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Thread: Hornet CB250 starting issues

  1. #16
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    18th October 2018 - 15:38
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    Quote Originally Posted by pete376403 View Post
    Is the choke on this model another butterfly in the mouth of the carb? The diagram I am looking at shows a "valve set, starter" which looks more like a normal plunger. However given that there are probaly a hundred different models of 250 hornet...

    https://www.bike-parts-honda.com/hon...E_17_1/1/22978
    Here's the correct one.

    https://www.bike-parts-honda.com/hon...061/E_17/1/909

  2. #17
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    Quote Originally Posted by FJRider View Post
    The Choke is reduce air-flow through the carb. Increasing the amount of fuel in the fuel-air mixture that is going into the carb.

    If it dies when the choke is off ... that indicates not enough fuel is getting to (or through) the carb.

    The Petcock may be the issue. If the normal ON setting is being used ... try the reserve or Run setting so fuel should flow all the time. This can be checked by turning it to OFF. Then pull the line off the carb and trying both on and the run/reserve setting and see how good the fuel flows. If it has a vacuum line ... with no off setting ... you might need to suck on the vacuum line to get the fuel to flow. If it has a vacuum line ... THAT in itself may be the issue if the line is not attached (or blocked. or attached at the wrong place) to the carb.

    This will/might confirm if the issue is in the carb or Petcock/tank area. Unless you know what you are doing ... pulling the carb apart can go badly.

    Old adage with old bikes ... try the simple things first and hope ...
    it does start on both res and on, but with the choke on. I'll pull the fuel line off - then see how it runs on both 'on' and 'res'. Thank you.

  3. #18
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    Quote Originally Posted by mnishi View Post
    The bikes done 29,000kms and is a 1997 model.

    As an update, still waiting on the air filter today - but I've been starting the bike with choke and it goes ok, if I hold the revs and take the choke off, it also goes ok, it doesn't just die easily. If I keep giving it some gas, it runs, but of course as soon as I let throttle go, it turns off.

    So I forgot to mention, off the carbs there's these two hoses that are coming down. When I removed the air box thing, it was just hanging there. Do these two hoses connect to anything?

    Also, there's another pipe that runs from the right side of the tank, and also goes no where. Where is this meant to go?

    Added photos!

    Thank you
    The one off the tank might be an overflow drain for around the filler cap on the tank that drains it to the ground.

    Is the one in image two connected at the other end from your finger to the carb .. ??? Is there a spare "Outlet" on the petcock .. ??

    With the age of the bike ... I would have thought a vacuum line would be fitted.

    And at 29,000 km's ... unless the bike has been SERIOUSLY abused ... I doubt that compression issues are the problem.
    When life throws you a curve ... Lean into it ...

  4. #19
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    Quote Originally Posted by mnishi View Post
    Diagram's list parts numbers 38 and 39 (listed as Tube for both) are suspiciously similar to fuel line and vacuum line.
    When life throws you a curve ... Lean into it ...

  5. #20
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    Quote Originally Posted by FJRider View Post
    The one off the tank might be an overflow drain for around the filler cap on the tank that drains it to the ground.

    Is the one in image two connected at the other end from your finger to the carb .. ??? Is there a spare "Outlet" on the petcock .. ??

    With the age of the bike ... I would have thought a vacuum line would be fitted.

    And at 29,000 km's ... unless the bike has been SERIOUSLY abused ... I doubt that compression issues are the problem.
    Yes, it does go to the carb.

    There is just two lines from the petcock - vacuum line and a fuel line.

    So the vacuum like goes to the centre of the head it seems (image 1). You can just make out where its going.

    The fuel lines goes to the centre of the carb.

    (image 1 showing vacuum line connected the head)
    (image 2 showing fuel line connected to carb)
    (image 3 showing petcock)
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  6. #21
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    Quote Originally Posted by FJRider View Post
    Diagram's list parts numbers 38 and 39 (listed as Tube for both) are suspiciously similar to fuel line and vacuum line.
    That looks about right... they're currently just dangling off, any idea where they should be connected?

    Thanks

  7. #22
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    Quote Originally Posted by mnishi View Post
    Yes, it does go to the carb.

    There is just two lines from the petcock - vacuum line and a fuel line.

    So the vacuum like goes to the centre of the head it seems (image 1). You can just make out where its going.

    The fuel lines goes to the centre of the carb.

    (image 1 showing vacuum line connected the head)
    (image 2 showing fuel line connected to carb)
    (image 3 showing petcock)
    The vacuum line should go to the CARB (from the petcock).

    The hose attached to the center of the Head should be a breather hose for the top of the engine to go down below the engine to drain out to the ground. Usually gasses and a few spotty bits of oil (at worst) come out. This is so the top end of the engine (camshafts and top of the valves) does not pressurize.

    Connect the vacuum line to the carb and the line from the top of the head down and behind/below the engine. Preferably to the side and away from the rear wheel centerline.

    Then see how it goes.
    When life throws you a curve ... Lean into it ...

  8. #23
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    Look at this diagram https://www.bike-parts-honda.com/hon...061/F_14/2/909
    Item #10 is the main fuel supply to the carbs. refer to diagram E-17 to where that connects. All carbs will connect together with a pipe, one of which will have a T for the fuel pipe to connect to
    Item #19 is the vacuum line to opens the fuel when the engine is running. Refer to E-2 to see where that connects. This will be a connector on the inlet manifold, between a carb and the cylinder head. When the engine cranks and creates vacuum in the intake, the diaphragm valve on the fuel tap open and allow flow to the carb bowls

    There will also be an overflow pipe from the carb, as stated keep this out of direct line of the tyre
    it's not a bad thing till you throw a KLR into the mix.
    those cheap ass bitches can do anything with ductape.
    (PostalDave on ADVrider)

  9. #24
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    Quote Originally Posted by FJRider View Post
    The vacuum line should go to the CARB (from the petcock).

    The hose attached to the center of the Head should be a breather hose for the top of the engine to go down below the engine to drain out to the ground. Usually gasses and a few spotty bits of oil (at worst) come out. This is so the top end of the engine (camshafts and top of the valves) does not pressurize.

    Connect the vacuum line to the carb and the line from the top of the head down and behind/below the engine. Preferably to the side and away from the rear wheel centerline.

    Then see how it goes.
    Ok, so I didn稚 really understand that diagram a whole lot..

    So I値l connect the vacuum pipe from the petcock to the carb, I値l search for where this might connect...

    As for the breather pipe, I値l search for this also.

    Will update some time tomorrow!

  10. #25
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    Quote Originally Posted by pete376403 View Post
    Look at this diagram https://www.bike-parts-honda.com/hon...061/F_14/2/909
    Item #10 is the main fuel supply to the carbs. refer to diagram E-17 to where that connects. All carbs will connect together with a pipe, one of which will have a T for the fuel pipe to connect to
    Item #19 is the vacuum line to opens the fuel when the engine is running. Refer to E-2 to see where that connects. This will be a connector on the inlet manifold, between a carb and the cylinder head. When the engine cranks and creates vacuum in the intake, the diaphragm valve on the fuel tap open and allow flow to the carb bowls

    There will also be an overflow pipe from the carb, as stated keep this out of direct line of the tyre
    How do I know where E-2 connects?

  11. #26
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    Quote Originally Posted by mnishi View Post
    So I値l connect the vacuum pipe from the petcock to the carb, I値l search for where this might connect...

    As for the breather pipe, I値l search for this also.

    Will update some time tomorrow!
    The vacuum hose and breather hoses (and fuel hose) are usually different diameters, So there should be little (no) confusion about which is which.

    However ... the unknowing can often MAKE them fit. Resulting in having problems similar to yours.
    When life throws you a curve ... Lean into it ...

  12. #27
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    Quote Originally Posted by mnishi View Post
    How do I know where E-2 connects?
    In diagram E14, there are 4 T pieces (item 5, 7, 9 & 10) which hoses could connect to. If the diagram is to scale, 9 looks bigger so thats *probably* the crankcase breather, if it is the same diameter as the breather attachment on the top of the cam cover (diagram E1, arrow out going out to F17).
    I think 7 is the fuel inlet because its going to diagram f14, the fuel tank. 5 looks like it attaches to a hose pointing downward so *probably* a carb float bowl overflow drain, which leave 10 as the vacuum source to the fuel tap. You've probably worked this out already, but diagrams Exxx refer to engine, Fxxx refer to frame, ie everything else


    Hold up! Another look. the crankcase vent in the top of the cam cover goes to the air filter case diagram F17, and the T connector 9 in the carbs as above goes to another breather valve in the air cleaner (also diagram F17.)

    Disclaimer I have never been close to a hornet 250 :-)
    Last edited by pete376403; 11th February 2021 at 21:27. Reason: added a bit more
    it's not a bad thing till you throw a KLR into the mix.
    those cheap ass bitches can do anything with ductape.
    (PostalDave on ADVrider)

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