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Solved Strange engine failure - ZXR250-C

Discussion in 'Kawasaki 250cc In-line 4's' started by DanoHosko, Nov 9, 2024.

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  1. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    Plugs you should be able to de-pin them and there are a multitude of suppliers for new pins.. then they just pop back together just like Factory.
     
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    Andych, May 1, 2025
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  2. DanoHosko

    DanoHosko Well-Known Member Premium Member

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    I do have a couple of old ones at home to be fair haha, i was thinking completely new connectors would be ideal but not necessarily feasible i guess!
     
    DanoHosko, May 1, 2025
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  3. DanoHosko

    DanoHosko Well-Known Member Premium Member

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    Ah good to know they are common pins then, I'll see what i can dig up!
     
    DanoHosko, May 1, 2025
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  4. DanoHosko

    DanoHosko Well-Known Member Premium Member

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    Ok so 14.5 - 14.8V up to 18krpm, at around 18krpm I'm getting 18V ++

    https://youtube.com/shorts/v9qPAPQP4KA?si=O1Kb9ucGmLo5bzvM

    I'll chuck on my new spare reg/rec and see how it looks!


    On a side note, I have three CDI boxes:

    21119-1322 (J) - I believe this is the 45hp C model (in service)
    21119-1384 (B) - I believe this is the 39hp C model
    21119-1316 (K) - I believe this is the Malaysian C model? 45hp / 240kph?
     
    DanoHosko, May 2, 2025
    #24
  5. DanoHosko

    DanoHosko Well-Known Member Premium Member

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    Tested the old rec/reg:
    White - Yellow = Open circuit
    Black - Yellow = 0.47

    New rec/reg:
    White - Yellow = 0.147
    Black - Yellow = 0.46

    14.4V from 2krpm to limiter. Happy days!

    @Linkin , do you think the dodgy rec/reg could possibly have contributed to the starter relay burn out issues, or I need to do some more chasing on that one?

    I don't appear to have an actual high battery voltage when it's off (so when starting).

    Seems the old rec/reg was possibly only giving me half-wave rectification, and also poor regulation?
     
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    Last edited: May 2, 2025
    DanoHosko, May 2, 2025
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  6. Linkin

    Linkin The Mechanic - Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    It could have contributed, I won't say it was definitely the cause of the problem though.

    Do yourself a favour and upgrade to an FH020AA MOSFET regulator and buy a connector kit. Can get a 2nd hand one if on a budget, otherwise buy from Roadstercycle in the US. Bypass the main wiring harness due to age and potential issues. 3 wires from stator to reg and battery positive / earth. Put a 30A fuse or auto reset circuit breaker in line on the positive side.

    MOSFET reg is much more efficient and outputs less waste heat, which is an issue with the ZXR reg due to its location. To this day, I have only seen ONE dead FH020AA which was caused by (get this) engine oil wicking up the stator wires and into the plug for the regulator, which also had a broken retaining clip due to some ham fisted monkey using a screwdriver to pry it off.

    Series regulators (SH775, SH847, but NOT SH821 which is a standard diode reg) are even better again, they do not run the stator at 100% all the time like diode and mosfet regs do, you will never burn out a stator using a series regulator. But they are expensive and bulky.

    Just beware with the ZXR you will have to tap one wire into one of the stator wires near the reg to run the headlight relay, I forget which one but check the manual for the wiring diagram. ZXR's run a 6 wire reg where most other bikes are 5.

    You may run into battery drain issues as I did on my ZXR though, but that was with an SH847
     
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    Linkin, May 2, 2025
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  7. DanoHosko

    DanoHosko Well-Known Member Premium Member

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    Wicked, great advice as always!
    I'll look into a proper upgrade for the rectifier rather than these eBay specials, better to spend extra on a decent one than having to replace burnt out components down the line

    Not too fussed about the headlights, as it is they were planned staying disconnected for now anyway, saying that, if there is less load on the reg even though the stator is still used at 100% as you say, that means the regulator needs to dissipate more as heat?
     
    DanoHosko, May 2, 2025
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  8. Linkin

    Linkin The Mechanic - Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    With a diode or mosfet reg, the stators are run at 100% at all times.

    The amount of heat dissipated depends on the electrical load. So if the regulator is supplying 30A (in 12V) but only 20A is being drawn by the bikes systems, you have 10A being dissipated as heat. The headlight is often the highest load on the bike, so leaving it disconnected can cause a regulator to overheat more quickly than normal.

    So less electrical load puts more stress on the regulator as it has dissipated any unused current generated as heat.

    That's why the series regulators are great, you can disconnected everything unnecessary and you won't risk cooking the regulator or stator.
     
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    Linkin, May 2, 2025
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  9. DanoHosko

    DanoHosko Well-Known Member Premium Member

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    Ok so, according to the manual, with the stator unplugged I should get 25VAC across each phase, mine passes that test
    However it doesn't mention the voltage when plugged in (to the rec/reg), I'm only getting about 8V across each phase when it's plugged in

    Is that to be expected? Or am I getting volt drop?

    The revs also drop a little when I plug it in


    Basically my headlights are not working currently either, and I think it needs the 25VAC to activate the little relay in the fuse box?
     
    DanoHosko, May 3, 2025
    #29
  10. DanoHosko

    DanoHosko Well-Known Member Premium Member

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    Ok all good...

    Looks like the headlight relay in the fuse box was blown, and potentially pulling the voltage down

    Quick solder job, reading 12VAC across phases when plugged in, and headlights are working

    Part number for the replacement relays is: NT73-2C-10

    I bought a handful a few months ago

    20250503_164511.jpg
     
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    DanoHosko, May 3, 2025
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  11. Linkin

    Linkin The Mechanic - Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    Stators are not tested when the AC windings are plugged in.

    ZXR will turn off the headlight when there is insufficient charging voltage using the standard style 6 pin regulator

    It's normal for revs to drop a little when plugging stator back in as it is an electromagnet, the magnetic field affects engine rotations, particularly on small engines, but even occurred on my R6.

    as @my67xr has noted, those NEC headlight relays are rare and not used on a lot of things, he posted up some replacement relay numbers to the forum in my ZXR thread
     
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    Linkin, May 3, 2025
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  12. DanoHosko

    DanoHosko Well-Known Member Premium Member

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    Thanks as always master Linkin, concise information

    Fingers crossed that's me sorted for a while again!
     
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    DanoHosko, May 3, 2025
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  13. DanoHosko

    DanoHosko Well-Known Member Premium Member

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    Well, the problem persists...

    From one of my videos, someone spotted that the temp sensor also drops to 0, I believe that rules out all of the ignition and kill switch circuit, as the kill switch doesn't affect the temp sensor.

    So narrowing it down, loss all power, loss of earth, or loss of key ignition switch?

    The fault also seems to have become a hard cut completely, whereas originally the revs would do some weird bouncing prior to cutting out

    I have a volt meter installed, and it reads bang on 14.5V non stop, but that is installed directly to the battery, but that tells me the charging circuit is fine now

    I'm going to chase out all the earths this weekend


    Just to recap, have replaced the following components while fault finding this issue:
    - Stator (used)
    - Battery (new)
    - rec/reg (new)
    - wiring loom (used)
    - pickup coil (used)
    - ignition coils (new)
    - spark plugs (new)
    - spark plug caps (new)
    - ignition leads (new)
    - Ignition Box TCi (used, and then swapped back to original)
    - fuse box (used)
    - cleaned out kill switch, resoldered


    Things to check:
    - all earths
    - key ignition switch
    - bypass kill switch





     
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    Last edited: Jun 27, 2025
    DanoHosko, Jun 27, 2025
    #33
  14. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Just a total guess .... but is the RR still located under the tank in its original spot? .... it must be getting super hot when hammering around the track and I think youve mentioned u dont have the air ducts fitted ..... can they even "cut out" when overheated , then return to "working" when cooled down ? .... no idea !
    Relocate it to somewhere in the open :idk:
     
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    Last edited: Jun 28, 2025
    GreyImport, Jun 28, 2025
    #34
  15. DanoHosko

    DanoHosko Well-Known Member Premium Member

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    It is in the original spot yep, this is a new one though, and I have re-fitted air ducts

    Also the bike will run with the RR disconnected, until the battery goes flat I guess


    Today though I have pulled apart the ignition switch and found a faulty 12V wire and some crusty looking solder, so replaced all the wires and resoldered so I'm hoping that might have been the cause

    Worth noting that disconnecting the fuse box and the RR has no affect on the temp gauge, whereas the ignition switch does

    Fingers crossed!!

    20250629_111707.jpg 20250629_113054.jpg
     
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    DanoHosko, Jun 29, 2025
    #35
  16. DanoHosko

    DanoHosko Well-Known Member Premium Member

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    Well glad to say this is finally fixed, seems that the ignition switch wiring was the problem, managed all 5 sessions at the track today without any cut-outs!

    Big thanks to everyone who has helped narrow it down
    Good to see the back of that gremlin :thumb_ups:
     
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    Last edited: Jul 9, 2025 at 11:53 PM
    DanoHosko, Jul 9, 2025 at 11:31 PM
    #36
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