bike shuts off when fan comes on????

shorn87

Registered
2000 busa , the bke runs great until it gets up to temp and the fan comes on and then it will kind of studder and die. sent the injectors and had cleaned and tested, changed fuel filter inside pump, plugs where a little dark, bead blasted them. (previous test done while idling)
while riding the bike , may go 50 miles and doesn't happen or may not be able to go 15 miles without it dying 3-4 times.
 
Sounds like the fan is drawing too much current maybe? May be time to replace the reg? Im sure others will chime in with ideas.
 
Hey: Welcome!

:welcome:

As he said above may be happening, and I would try and turn up your idle to 1200 or 1300 (I keep mine at 1400) and see if that helps it.
What is the temp gauge doing when it happens?
 
Sounds like you have a short in the fan. Is it running when the temp goes up or perhaps the blades are bent.
 
Try and repeat the symptoms. Eliminate things first be removing the fuse for the fan and see if it will exibit the same symptoms. My guess is that you're not getting a FI light.
What other mods have you done to the bike?
 
Does it happen when the bike gets warm in general, or exactly when the fan kicks in?

What happens if you start the bike and leave it idling. In a few min it will get to the temp and the fan will kick in. Does it die then?
 
mods-
yosh exh
pc 2
yes it does it at idle, thats how i'm testing it.
everything in the gauges works as theyare supposed to
checked the charging system and seems to be fine, voltage at battery
it acts as if when the fan comes on, it triggers something, yet fuel pump continues to run.

what i have done to this point--
cleaned tank -- had injectors tested and cleaned-- new fuel line and filter
 
The fan blades arent melted where it wont spin are they?
as said before sounds like a current draw problem :dunno:
 
If the fan comes on, and the bike dies right away, it's clearly electrical. Take a voltmeter, connect to the battery and start the bike. Observe the voltage - should be somewhere in the range 13.5 - 14.5. Look what happens to the voltage when the fan kicks in. It should not drop more than 0.5V. If it drops more than that (and I am guessing such a drop causes the bike to shut off), then you either got a short somewhere in the fan circuit, or something is not right with your charging system/voltage regulator.
 
Look carefully at wire harness - wire chafing - maybe shorting the electrical system when it comes on... I haven't got a clue how a short in the fan would be immediately effecting electrical distribution if the battery is good? All signs point to voltage regulator, they're cheap and probably a good part to elimate... If it were the alternator the battery wouldn't be charging. Coil would be an on going problem. Maybe fan shorting causing a fuel pump voltage drop causing the problem but again if the battery is good I don't think that would be it...

Voltage regulator - Yeah that's it...

I'd wait around for a day or two - someone has had to of had this exact problem... and solution.

Voltage regulator...
 
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could be a combo problem of fan and fuel. Earlier Busa's were known for the fuel line to be pinched, couple that with a fan drawing to much power, taking away from the fuel pump and voila, you have a stall.
 
If the battery voltage drops below 12.5 volts the injectors will not fire, and the engine will die.
You may have a borderline battery, and the extra draw causes the voltage to drop.
Something still sounds irregular with the fan, like a short or burnt winding or something to cause the voltage drop.
Here is the battery test:

Batt Voltage.jpg
 
If the battery voltage drops below 12.5 volts the injectors will not fire, and the engine will die.
You may have a borderline battery, and the extra draw causes the voltage to drop.
Something still sounds irregular with the fan, like a short or burnt winding or something to cause the voltage drop.
Here is the battery test:

Oh.. I wouldn't trust that manual. A fully charged battery is 12.6V, and as soon as the key is ON it goes down to 12.0V, and when the starter cranks it's under 10V and injectors fire just fine. And I bet that most batteries on real bikes are not fully charged having less than 12.5V and their bikes start just fine. I measured all of this with a digitally calibrated V-meter permanently connected to my battery.
 
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