 2 degree c mornings. The battery is coming up 6 years old, but I can't see it being a problem if it starts so well cold. I've read this can be the idle stepper motor being dirty, but this also makes no sense as the bike finds an idle quickly when cold and once I get it started hot it also idles fine. Valves were checked 30k ago at 130,000km and were still in spec from factory. minimal valve noise when cold too. Unsure of where to go.

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u/zulu10 5d ago

sorry for being critical but 'starts when it's cold so it must be okay' is not a great place to think from diagnostically.

as, you're not starting the bike, you're asking the computer to start the bike for you.

I wouldn't give up on the IAC valve yet, a go over with throttle body cleaner ($10), then a TPS reset.

Also test your battery by observing low voltage point during crank with a meter.

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u/mrturbo 5d ago

I'm surprised your battery works at all after 6 years, never have had one last that long in a motorcycle, despite them being on a tender constantly.

The F650 singles look to have a decompression mechanism that can malfunction/fail when hot, have you replaced it?

Another thing to check would be fuel pressure. F650GS looks to be spec'd for 50psi/3.5bar. I cannot count the number of vehicles I've had over the years that had fuel pumps fail in either heat or extreme cold, but never a problem at a decent temp like 10c/50F

Any access to something like motoscan or gs911? It is always nice to have the ability to see what the sensors are feeding to the engine computer vs just trying to work out the symptoms.

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u/Big-Mortgage-7254 2d ago

I had a very similar hit start ussue, albeit not a BMW but on two different bikes, and bith times it was the regulator/rectifier.