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Discussion Starter · #1 ·
I went to start my 98 F650 after sitting since October, the bike eventually started after a lot of winding and connecting the charger. The bike would idle fine but would not rev, I discovered that if I switched it off and left it for a few seconds the bike would start and Rev ok then die to idle again. Thinking it was a fuel issue I checked the fuel tap which was letting the fuel through fine. I then removed the carbs, cleaned them and checked the fuel jets etc....apart from a few small drops of water everything was good. I then reassembled everything and to my disappointment the bike was just the same.!! Now for the interesting bit.....whilst the bike was idling I inadvertently clipped the heated grips switch, this had the strange effect of changing the revs, I noticed that the lights were off (I’d switched them off when trying to start the bike earlier) as soon as I put the headlight on the bike would rev and drive perfectly!!
Has anyone come across this before or have any suggestions as to the problem??
 

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Discussion Starter · #2 ·
I went to start my 98 F650 after sitting since October, the bike eventually started after a lot of winding and connecting the charger. The bike would idle fine but would not rev, I discovered that if I switched it off and left it for a few seconds the bike would start and Rev ok then die to idle again. Thinking it was a fuel issue I checked the fuel tap which was letting the fuel through fine. I then removed the carbs, cleaned them and checked the fuel jets etc....apart from a few small drops of water everything was good. I then reassembled everything and to my disappointment the bike was just the same.!! Now for the interesting bit.....whilst the bike was idling I inadvertently clipped the heated grips switch, this had the strange effect of changing the revs, I noticed that the lights were off (I’d switched them off when trying to start the bike earlier) as soon as I put the headlight on the bike would rev and drive perfectly!!
Has anyone come across this before or have any suggestions as to the problem??
UPDATE
I put my voltmeter across the battery and started the engine?...over 17V at idle!! So I had a look at the voltage rectifier and found this on removal!!

7DDF017F-147F-442A-9BBD-31A5DA7A9362.jpeg
 

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The rectifyer / voltage controller has got a very limited lifespan. The problem is caused by its location under the seat. It cannot dissipate the heat it generates. If you move the unit away from under the seat (on mine I extended the wires and bolted it under the right side (outside) under the seat. If you wish, I can send photos. Godd luck from the north of Germany,
Horst
 

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Discussion Starter · #4 ·
The rectifyer / voltage controller has got a very limited lifespan. The problem is caused by its location under the seat. It cannot dissipate the heat it generates. If you move the unit away from under the seat (on mine I extended the wires and bolted it under the right side (outside) under the seat. If you wish, I can send photos. Godd luck from the north of Germany,
Horst
Thanks for your quick reply, Relocating is a good idea. What type and where did you get yours from?
 

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Discussion Starter · #7 ·
Thanks everyone for their contributions, I have managed to get hold of a Pegaso rectifier.
 

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The rectifyer / voltage controller has got a very limited lifespan. The problem is caused by its location under the seat. It cannot dissipate the heat it generates. If you move the unit away from under the seat (on mine I extended the wires and bolted it under the right side (outside) under the seat. If you wish, I can send photos. Godd luck from the north of Germany,
Horst
As Horst says sounds like it's the VR, should cut off about 14.6V, after market (non BMW & cheaper!) VR widely available, best relocated for Cooling as said. Plenty of details in FAQ's . Battery will fail eventually if not rectified.
 
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