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Discussion Starter · #1 ·
HI ALL, I HAVE A PROBLEM WITH MY F 650 GS 2001, WHEN IT BECOME HOT (FOR EXAMPLE IN OFF-ROAD) AND THE COOLING FAN TURNS ON THE IDLE IS OK BUT WHEN I ACCELERATE FROM IDLE IT GOES OFF AND IT LOOKS BAD FUEL

I TURN IT ON AND IT'S OK FOR A LITTLE TIME, THEN IT GOES OFF AGAIN AS SWALLOWED

I CLEANED THE THROTTLE BODY, REPLACED THE LAMBDA PROBE ,THE FUEL FILTER , THE SPARK AND CHECKED THE RESISTANCE OF THE IAT, IT SEEMS OK.
SOME ADVICE?
THANK YOU
(SORRY FOR ANY ERRORS I WRITE FROM ITALY WITH TRANSLATOR ...)
 

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Check the battery connections are clean and tight.
Check the voltage that the alternator is putting into the battery when the engine is idling and also when it is running.
When the fault appears and the fan is running, disconnect the fan and see if the fault stays. If the fault clears when the fan is disconnected then check the main earth cable on the battery, and the checks above for charging.
It could be a dirty electrical connection, and when the fan comes on the engine BMSC is not getting enough voltage to run properly
Pete
 

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Discussion Starter · #4 ·
hello, I did the tests and with the engine at idle the voltmeter shows 13.2v, when I accelerate it drops to 12.9 / 13v and if I accelerate a little it turns off, will it be the charge controller or the stator?
I tried to post a video but the forum does not accept any extension ...
thanks to those who want to help me
 

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The most likely problem will be the regulator/rectifier.
To find out unplug the 3 pin plug that goes to the regulator/rectifier and check the voltages between the pins on AC volts.
Check all combinations, the alternator is 3 phase so has three outputs, and so you need to check all three.
Check from the outside to outside pins, then outside to centre pin on both sides.
If the voltage is below about 20 volts when you rev the engine then the alternator is suspect.
If you get good readings on all three legs of the alternator output then try replacing the regulator/rectifier.
There are plenty of cheap ones on ebay, I have used an ebay regulator now for the last 5 years with no problems.
Another test you can do is to run the bike, then check the voltage at about 3000 revs. Then turn on the headlight and see what difference that makes. The regulator should send more power to the battery and the voltage should read around 13.5 to 14.2 depending on battery charge.
Oh and get your battery tested too.
You can do this yourself by testing the battery voltage with everything turned off. It should read above 12 volts to around 12.4 volts or more..

Then turn on the headlight and put the brake on, all without starting the engine and see how far the battery voltage falls. It should not drop too much.
Other than that take it to a battery shop and have it load tested.
Battery problems are deadly on those bikes
Pete
 

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Discussion Starter · #6 ·
Many thanks for the reply.
The bike has 80k km, the battery is new (yuasa), I only use it in off road, so it always works under stress, however tonight I will do the tests you suggested. I also noticed an oil leak on the central screw of the right crankcase (where the alternator is), perhaps the gasket broke and the alternator smeared with oil.
I keep you updated.
Thanks ag
 

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Discussion Starter · #7 ·
Hi I checked and the alternator measures 25v at idle and 50 / 60v when I accelerate, same in all pin combinations, so it's definitely the voltage regulator. I have already ordered it on Amazon .... as soon as it arrives I will let you know.
thanks again for your kindness and competence
Pier
 

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Discussion Starter · #9 ·
Hi, unfortunately the replacement of the rectifier did not solve the problem, now, when the engine is warms , if I open the throttle a little it goes out.
To start I have to overcome a vacuum between 2000 and 3000 rpm by opening the accelerator more than normal, but when it gets very hot it doesn't even hold the
idle. I checked the TPS and it seems to work, I changed the ignition coil, the spark plug .... I have no more resources ...
some other advice?
 

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Check and clean the Idle Air Valve. Also check that the clamps on the inlet manifold are tight and there are no air leaks in the manifold
Other than that see if you can find someone who has a GS911 to plug in and read fault codes.
Hope you find the problem soon
Pete
 

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Discussion Starter · #11 ·
Tonight I unplugged the tps as a test and, miracle, the bike no longer turns off when accelerating from idle, the idle is at 2000 rpm, I did a test ride and obviously it has gaps, but in any case it never turned off when restarting. ... I probably found the culprit ...
I seem to have understood that the tps is common to many bmw motorcycles and cars, because the original costs a lot ....
Thanks to those who want to help me.
 
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