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Electrical issue and fault finding chart.

Discussion in 'Technical and Troubleshooting Torque' started by Zealous, Dec 30, 2012.

  1. #1 Zealous, Dec 30, 2012
    Last edited: Dec 30, 2012

    When performing the rising vaults test (1st steps in the chart) it says increase the revs to 2500rpm and it should read above 13.5, which mine does. But when I rev to 5000 is shows up as 13.48v, I'm curious is this normal? The reason I ask is because I traveled to Bondi Beach the other day and my bike was acting up, turned out to be the fuel pump not effectively pumping the fuel to carburetors so I installed some clear line to view the fuel behaviour and indeed the pump isn't strong enough to pull the fuel past the inline filter, nor is it strong enough to push the fuel all the way to the carburetors. The suction from the carburetors is helping the pump get the fuel in so I disassembled the pump and all looked fine inside, I'm no expert on fuel pumps but the gasket seemed in good condition and the mechanism responsible for pumping the fuel seemed to operate as it should.

    Anyway this morning I noticed the starter relay was struggling indicating a flat battery. I placed the battery on charge for a few hours and the bike seems to be running good. Problem is I get 2 weeks of commuting before the battery needs a charge. Also when I test voltage on the connection which travels to the fuel pump I'm getting a reading of 10.96v, which means that's what the pump is getting, is this right? Shouldn't the pump be getting 12v and not 11v? I checked a few other things like indicators, coils and thermo switch and the connections are showing 10.96-11v?

    I removed the stator cover and inspected the alternator, all seems fine. Furthermore his is a new reg/rec.

    Can a bad negative connection somewhere on the bike cause this? I'm thinking the problem is in the harness somewhere but how do I isolate it?

    Would greatly appreciate some ideas.


    - Zealous
    • Like Like x 1
  2. Electrics sound OK to me from what you have stated. The carby's do not suck fuel they just control the flow to keep the float chamber at the correct level. They used to be just gravity fed but I guess these days that doesn't supply enough fuel at high throttle so they are aided by the pump. Sitting there revving the engine under no load will not use a lot of fuel so little will be seen to flow. The voltages you stated are expected when power is drawn. Similar to the fuel, draw small current and the voltage at both ends of the wire will be the same (almost), draw higher current and the voltage at the end of the line will drop. Your alternator and regulator are fine by those readings as they are putting out the required charge and holding it constant when you rev it. .02 of a volt is irrelevant, probably outside of the meters accuracy specs. If you commute only short distances then the alternator will not have time to replace the charge used to start the bike and the battery will slowly go flat over time. I would get the battery tested before I tore into the electrics or the fuel system.
  3. Have you changed the battery?
  4. #4 Zealous, Dec 30, 2012
    Last edited: Dec 30, 2012
    Yes, this is a relatively new Motobatt battery. No more than 4 months old and hasn't seen a lot of use until now. I just charged the battery and put it back in. I rechecked the fuel pump connection and it is reading as 12.09v.

    I'm glad things seem OK regarding the electrical system. I do commute only short distances and most is idling at lights so you're probably right regarding the alternator not having enough time to recharge.

    The reason I mentioned carburetors sucking is because I noticed the fuel level in the hose was just below the fuel intake for the carburetors and it was suddenly drawn in but I didn't hear the pump.

    What was happening when traveling to Bondi was definitely fuel starvation. It was as if there was a blockage in the fuel line causing the carburetors to starve and as a result the bike would jerk, and throttle response was erratic which could have been disastrous on the M4.

    I had a rev hanging issue for some time but its not as bad as it was previously. Turned out that it was running lean so I adjusted out the fuel/air mixture screws and it helped. Also I recently increased the idle jet from 12.5 to 15 and it definitely idles and runs better but I still get a slight hang above 2000, when it should be 1600. When this happens, say for example when coming to a stop at a set of lights, I can put some pressure on the throttle (Clockwise) and the hanging drops. The cable does have a kink in it but it snaps back as it should. I'm thinking it's one or two of the four throttle butterflies not reseating as they should after being opened. I balanced the carburetors 3 or 4 times now but maybe its a bad adjust spring or perhaps something is sticking; whatever it is its very minute.

    What do you mean by get my battery tested?
  5. I am not knowledgeable on Mechanics so can't help much. My field has been electrical and electronics. Being a relatively new battery I doubt it will be at fault. A failing battery can take a charge and show full voltage immediately after but when put under load its voltage can drop significantly. Off load a fully charged battery should show around 13volts at the battery terminals. switch on your ignition and lights but do not start the engine. The voltage should not drop more than 0.5 volt or so. These figures are not absolute as the accuracy of your meter has a bearing. If in doubt then any decent battery supplier (eg Battery World) or auto electrician should be able to test it simply for you and they usually don't charge as if it is faulty they get a sale.
    • Like Like x 1
  6. The battery reads 12.80v at terminals, switch on ignition without engine running and it shows as 12.40. That's a difference of 0.4v. So nothing to worry about then?
  7. I don't see any problems there. If your battery keeps going flat then it needs a good run to get it charged or there is some circuit not being switched off when you park the bike and is draining the battery. Idling at lights and short distances will drain a battery and shorten its life but I would expect a few years before it dies not a few months. Get out on weekends and that will help keep it charged.
  8. Will do, thanks!
  9. Zealous, your twin headlight conversion may have bumped up the wattage/amperage of the headlamp, such that the starter motor is struggling a bit.

    My Zeal's rectifier/ regulator reads much the same as yours and I would have liked it to read say 14- 14.5 volts limit when I revved it over, say, 3000RPM.

    At present, after buying a new battery last month, I still feel the battery is not charging enough to account for the drain on by having my hard-wired head-lamp. For this reason, I am fitting an on/off switch in the red/yellow wire to the head-lamp 15 amp fuse, to allow easy starting. My trouble is where to have a neat fitting.... I'm thinking of near the choke pull/push.

    RegardZ .
    PS. my light is supper bright. I have not checked the wattage yet, however the previous owner definitely wanted a powerful light.
  10. A few minor points that might be pointless,
    Unless its zeal specific I thought most bikes' battery charging/generator systems aimed to pump out ~14 to 14.5V above 5000rpm? The idea above about the impact of the additional headlight might be worth looking into and would be quick to check.

    and it might have been a typo, but you mentioned your charging system provides
    more than 13.5 volts at 2.5K and 13.48 at 5K, that doesnt sound right. Did you do the other tests on that sheet despite being marginally over their threshold? Particularly the ones regarding battery connections, leads, and connecting the RR all the way through to the RR? Aftermarket RR's and wiring kits from roadstercycle recommend bypassing the original harness connections straight to the battery (worked for me 13.7->14.4).

    From http://roadstercycle.com/Shindengen FH012AA Regulator upgrade kit.htm
    "I get a lot of calls and Emails about using your old harness that goes from the old R/R to the battery. My answer is don't use it! just unplug it and tape the end off so it can't touch any type of ground and ty rap somewhere safe. It will still get power from the battery side if there are other systems that use it in the bike. Use the new 10 gauge wire I send you to go from the new Mosfet regulator to the battery, put in a maxifuse the equivalent size of the one that was originally in your bike. The problem is that if you use your old harness any issues that are in that old harness, like bad connections, bad solder joints, bad grounds, etc will just defeat the purpose of upgrading your charging system. Lets do this clean with all new connections crimped and soldered and you will have a bullet proof charging system."
  11. I agree Zealous float charge for a battery is 14v upwards. You are not getting into a clear charge level voltage for the battery.
  12. are the battery terminals clean , when new battery was installed were the fittings polished up
    ' sandpaper .
    i say this because charging is a low draw
    starting is a high power draw so yih can have a battery starting but not charging ' hsppens a fair bit .