B4 750 voltage fluctuations - MVAgusta.net
 
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post #1 of 7 (permalink) Old 09-10-2016, 05:33 AM Thread Starter
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B4 750 voltage fluctuations

Hi guy's. I am still fiddling around with the hesitation jerkyness 1000-3000 rpm problem. There were no improvements after I temporary fitting a new tps and air pressure sensor. Recenly i had a few main beam fuses popping for no apparent reason, i have reconnected all connectors, found nothing but fuses stopped popping.

Question: Today i was probing around with a multimeter and noticed voltage changes. The tps sensor voltage was switching up and down 0.5V when i actived the indicator lights or switched between high and main beam. This voltage change was also noticable when probed over the battery. It occurres with engine off and running. I never experience starting, stalling or charging problems and the voltage stays stable when the bike is left untouched. When i rev the engine the lights do become brighter. What could cause this behaviour?

I suspected something to be interfering with the tps or injector signal that causes the system to inject a short burst of fuel into the engine with the slightest throttle movement what causes a jerk.
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post #2 of 7 (permalink) Old 09-10-2016, 06:23 AM
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Could be a few things so a few questions.
Do you reset the TPS as per instructions ?
How old is your battery?
I assume you have decent connections or battery and fuses ?
What's the voltage measured on battery with bike running, testing as per manual instructions ?
Have you balanced throttle bodies and checked for air leaks ?

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post #3 of 7 (permalink) Old 09-10-2016, 06:50 AM
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My first thought was to check the battery connections and the ground at the ecu mount.
However you say the voltage fluctuates across the battery when switched off so maybe you are losing a cell...

The light increasing when you rev indicates the alternator is charging....Check that charge voltage across the battery..Should be 14.4 volts area.
If more this could be why your battery is screwed.


Joe

Last edited by gotojoe; 09-10-2016 at 06:53 AM.
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post #4 of 7 (permalink) Old 09-10-2016, 07:07 AM Thread Starter
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Quote:
Originally Posted by Donsy View Post
Could be a few things so a few questions.
Do you reset the TPS as per instructions ?
How old is your battery?
I assume you have decent connections or battery and fuses ?
What's the voltage measured on battery with bike running, testing as per manual instructions ?
Have you balanced throttle bodies and checked for air leaks ?
I did not reset the tps. I installed the borrowed and reinstalled my onw tps at the setting i took it off (~325mV)
The tb's were balanced a short while back. (Were in decent range.No change in hesitation after balancing). The vacuum line caps were in bad condition and have been replaced)
The connections on the battery and fuses are in good condition.
I can't find a manufacturered date or code on the battery (yuasa yt12a-bs).
It reads 12.7volt turned off and 13.7 - 14volt idling. And 15ish at 2000rpm. (i just noticed that it is difficult to balance the engine between 1900 and 2800 rpm. It kinda gently jumps from 1900 to just below 3000)
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post #5 of 7 (permalink) Old 09-10-2016, 09:12 AM
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You need to reset the TPS, you have the adjustable one on the 750 right? Even if you have the solid mount, you still have to set it properly.
How does your ECU know if your throttle is closed or open and at which angle if you don't tell it first. That's what TPS is all about mate.

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post #6 of 7 (permalink) Old 09-10-2016, 12:40 PM Thread Starter
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Quote:
Originally Posted by Donsy View Post
You need to reset the TPS, you have the adjustable one on the 750 right? Even if you have the solid mount, you still have to set it properly.
How does your ECU know if your throttle is closed or open and at which angle if you don't tell it first. That's what TPS is all about mate.
Well I'll get that sorted a.s.a.p. just to be sure.

But why would it matter? The bike was running fine at first, then the jerky throttle started for no apparent reason, then i tried a different tps which i calibrated to the same mV als the one i took off the engine (which made no difference) then i mounted my own tps again which i calibrated to the same voltage as it was set when i took it off. So theoretically everything is back to where it was so the ecu knows at what angle the tvalves are. I think the engine would barely run if i hadn't set it to the same voltage as what it was when i took it off.

*Edit.Sept11: Just got the tps reset. Still jerking. Tps was off a bit (closed throttle tps signal was ~200 mV instead of 150mV), and the throttle cable was slightly overtensioned. The bike now idles and runs better but the jerking is still the same.

Besides that. Is the dip in voltage caused by switching on lights acceptable or unusual? Or the brighness going up slightly when revving is that normal?


Quote:
Originally Posted by gotojoe View Post
My first thought was to check the battery connections and the ground at the ecu mount.
However you say the voltage fluctuates across the battery when switched off so maybe you are losing a cell...

The light increasing when you rev indicates the alternator is charging....Check that charge voltage across the battery..Should be 14.4 volts area.
If more this could be why your battery is screwed.


Joe
The charging voltage is around 15volt, which is not that much more. Does that indicate that the battery dying?

I will check the ecu mount ground to be sure.

Last edited by Robbedoes; 09-11-2016 at 08:32 AM.
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post #7 of 7 (permalink) Old 09-10-2016, 01:09 PM
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The lights brightening and dimming is normal for reaction to the voltage regulator circuit doing its thing.
Charging voltage of 15 VDC is ok, but much higher than that and you'll start overcharging your battery.
Overcharging your battery will cause things like warped plates and electrolyte boiling.

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