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1993 750 Electrical gremlins

Discussion in 'RC36' started by KGVFR750, Aug 30, 2017.

  1. KGVFR750

    KGVFR750 Registered User

    So I got my new chain and sprockets finished and I went to start the bike (been sat trickle charging for 3 months) and not a thing happened, the ignition lights take a while to come on and when I press the start button the dim really low (which was making me think its the starter jammed or an earth or something). So I've checked the battery and its got 13v I've looked at the starter relay (not tested as I don't have spare wire etc) and I'm getting 12v at the B terminal (straight off the battery) I'm getting 12v at the fuse and I'm also getting 12v going to the Red/White wire (Rectifier) and going to the Red wire (ignition switch and clock). my question is do I need a 12v signal from the clutch diode and the starter switch for the starter relay to activate and then send 12v to the starter? or could I supply the M terminal of the starter relay a 12v supply straight from the battery to check that its actually turning the engine?

    With ignition on and in neutral I'm not hearing any click from this starter relay at all.

    Thanks folks
     
  2. KGVFR750

    KGVFR750 Registered User

    so I've just went and tested the Starter Relay Switch by supplying the Green/Red terminal and the Yellow/Red terminal with 12v and it clicks no problem and I get continuity from B post to M post. so I have something else the problem, its not clicking when its fitted so must be a problem with the starter button supply or the Clutch Diode supply
     
  3. KGVFR750

    KGVFR750 Registered User

    so I cleaned a few grounds and disconnected the M post on the starter relay switch and the ignition lights came on no problem and the relay clicks every press of the starter button along with continuity but still no start when I reconnected the M post only few clicks of the relay. I removed the starter and checked it too and it rotates freely. Going to give the battery a good charge over night then if its not working ill buy a new one
     
  4. JZH

    JZH VFR Club Bodger

    How old is this battery, exactly? 13v is so good it's slightly unbelievable! Methinks maybe you're reading the surface charge? 13v is higher than I would expect any used battery to read. Do you have another battery you can try?

    Ciao,
     
  5. KGVFR750

    KGVFR750 Registered User

    age of the battery could be anyone's guess, its not even the right part number its a YTX12-BS and not the HTX12-BS so today I bought a cheap battery (until the HTX12-BS gets delivered to my local Honda then return the cheap battery) just to start it up and got it going but kept on cutting out and cut out when the head light was switched on, so I dug deep into the loom and found horrible wire repairs in the main loom that have been soldered and insulate tapped etc, so going to sort them out tomorrow
     
  6. JZH

    JZH VFR Club Bodger

    Good luck! VFR electrical gremlins are the pits, but you have to start somewhere, and that's usually with a known, good battery. Repairs to the main wiring loom suggest that the bike has suffered the usual electrical problems in the past, and they may not have been solved properly at that time.

    Btw, the battery number depends a lot on the manufacturer's whim. The OEM battery would have been a Honda-branded Yuasa, so the Yuasa battery numbers are considered the "standard". Yuasa numbers usually start YTX, but others will start GTX or (I guess) HTX. What matters is the physical size, the capacity in Ah and the orientation of the battery posts. After that, it's just a question of manufacturing quality. I tend to stick to the major brands, currently using the yellow ones in most of my bikes...MotoBatt. The OEM size was essentially YTX12-BS, though you could probably fit a 14, which is just a little taller.

    Ciao,
     
  7. Pete Cas

    Pete Cas Well-Known Member Club Sponsor

    Yes, as you say JZH, the original 'standard' battery was a YTX12-BS. I've not used any different ones since I've had my FL (and that's from new), and not had any problems with Yuasa ones, other than old age.
    KGVFR750 - has the battery really been on trickle charge for three months? That won't have done it a lot of good! Or do you mean it was connected to a battery tender?
     
  8. KGVFR750

    KGVFR750 Registered User

    thanks for the replies guys,
    so YTX12-BS is the actual battery!!??!! uugghh I could have bought one two days ago ffs! Honda parts man said its an HTX12-BS and I'm not getting it until tomorrow. I'm actually depressed as I could have been out today as it was so nice today
     
  9. KGVFR750

    KGVFR750 Registered User

    Pete Cas, its been on trickle for three months and all over winter, I was told it'll stop it from draining over winter and the trickle charger boasts a shut off so it doesn't constantly charge it. so I think you're right with the trickle charger has probably knackered it and I wont be doing that with the new battery
     
  10. KGVFR750

    KGVFR750 Registered User

    Well I just nipped out for a 100 mile faultless run! feels good to get back on the bike. Every time I have a problem I feel like selling it or burning it but when I fix it and get back on it brings a massive smile to my face. What a difference a new chain and sprockets make!
     
  11. KGVFR750

    KGVFR750 Registered User

    JZH,

    I just went out on a run as I had problems again, I just checked the charging voltage at 5000 rpm with the head light on and was getting 13v, ive checked the manual and it states 13.5v-16v but doesn't mention the head light? now I think if I had the head light off I might have gotten up to or better than 13.5v? cant check now as its tool late. do you think there's a problem?
     
  12. oldburnthippy

    oldburnthippy Registered User

    Buy a cheap and cheerful ammeter from eVilBay. Tells you what your battery is gonna do before it does it - shorts, overloads etc.

    Where are you measuring the 13V?

    Wiring - been there; why would anyone cut into a HIDDEN bit of harness, insert the odd extra four inches of black cable, then twist and tape it for the next poor bugger - me - to find? Five examples so far:mad:
     
  13. lee j

    lee j Registered User

    That voltage reading of 13v is on the low side (are you measuring across the battery terminals to check the voltage produced from the reg/rec?)- would have expected 13.5-14v being produced, even on a new battery, especially with headlight on as to replace what is being taken from the battery into the circuit and by starter. 16v charge is very much on the high side - as anything over 15v is considered high and can damage a battery.
     
    KGVFR750 likes this.
  14. lee j

    lee j Registered User

    Sounds like someone has had an alarm fitted and then removed using an in-fill cable to original circuit. Though a bit stupid to twist and tape joints.
     
  15. KGVFR750

    KGVFR750 Registered User

    Thanks Lee j, that is across the battery terminals and the battery was 12.8v after my run. is this pointing to a reg/rec? could doing the resistance tests on the rec confirm its that?
     
  16. lee j

    lee j Registered User

    Before saying - yes it is the reg/rec you will need to check the alternator output to make sure that it is producing the correct amps across the 3 phases and also not shorting to earth. If the alternator AC current is down on a phase then the reg/rec will not be able to produce the correct DC output.
    Have a look at the thread titled - Battery Question by Newfish as he has similar problems and have also replied to him regarding various items to check including alternator output etc. You will also have to check the battery is holding charge and not dropping low when starting as this could indicate a problem battery (even new ones have been known to be problematic/faulty)
     
    Last edited: Sep 7, 2017
  17. KGVFR750

    KGVFR750 Registered User

    It looks like I may have found the gremlin! right, I started again from scratch! battery before testing 12.8v - book says 12.8v so that's good
    First up was a leak test and its 0.80mA the book says 1.2mA MAX so that's correct
    Next charge voltage. warmed up the bike and it was 13.2v @ 5000rpm headlight off - book says 13.5 so that's suspect
    next was rec harness. Checked battery voltage 12.8v, rec harness Red/White(+) and Ground(-) should be battery voltage and it was 12.8v so that's correct
    Green and Ground = continuity and that's correct
    Next Charging Coil, yellow and yellow (there was 3 yellows? so I tested all) got 0.6ohms book says 1.0-2.0 @ 20 degrees C. Suspect there??
    Next I pulled the reg/rec and tested that for resistance:
    (-)on pin 2 to (+)on pin 1 book says 0.5-10 kohms I was getting 0
    (-)on pin 3 to (+)on pin 1 book says 0.5-10 kohms I was getting 0
    (-)on pin 4 to (+)on pin 1 book says 0.5-10 kohms I was getting 0
    (-)on pin 5 to (+)on pin 1 book says 0.5-10 kohms I was getting 0
    and I got 0 for the remaining resistance tests and after 10 minutes of running the bike to warm it up the reg/rec was so hot I couldn't touch it
     
  18. KGVFR750

    KGVFR750 Registered User

    So I just checked the alternator output at the 3p connector and I got 0.6 ohms and it should be between 0.1-1.0 ohms so that's good
     
  19. KGVFR750

    KGVFR750 Registered User

    Ill do it started tomorrow, end up annoying the neighbours doing it now haha but I have a question Lee J: when testing the Rec harness at the plug it says the yellows should be 1.0-2.0 ohms but at the 3p plug after the alternator it says the yellows should be 0.1-1.0 ohms, why is that? its the same wiring from the alternator right to the Rec?
     
  20. oldburnthippy

    oldburnthippy Registered User

    Hadn't thought of an alarm - never had or needed one.
    It would explain the cut wires to starter relay, fuel pump and ignition LT.

    AMONGST OTHERS
     

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