Wont start with spark and fuel!
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Thread: Wont start with spark and fuel!

  1. #1
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    Post Wont start with spark and fuel!

    I know this a cliche question on here but please bear with me


    I bought the motorcycle not really knowing what went on with the previous owners, so history is not available.

    I redid the carbs and got ii to spark, I also bought new spark plugs.

    This is the weird part- The bike basically has the necessary to run on at the moment. Like no switches etc. Is it then safe to assume of I still get spark I have connected everything up I need? Because it does have spark??

    So without taking the engine apart- How can I fix this? Im really stumoed and I also allready followed the checklist on the bike wont start. I do know my fair share of engines.

    Upon adding some fuel to the carburetors directly you can year backfire in the exhaust pipe. I cranked it so long it was warm from backfiring but no start. I felt all 4 pipes were warm so there is no problem with the spark delivery too.

    I dont want to sell this motorcycle because I cant fix it.. Please help!

    cbr 250 mc19 1989 or 1988 not so sure

  2. #2
    Biker Slipry's Avatar
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    check spark timing - back firing into the exhaust means spark is firing on down stroke and not up. check your leads are right.

    if you have fuel air and the correct spark it should try and run
    Quote Originally Posted by schultzy View Post
    I stuck a battery up my arse.
    Yeah, that's a cool story...

  3. #3
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    How would I go about checking and changing the spark firing position? And for the coil leads, one coil does 1 and 4 and the other does 2 and 3.

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  5. #4
    Biker Slipry's Avatar
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    might have to do a bit of a search on lead position and firing order - it have been commented on a number of times, the exact specifics however escape me.
    Quote Originally Posted by schultzy View Post
    I stuck a battery up my arse.
    Yeah, that's a cool story...

  6. #5
    Biker phreak911's Avatar
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    While you're at it, do a compression test too.
    Saint by Day... Sinner by Night!

    Quote Originally Posted by banana.logic
    Your mum affects my sag.
    Quote Originally Posted by Matt
    What. the. fuck.

  7. #6
    Senior Biker Lane's Avatar
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    Pouring fuel down carbs does not provide the correct mix that your old tired engine can ignite, your engine needs atomised fuel at the right amounts to help fire the sleeping slug.

    Try it in a spray bottle perhaps? Or better still get a can of Aerostart, where are you located?

    I'm not convinced your carbs are operating 100%.

  8. #7
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    Can someone refer me to lead position and firing order? Also, the coils were removed and I reconnected them. Is there a certain wire configuration polarity on the coils? At the moment I have tried switching the lead from the 2 and 3 between to the 1 and 4 but with no avail.

    Compression test is a bit difficult seeing that I don't have a compression tester. I have felt on the intake ports and I do get a suction, but I know this is not sufficient to say compression is good.

    The reason why I haven't bought a compression tester is that I'm a student and most of the time money is a bit short and motorcycles are my passion and I love working on them, so I buy tools as time goes by but at the moment money is a bit tight.

    Would it be worth the investment to buy a compression tester at the moment or is there other things I can fiddle with?

  9. #8
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    I have actually had some petrol in a spray bottle and tried that. But next when I'm tinkering again I'm trying some lighter fluid in a spray bottle? That has a higher ignition potential.

    Why are you not convinced my carbs are good?

    I'm located in a far away country in South Africa in the Western cape ( The furthest lower point of Africa) and no, I don't ride lions and surprisingly I am white as some people are surprised there are white people here. :P

  10. #9
    Biker phreak911's Avatar
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    I wouldn't go any further until you've done a proper compression test. It'll tell you whether your motor is in good condition, so you'll know if your problem is internal or external.

    Looking at the coils from a seated position on the bike, the left coils left outlet goes to the left (number one) cylinder, the right output on the left coil goes to the far right (number four) cylinder. The right side coils left output goes to the second cylinder from the left (number two cylinder), and the right coil right output goes to the third cylinder from the left (number three cylinder).

    But seriously, do a compression test first. If you're sure you've got good spark and fuel flowing through the carbs (even if the carbs are out of balance or not tuned perfectly), then the only other things that could be preventing the motor from firing are compression and / or ignition timing. Because the only timing adjustment (generally) on these bikes is by repositioning the camshafts relative to the Top Dead Centre marking on the flywheel, you can rule timing out if you know what you're doing fairly easily. Thats why I recommend a compression test. Hope this helps!
    Saint by Day... Sinner by Night!

    Quote Originally Posted by banana.logic
    Your mum affects my sag.
    Quote Originally Posted by Matt
    What. the. fuck.

  11. #10
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    I got the motorcyle with the coils removed. Can one of you just check on the motorcycle which colour wires Goed toe which side of the coils ex. "left coil" left input wire is green and right input whatever. This will help my a great deal

    I will get a compression tester and see what's going on. Previous owner told me he believes its fine but I'll have to see. Only logical thing is the firing order. Is there a detailed post on how to set the cams timing correctly? If so can someone please give a link, still new to this forum and my way around it isnt the best.

    Thanks for the replies. Always nice to get new hope for a project in progress.

    If I get it running I'm doing a complete restore with redoing all fairings, switches keeping clusters and respraying frames too. Looking at a matte black finish and adding some honda stickers as a finish.

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