Welcome to Netrider ... Connecting Riders!

Interested in talking motorbikes with a terrific community of riders?
Signup (it's quick and free) to join the discussions and access the full suite of tools and information that Netrider has to offer.

Oh Uh, don't tell me it's the Alternator :(

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Zealous, May 14, 2009.

  1. There's a problem.

    I have a 1992 Yamaha FZX250 Zeal which has been stationary for some time (about 4 months). Recently purchased a new battery and plugged it in. Initially It took awhile for the bike to start (when it started there was a lot of black carbon coming from the mufflers etc.). Now each time I start the bike it takes ages to start (usually have to leave it in the sun for hours and recharge the battery - this is because the battery is going flat each time it starts.

    Oh man, an alternator will cost me a fortune brand new (hundreds), and the wreckers, well, I'd need a hell of a lot luck finding one for a Zeal from the wreckers.

    I am currently checking the wiring to ensure nothing is disconnected. I've replaced the spark plugs and just this morning replaced the oil, oil filter and cleaned the air filter.

    - Choke works fine (yes, I have tried the choke in many positions in hope that it starts)... bike only seems to start when the battery is fully charged. Once warmed up, it starts each time but I'll leave it over night, try start it in the morning and it doesn't start (even with choke fully out). Continually attempts to starts but I just stop because it will end up killing the coils or battery.


    I need a multimeter btw, I don't have one but may be able to borrow one off of my neighbour... I don't know what I'm doing to test the alternator with a multimeter therefore instructions will be greatly appreciated.
  2. Quick check for a buggered charging system is a rising volts test.

    Get a baseline by measuring the voltage across the battery terminals with the bike off.

    Then start the bike and warm it up until it will idle normally with the choke off. Idle should be to manufacturers' spec but if you don't have these, about 1000 rpm should be close for most engines.

    Connect the voltmeter across the battery terminals and check the reading. Then, with the meter still connected, gradually increase the revs while watching the reading. As the engine exceeds a fast idle, you should see a distinct rise in the voltage reading.

    If you don't get a rise, it's likely that your charging system is not as it should be. Most likely the rectifier-regulator rather than the alternator, but the rec-reg can take the alt with it if it's not attended to promptly.
  3. is it cranking and not starting or its got no juice at all in the morning?
    you seem to indicate it cranks but doesn't fire unless warmed up??

    if its got no juice, i'm betting its the stator/generator (...see how i'm not telling you its an alternator :p ).

    you need to check all phases coming out of it with a meter.
    my bike has 3 wires coming out (call them AB&C) so i tested the voltage between AB, BC, CA and they were supposed to all be 65v+ at 5krpm but i got about 55v, 8v, 4v. sent off for rewinding ($250) and its all good now.

    my bike failed the rising volts test (hardly cracked 12v when revving it when it should get up around 13-14v) and my reg/rec tested within specs.
  4. If I recharge the battery tonight, put it in the bike tomorrow, it will fire but will not start (similar to when there's no fuel in the tank). To start it, I will need to sit it in the sun for a while, then start it. However, the battery seems to loose power due to attempting to start it so many times so I am forced to recharge it.

    When the bike is idling, it seems fine. Unfortunately, I haven't had the chance to take it for a ride yet so I can't really provide anymore information.

    Maybe it's just really bad fuel. It's been in the tank for months. I'll change it and get back to you.
  5. I dont know if this is the case but my partner and I bought a brand of battery dynovolt and they were both shit from new.They were exchanged for a yuasa and no problems.
  6. Mate of mine had a similar problem with his Suzuki GS250 Bandit.

    The only way he could get it going was a bump start. Found out it was the alternator. Battery was over charging so a 2nd hand alternator was fitted to the bike with a brand new battery... That lasted about a month. Then it killed the battery and died doing it.

    He ended up taking his bike to a dealer to get it repaired, they fitted a brand new (Honda) alternator and a new battery. Also cleaned the carb out.

    Cost him $650 with parts and labour.
  7. I would definitely put fresh fuel in it before doing anything drastic. Some bikes seem to be more sensitive than others, but it certainly won't be helping matters.
  8. You mention checking the wiring "to ensure nothing is disconnected", but you need to check better than that. Maybe sitting the bike in the sun dries out a connection, or expands some metal enough to improve a connection. Low voltage across the starter can result in the symptoms you are seeing, because the engine isn't being turned over fast enough to start.

    Read the "Starter Circuit" section of my post here: https://netrider.net.au/forums/viewtopic.php?p=997997&highlight=battery#997997 It's not specifically your problem, but note what you should check.

    Also, as mentioned above, sometimes new batteries can still be bad batteries. Constantly running it flat and recharging wont help either.

    BTW a properly functioning charging system should be putting out something like 14.2 to 14.7 volts, which is what you should read across the battery terminals while the bike is running. Check the specs for the bike if you can.
  9. Ok, update.

    I've got my hands on a voltmeter... also changed the fuel, oil, spark plugs, oil filter, coolant, fuses and bulbs. Checked the wiring as well as the connections, everything is clean and overall good connection (no corrosion nor oils etc).

    Right now it's 3.09am so I'm unable to start it right now :p (damn neighbours). Anyway, I need help understanding what is what and also need guidance in relation to testing the right things.

    Below are some diagrams so I'm hoping you can tell me the number of the regulator, rectifier, generator and anything else I should be testing, and how should I be testing it?

    I'll give the rise volts measures at around 1pm tomorrow after testing.

    Also, a link to the Owners Manual if required for my model is provided after diagrams.


  10. Also guys, I asked for a quote for a second hand alternator for the Zeal from the local wreckers and they said $135.00... ah I'm wondering if this is a reasonable price for an alternator?
  11. That sounds about right, although I'd expect it to work for that money. But, as I said upthread, if you have got a charging problem (which is by no means certain), the alternator is probably the least likely culprit.