Rectifier and fuse.

Al, I think Nelson's bike has the later three phase generator and RR which means the drawings need to be for the RR53 which has no separate sensing line on it.
I refered to the brown wire above as that (according my 748/916 factory manual at least) splits after the fuse to feed the RR with clean battery voltage but also feeds the engine run and engine start relays switching coils. The one that goes from the engine run switch to the back of the bike is then used to switch the relay for the fuel pump and coils. My concern is that if the engine sensing connection is disconnected and sealed then the only current draw on the circuit should be the ignition relay switching coil (which should be minimal) or internal to the ecu, as I understand it the whole circuit is earthed through the ecu. This concern is heightened as the current goes up when the ecu is controlling the engine at higher speeds, I think this circuit should run at a stable low current all the time.

Ultimately the current in the circuit is dependant on its resistance, it should not be an issue with the theoretical output from the alternator system unless the resistance is high. That is why the connecting pins on the circuit need to be clean. I was hoping that there would be evidence of a high resistance contact in either of the two connectors or at the relay coil contacts.

A final thought was this, is the bike running a 1.6 or P8 ecu or something else set up for the 1098 engine? If the wiring loom is different from the normal 748/916 system (used for either type of standard ecu) then I may need to think again

Nelson, if you have difficulty in getting the relays quickly I have two spares (keep em in the Mars bar sized space next to the toolkit under the seat). Also I think you are 5 mins away from me.
Also you may want to have a look at the main ecu power supply plug under the seat. Make sure its clean and tight just to eliminate an earth issue through that plug (the black wire is the one to check).

 

I suppose I did oversimplify my hunch as i've not got out the circuit diagrams yet (and don't posses a 1098 version anyway) but until someone who can verify that the equivalent 1098 output should be the same (be it a necessary output or not) then I can't see the harm in sticking to this line of thought Nelson. I've recently been dealing with XR Honda field windings, uprated over the years resulting in fuse ratings that did increase for the later models.

 

Chris the fuse is rated as low as it needs to be to enable the circuit to work reliably. More importantly its rating is designed to protect the bike electrics from being damaged, usually by a failure downstream of the fuse causing an excessive amount of current to flow. It is not an issue with the power capabilities of the regulator output unless there is a fault condition - or perhaps a poorly designed circuit which is causing more current to flow than is necessary to work the various systems. Is the XR system a simple dynamo with a tichy battery by chance?

The current flowing is dependant on the power or "work" that occurs through the circuit and in this case the maximum "work" is limited to 36w of power by the fuse. The relationship between power, current and voltage (Power W=V x I) and Ohms law (V(voltage)=I(Current) x R(Resistance)) come into play.
The later 996/748s have a 520w system (with a 40A master fuse after the regulator) but the similar circuit on those bikes still retains that 3A fuse in it, the circuit essentially does the same thing. The only differences being the sensing connection to the regulator on the old system (hardly any current required) and on the later ones the load of the safety relay coil also run through that 3A fuse but the relay would contribute a negligible current requirement.

Nelsons current readings indicate that approx 30% more power was going through the fuse than intended and in reality it's running at probably 4 times the power than it should be. Put another way 30watts of power is being dissipated somewhere - possibly as heat - this is a quite a lot of heat and it gets worse, as heat builds up so does the resistance.


Nelson, you mentioned previously that the fuse blew at speed on the A419, but just stated that you witnessed 3.5A on start up. This would seem to indicate an intermittent problem, the most difficult ones to pin down unfortunately

FWIW I am starting to wonder if the fault is simply down to a poor earth contact from the ecu or a broken earth wire somewhere.

 

I respect what you are saying Steve but just applying pure logic :- 1/ The circuit has a fuse so one would think it's capable of a fluctuating supply. 2/ If you or anyone else can tell me that the equivalent 1098 alternator circuitry is the same as the 748 in this respect then I will have to take your word for it but it's a daft thing to assume without knowing this already or further investigation. The 3.5 amps that Nelson is experiencing seems to be a pretty stable peak and I still thinks it's a possible characteristic of 'the conversion' rather than a fault that needs finding. Meanwhile of course it's worth going through every connector and earth as usual looking for resistance/light corrosion but i'm pretty sure Nelson is aware of this now

 

Chris you may be right but that 3.5A is going through places it shouldn't be. I wonder if anyone else on here has this set up?

Also the fuse is there to limit damage if a fault occurs (say a relay shorting out due to water ingress) and I honestly believe this circuit should be running at a pretty fixed current. As the regulator is the key component supplying the battery and everything else and the regulator is common between the later 748 and 1098 (assuming the electrex site is correct) then I don't agree the difference can be that great. There is no real difference in the circuits in question and a 520w regulator can supply 520w, but only when 520 watts is demanded by the load.

Interesting problem I have to say

 

Nelson mentioned that the peak appeared to be ~3.5A on start up, but <1A on tickover. I wonder if the 3.5 he saw was only a momentary peak value and not of any significance.
Interesting to know what instrument was used to get these values!

 

xxy

 

John that is a good point as the momentary current increase could simply be the current required by the starter solenoid switching coil. As this is a 1098 engine it may have a different solenoid from the normal 748 one.

Sorry for the duplicate post, having trouble with the system freezing. Bluddy Microsoft

 

Did you ever get any more understanding of what was happening here Gary? @Nelson - @TNR is searching for something similar and so I was reading through old threads that might shed some light.