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Thread: Trouble with very old Honda HR 21 (GV 150) 1978

  1. #1

    Trouble with very old Honda HR 21 (GV 150) 1978

    Hi there,

    I have some problems with our old and trusty HR 21. I do not want to give it up, despite it's age !

    Trouble is that it uses to develop a lot of coal on the spark plug, and then it dies after a while.

    I have taken the head of, checked the valves and they look fine to me.

    I have cleaned and checked the carburettor, and it looks clean and nice to me.

    What puzzles me is "how to adjust the carb". Is there a manual other / better than the green Honda service book I bought on ebay ? It does not really describe how to fine -tune it. It does not really react on the rear small setscrew (with the spring under it, the "idle screw").

    When I manage to get it to run (on a fresh new BP ... 6 NGK plug), then it does a sagging noise- revs up and down, up and down, it changes every second. Wrrrr,wwwwwrrrrr, wwwrrrrr. Like a saw.

    What can I try next ? I tried new fuel.

    And I tried a Colourtune glass spark plug (I have a lot of old car experience so I thought it might work here, too), but this was fouled / covered thick in black deposits within a few seconds so it stopped running !

    So: Why is it running so rich, what can I do ?

    Many thanks for any help !

    Carsten

  2. #2

    Re: Trouble with very old Honda HR 21 (GV 150) 1978

    could be the coil does it seem worse after it runs for awhile note u can mod a 5hp briggs coil instead of paying the honda price.

  3. #3

    Re: Trouble with very old Honda HR 21 (GV 150) 1978

    Dear Thread,

    Sorry for my 'english'. I hope you understand my text. Oder schreibe ich besser in deutsch?
    I have the same kind of problem. It started suddenly. When the engine is warm it dies or starts running very unregelar. It sounds like it has combustion while one or both valves are open (sound like a gun shot). Valves margin is OK. Do you think ignition coil is the reason? How to solve this problem?
    Looking forward to your answer. Thank you in advance. Best regards from Holland,

    WPW

  4. #4

    Re: Trouble with very old Honda HR 21 (GV 150) 1978

    Here's a link to a picture diagram and parts for the Honda HR21 mowers,look at items #7 and #8, make sure the small holes are clean and not obstructed use a small wire to clean the holes then use compressed air to blow out any debris. If you don't have an air compressor use small can of compressed air. I would even soak the carburetor for an hour or so in carburetor cleaning solution then dry everything off with compressed air. Good Luck.

    All Years HR21 PDA LAWN MOWER, JPN, VIN# HR21-1000001 TO HR21-1051093 Honda Lawnmower CARBURETOR Diagram and Parts

  5. #5

    Re: Trouble with very old Honda HR 21 (GV 150) 1978

    Quote Originally Posted by Streamlight View Post
    Here's a link to a picture diagram and parts for the Honda HR21 mowers,look at items #7 and #8, make sure the small holes are clean and not obstructed use a small wire to clean the holes then use compressed air to blow out any debris. If you don't have an air compressor use small can of compressed air. I would even soak the carburetor for an hour or so in carburetor cleaning solution then dry everything off with compressed air. Good Luck.

    All Years HR21 PDA LAWN MOWER, JPN, VIN# HR21-1000001 TO HR21-1051093 Honda Lawnmower CARBURETOR Diagram and Parts
    Welcome to all the new people here. I think it's a carb issue as well. Thanks to the previous poster (Streamlight) for that link!

  6. #6

    Re: Trouble with very old Honda HR 21 (GV 150) 1978

    Here's another link with videos on cleaning honda carburetors.

    Honda Engines Europe EEC

  7. #7

    Re: Trouble with very old Honda HR 21 (GV 150) 1978

    Forgot to mention, click on the 'service' tag and then service movies.

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