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Help Honda MC22 back from the Dead

Discussion in 'Honda 250cc In-line 4's' started by r1rmu13, May 13, 2018.

  1. r1rmu13

    r1rmu13 Member

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    Hi All,

    About 6 months ago I picked up a badly cared for MC22,

    I Have rebuilt the bike apart from a major engine strip, has anyone had an issue where as the bike won’t start after the following:

    Now has 4 good sparks
    Good compression
    Fuel good too

    But won’t start

    Question I have is; can you have 4 good sparks and still have a faulty pulse generator?

    IE I believe its firing at the wrong time?

    The online available service manuals do not discuss in detail the pulse coil in enough details for me to understand it’s interface with the CDI unit

    Cheers
    Richard
     
  2. GreyImport

    GreyImport Administrator Staff Member The Big Cheese Contributing Member

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  3. r1rmu13

    r1rmu13 Member

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    Hi there,

    Thanks for the speedy reply, yes they are connected correctly, as per the workshop manual

    It’s the N model

    I’m still thinking its the timing of the spark? Which I believe is sychonized by the pulse generator/cam ?
     
  4. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    Do an ohms reading on your pulse coil , just unplug from your harness and measure between the 2 wires
     
  5. r1rmu13

    r1rmu13 Member

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    Yes I had checked it and found to be 420 ohms, so looks good

    I found a good article on the pulse generator so checking the physical set up , just drained the oil to get at it

    I’ve answered one of my original questions, you do not get a spark if it’s faulty, proved this by disconnecting it

    Thanks for your help

    I will be taking the left side cover later today, and will know more then
     
  6. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    If you have the hooked up the spark plug leads wrong then it will backfire
     
    Last edited: May 13, 2018
  7. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    Left hand coil is 2 and 3 , right hand coil does cyl 1 and 4

    F4438785-86C2-41F6-95F7-0ECA7F2F23C6.jpeg
     
  8. r1rmu13

    r1rmu13 Member

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    Yep must have checked 20 times or so

    Plus made up a new set of NGK plugs and leads all new, New Iridium plugs, 4 heathy sparks too

    You hear it blow back through the exhaust but won’t fire up
     
  9. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    Have you pulled the carbs off ?
     
  10. r1rmu13

    r1rmu13 Member

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    Yep about 3 times now

    Cleaned jets, new insulators New clips and sealed

    New air filter, new needle valves in case Of leakage

    Done a compression test but then not cold 180 170 170 182
    So no differential of more than 15 psi what they s would equate to warmed up not sure but suffice to start?

    Cheers
     
  11. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    Have you tried starting it with the tank off,
    Block the vaccum hose on cyl 1 and use an aux tank, your petcock may be shagged/ blocked so this may help rule it out

    Your comp readings are pretty good.

    When you cleaned the carbs, did you remove adjust the air fuel mixture screws ? If so, how many turns do you have them set to ?
     
  12. r1rmu13

    r1rmu13 Member

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    Yep running Aux tank suspended over the bike with inline filter so you can see the fuel

    Yep set the mixture screws @1 3/4 turns out plus new o rings
     
  13. r1rmu13

    r1rmu13 Member

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    Any tips on staying logged in yep have ticked the stay logged in box or do you have to be a premium member ? Cheers
     
  14. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    Hmm, you should stay logged in if you tick the box , back to your bike, do you know what year it was made ? If yours is 94 onwards (cbr250rr r ) then the carbs should be set at 2 and 1/4 turns out

    You can your frame number against this list
    DF3D3BCF-CEAE-4246-8CF6-C03BDB0755E8.png
     
  15. r1rmu13

    r1rmu13 Member

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    Hi there,

    No I tick the box every time and still have to log in (Iphone 6)

    Back to the bike

    Found bike carbs 1 2 3 on 1 1/2 and 4 completely wound in? Yep that’s how I found them

    These are the settings taken from 2fiftycc;

    CBR250(F) + CBR250R(H): 2Ѕ screws
    CBR250R(J+K) : 1 5/8 screws
    CBR250RR(L+N) : 1 3/4 screws
    CBR250RR® : 2 1/8 screws

    So I set as 1 3/4 as standard and am running standard jets

    So not sure where you got the 2 1/4 turns out?

    I have now removed the side cover and all is well, pulse generator is set correctly

    So I’m now left with perhaps the cdi unit?

    So about to do some reading to see what in the past owners fault issues for changing

    Cheers for your help much appreciated
     
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  16. Murdo

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

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    Have you got the wires going to the coils on the right coils?
    Swap them over and give it a try (don't ask how I found this out).
     
  17. r1rmu13

    r1rmu13 Member

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    Yes all correct, also the loom for the left coil does not reach to the right coil, and checked by the WSM

    Thanks for your input
     
  18. Murdo

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

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    Put a timing light on it and see where the plugs are firing on the flywheel.
     
  19. r1rmu13

    r1rmu13 Member

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    Apart from getting a voltage peak adaptor to totally confirm the pulse generator .91v and the ignition coils 178v all looks well with the CDI unit, have no way of confirming the timing of the sparks discharged without another CDI unit to swap out that is

    So going to spend some time rechecking the amount of fuel getting to the compression chambers

    The weird thing is the way in which it pops back through the exhaust, it’s not a proper bang misfire it’s almost like like a mortar being launched then sound like it runs back up the exhaust? Odd
     
  20. r1rmu13

    r1rmu13 Member

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    I would but I cannot get it to run - cheers
     

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