July 13, 200818 yr My son's 04 125 is suddenly running really sluggish with slow throttle response and a lack of power. No apparent problems when he rode it last weekend. Checked the plug in normal servicing yesterday and it was perfect brown colour but thought I'd change it for a new one anyway. Did one lap of a local trial today and said it wasn't pulling properly. Checked the plug as a first step and it was really black and carboned up. Put the other plug back in and the bike is really no better. As I said it feels sluggish on the throttle and if you rev it as if you are cleaning it out there doesn't seem to be a lot of normal 2T smoke (don't know if this is connected or not). Other than change the plug nothing else has been altered or adjusted. Any suggestions gratefully received.
July 13, 200818 yr Hello When you say 'normal servicing' does this include.... Removing and cleaning the air filter. (choked filter will strangle the bike) Removing and cleaning the carb. (water or dirt, even the tiniest bit will cause problems) Remove the rotar cover and ensure it's all nice and clean and dry in there (water again normally) Change the oil (colour and appearance of regularly changed oil tells a thousand tales) Try a brand new plug, it'll take away the doubt. Still got a problem? Change the petrol and flush and clean the carb again. Check the reeds while the carb's off. No joy yet ? Delving closer to the realms of technical problems - Low compression? Remove the front header pipe (exhaust) and look for scores on the piston. It may have 'nipped' a ring Before I bore you to death, see how you get on with all that lot first ! GJ Edited July 13, 200818 yr by gjbiker
July 13, 200818 yr Author Thanks for that, oil, filter and plug were done as 'normal' so I'll have a go at cleaning the carb and a look under the rotor cover for starters.
July 14, 200818 yr Before you get too involved check these 4 items first. 1 Check the tank breather. 2 Check the rubber flap under the tank has not flipped up and covered the air intake to the airbox . You may need to punch a hole in it and cable tie it down to the engine stay.3 Try a new plug cap the black ones are known to give touble,try the red rubber ngk item.Check the fuel flow from the petrol tap.4 Check cdi earth wire ( they are a bit short) has not pulled back its pin in the terminal block and is thus making a poor connection.
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