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Help Need the MC22 brains trust

Discussion in 'Honda 250cc In-line 4's' started by kiffsta, Aug 21, 2018.

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  1. kiffsta

    kiffsta Senior Member

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    okay, I bought a mc22 a while back , it has sat for 18 months . After getting it back to the shop, we cleaned the carbs, while they were off I did a compression test and cold values were 170-190 across all 4 pots. Once the carbs were cleaned, we put in some fresh fuel, plugs and she fired up, engine sounded strong. There were a myriad of electrical mods to the harness and the indicators and high beam did not work, so I installed a known good harness and switch block. I then took it for a test ride and it rode really well. High fives all round .

    We left the bike for a few weeks and tried to start it, it wouldn’t go and Fowled the plugs, I put new plugs in and again she ran. I decided today to start it and it really struggled to start, eventually we got her going , we let her run for a bit on an aux fuel tank minus the air box, after she got warm, she conked out. I tried to start it and it took ages to start. Once warmed up, I have noticed fuel vapour coming from the muffler and the crankcase breather, I figured the carbs might be crook so I fitted another set, same issue, starts easily when cold, but conks out when hot.

    I tested the reg and it passes the diode test
    I tested the stator, ac outputs are in spec
    Battery is 12.5v at rest, 12.9 at idle, hits 14 volts at 3500 rpm
    I tested the coils, I am getting 25.1 ohms cap to cap on 1 and 4
    I tested the other coil and got 24.9 ohms cap to cap on 2 and 3
    Pickup coil measures up at 502 ohms which is in spec
    I have stripped the petcock , diaphram is working well
    Carbs have been balanced using carb tune
    Checked the carb boots, found some cracks, so I replaced with new Honda carb boots
    Fuel is fresh
    No fuel filter

    I’m at a loss, any ideas ?
     
    kiffsta, Aug 21, 2018
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  2. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    It's clearly got a fuel supply issue. I would be looking closely at the fuel tank outlets (butchered like the pink lady fzr?), fuel pump (is it dumping too much fuel?) then float height, float needles, seats, and o-rings under the seats.

    I would be swapping in a known good fuel tap and pump before anything else, everything else looks OK.

    When you say it struggles to start, is it slow to crank? When I was tuning my ZXR I didn't have a fan going to provide airflow, reg/rec got too hot and stopped working, bike conked out from lack of juice. Charged it up and unplugged the headlights, and got some airflow on the bike. All good after that.
     
    Linkin, Aug 21, 2018
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  3. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Sound's like the battery could be a bit low in capacity, at 12.5v that is about 85%-90% charged.
    when it stopped did you measure the voltage at the battery ?
    Did it foul the plug's then stop ?
    If so i reckon the battery may be on its' last leg's, and may not be able to keep up with what the bike is using/needing, if the voltage is slowly dropping the spark may get weaker and weaker till it can't ignite the air/fuel and it foul's the plugs?
     
    my67xr, Aug 21, 2018
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  4. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    GreyImport, Aug 21, 2018
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  5. kiffsta

    kiffsta Senior Member

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    No fuel pump on the mc22, petcock is vacuum operated, the vac line is capped and fuel fed from an aux tank while I nut this out

    I too am leaning towards the fuel valves, the floats on the mc22 are not adjustable , what frustrates me the same behaviour is found on 2 different sets of carbs , hence why I spent so much time testing electrics
     
    kiffsta, Aug 21, 2018
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  6. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    I have seen a couple of Honda service manual's showing the ignition coil secondary winding test done with the spark plug cap's on the lead's still.
    It work's out to be around the same total as FZR's etc,
    14,000 0hm's to 18,000 Ohm's plus the 10,000 Ohm cap = 25,000 Ohm's - 28,000 Ohm's
     
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    my67xr, Aug 21, 2018
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  7. kiffsta

    kiffsta Senior Member

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    The battery was shagged so I used one from my track bike, when that went flat, I used my jump pack, lots of amps :)
     
    kiffsta, Aug 21, 2018
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  8. kiffsta

    kiffsta Senior Member

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    • Like Like x 1
    kiffsta, Aug 21, 2018
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  9. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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    My first thoughts are as my67xr wrote that the voltage is dropping off. Try a meter on the coils to see if there is 12v at the coils and does it drop off as the engine runs and while starter motor is going. Using different carbs with same result certainly points to electrical.
     
    Murdo, Aug 21, 2018
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  10. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Buy a Yamaha


    :party:
     
    GreyImport, Aug 21, 2018
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  11. kiffsta

    kiffsta Senior Member

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    It fowled the plugs trying to start , full choke, no throttle , then maybe a small amount of throttle when it wouldn’t fire
     
    kiffsta, Aug 21, 2018
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  12. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Do the 'lay the plug on the head' trick to check the spark
     
    GreyImport, Aug 21, 2018
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  13. kiffsta

    kiffsta Senior Member

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    I have really good spark on all 4
     
    kiffsta, Aug 21, 2018
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  14. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Sometimes when coils or other electrical components are faulty they will work fine when cold. In the olden days when dinosaurs roamed the earth and we used Yamaha Electro Testers, cue Dr Who theme, we would leave the coils connected to heat up before doing tests. Same thing happens with alternators. Use an ammeter to test charge current.
    I value resistance values the same as voltage tests, which is not much better than useless.
    Picture+010.jpg
     
    maelstrom, Aug 21, 2018
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  15. kiffsta

    kiffsta Senior Member

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    I am going to add one of them to shopping list
     
    kiffsta, Aug 21, 2018
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  16. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Swap out the coils and TCI unit and see how it goes.
     
    maelstrom, Aug 21, 2018
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  17. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    I think there's more chance of it being the TCI than 2 seperate ignition coil's.
    Maybe run it again from cold till it warm's up and then dies, and check there's 12v going to the coil's still, also check there's a signal coming from the pulse coil.

    When coil winding's warm up they can expand and open up any fracture's
     
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    my67xr, Aug 21, 2018
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  18. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    Leads?
     
    Frankster, Aug 21, 2018
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  19. Wozza

    Wozza Active Member

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    Valve clearances....?
     
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    Wozza, Aug 21, 2018
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  20. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Just looked at the Service Manual, there's 2 pulse coil's to check on the MC22's.
    And the spec's are 315 0hms to 385 Ohm's ?
     
    my67xr, Aug 21, 2018
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