Won't start when hot

Discussion in 'Tech Area' started by Philct70, Mar 15, 2021.

  1. Philct70

    Philct70 New Member

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    Hi, had a chance to take 5he ct70 for a first spin at the weekend now the weather is slightly better. Not a very good first run. Idles brilliant, Fine in first gear, then bogs down under load and backfires. Once Engine is hot, it is impossible to start her up again. Gave the carb and jets a good ultrasonic and air pressure clean also thin wire for the jets. The throttle needle clip seats in the middle, the timing and mixture and spark plug look good. Appears to be running better but The fact that you can't re start once engine is hot, makes me think of valves? Any ideas would be much appreciated. Thank you
     
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  3. b52bombardier1

    b52bombardier1 Well-Known Member

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    Also makes me think of too tight valves.

    Rick
     
  4. darrel gunderson

    darrel gunderson Active Member

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    Yup.... Set them cold at .002 then check the timing with a car timing light.
     
  5. Philct70

    Philct70 New Member

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    Okay thank you, both at .002? Also, I was thinking a bit of grinding paste to make sure they sit perfect?
     
  6. darrel gunderson

    darrel gunderson Active Member

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    Yes .002 on both cold. I set them so a .002 with go through but a .003 will not..... No paste just set the clearance and verify the timing with car timing light. Then see how it runs.
     
  7. RMHRC

    RMHRC Member

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    Stator? Once they heat up they can cause the issues you’re having
     
  8. Philct70

    Philct70 New Member

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    Thank you all, anyway to check the stator? Might also do a compression test. Anyone know what I'll be looking for? I'm guessing around 100?
     
  9. Muddywater

    Muddywater New Member

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    Check for spark when it quits
     
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  10. OLD CT

    OLD CT Well-Known Member

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    Phil , I think you are on to something. When a engine is ''borderline'' low on compression, It will run a couple minutes and die once it warms up a little. That is what will happen at around 100 psi and lower. You need 150 or higher for a solid running engine.
     
  11. Philct70

    Philct70 New Member

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    Thank you for your inputs. Checked compression just with kick start and eventually got 100. Adjusted cold valves at .002. Will try more of your ideas tomorrow. Found how to check stator on YouTube. Need to get to the bottom of this, keep your suggestions coming, thank you everyone
     
  12. red69

    red69 Well-Known Member

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    Throttle wide open when compression was checked?
     
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  13. Philct70

    Philct70 New Member

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    Thank you, No forgot about that one! Will try again tomorrow
     
  14. Philct70

    Philct70 New Member

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    Hi guys, little update, got the compression up to 151psi with throttle open. Quite happy with that. Adjusted the float just before flooding point and now runs on full throttle, so that's good too. However, there is still a few seconds dead spot in the middle range. Also noticed that on full beam the engine was firing irregularly. Not too sure if it's carb, mechanical or electrical related issues or all of them! Is there any mechanical advance to adjust? And how can I check if there is enough electricity? Thanks all in advance
     
  15. Philct70

    Philct70 New Member

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    And forgot to say, adjusted the valves at 0.002 and started much better when hot. I guess I can say the bike is now 80% healthy, but I just need to find the last 20 with your help, thank you
     
  16. lukelaw1

    lukelaw1 Active Member

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    try adjusting the needle height in the slide this should change you midrange
     
  17. b52bombardier1

    b52bombardier1 Well-Known Member

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    When it is doing that mid range stumble, give it just a little choke. If it runs better, its running lean.

    Rick
     
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