Bogging when revved quick



  • When the bike is idling and i open the throttle up quickly it bogs, runs on idle but it acts weird. When riding it seems like the powerband comes more suddenly, and not as smooth as before.
    I have checked spark plug, which is perfect and brown. I have opened the carb and the main and pilot jets where plugged, i cleaned them and still has the same bog as before. Tried without air filter. When using choke it does not bog when throttle is opened quickly.

    I'm grateful for any suggestions.



  • @Bananper Which plug are you using???



  • @NINJA br9es, never had any problems with it



  • @Bananper OK more points to check;

    1. Is the PV adjusted and performing correctly?
    2. Check Spark plug cap and HT lead for any faults?
    3. Is the coil in good order, are you getting a good spark?
    4. Are any of the jets blocked?
    5. Are there any blockages/leakages/worn pipes etc in the air flow system/inlet manifold, or is the air filter clogged up?
    6. What is the engines compression, have you checked it?
    7. Any loose nuts/bolts on cylinder head?
    8. Is the Head gasket OK?
    9. Is the cylinder head warped?
    10. Any loose joints/seals or holes in your exhaust system?

    I would check all of those and see what any of those show. If they are all good then you may have a worn piston, rings, or cylinder? Or your crankshaft oil seals may have gone? But a compression test will give you an idea of what condition your bottom end is in???



  • @NINJA it's not like ignition bogging, it feels like a carb or reed problem tbh



  • @NINJA could it be blown reeds?



  • @Bananper Perhaps - I would check the whole intake system and see what that show's? It sounds like you have a good mixture, but obviously under load aka WOT, something is not performing correctly or faulty. Check those points I listed above and see what clues you get??? πŸ˜‰



  • Sounds like it's running lean at some point with choke improving things. You need to work out what throttle position the bog occurs and try richening up the part of the carb that controls that throttle position.



  • @DTR-NSR yes +1 on this @Bananper check the rubbers make sure they’re not brittle bend them and check for little cracks that can be really well hidden



  • So i went for a ride, the bike ran as usual, maybe some rattly noises, but i didn't think to much about it. And it ran normal for a while, until i gave it some gas, suddenly i hear a whiny noise from the cylinder, i feel the lack of power, and i barely get myself home. Once i let go of the throttle the bike stops. I took out the cylinder, and i noticed that the crank was filled with coolant, and on the inlet side the piston ring was bent downwards and formed into the piston (probably why it was coolant in the crank). The cylinder has some scratches i think i will get it rebored aswell as a new piston, only thing i worry about is if that some part of the piston or ring has fallen into the crankshaft.



  • @Bananper Get yourself one of these bud, give it a good swish around the bottom end and hopefully you will pick up any loose fragments;

    https://www.ebay.co.uk/itm/Flexible-Shaft-Bendable-Magnetic-Pick-Up-Tool-With-LED-Light-And-Strong-Magnet/391962870896?epid=15017009964&hash=item5b42cec470:g:L00AAOSwR0JUO~Ya:rk:72πŸ‡΅πŸ‡«0

    Also change your oil 3-4 times within the first month after the engine is rebuilt, just to flush out any remaining debris. πŸ˜‰


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