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I hope I am posting this right ok where do I start a friend of mine has just bought a 2002 dt125r got it cheap enough but it not running right starts fine idles ok but from about 5 grand it lacks power to the point that when you get to about 7 grand it’s like the bike is trying to ride through deep mud it doesn’t splutter and it doesn’t feel like it’s not getting enough fuel it’s like your just not giving it enough throttle the higher the gear your in the worse it gets the bike is fitted with DEP front and back the snorkel has been removed and the air box drilled I have been through the carb it wasn’t clean but I have seen a LOT worse I have also checked the power valve it was slightly out so adjusted it when you turn the bike on it does go through the cleaning cycle but none of what I have done has had any affect also the read switch has been moved it wasn’t far enough away so moved it even further o yea the carb is fitted with a 260 main jet that doesn’t look new so has been in there a while one thing that I did notice is the little plastic thing that goes around the main jet and pilot jet is missing don’t know what effect this would have anyone got any ideas please
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@old-boy-racer first thing I would do would be to pin the powervalve open.
Take the exhaust off and align the valve so it is flush with the exhaust port then disconnect the servo motor.
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C Calum moved this topic from General Discussion on
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Jet should be 240 bud. Boyracers (sorry) seems to think dep’s need upjetting to a richer mixture for some reason
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@old-boy-racer The more air you have through the airbox the bigger the mainjet you need. Put back to original your airbox is more than enough even for 200cc or tuned 170cc. Does your carb have power jet,if yes put 225 or 240 mainjet. Whar color is your sparkplug?
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It’s a standard 2002 Mikuni flatslide carb, no? If fitted to standard airbox? If it has a .25 pilot jet it should have a 240 main. No point trying to guess it. Tape up the airbox and put it back to standard and get it running properly. Then play with it to your hearts content
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@SpookDog cheers for that I have dropped the main jet down to a 225 it’s the closest one I had got some others on order and that has improved thing quite a bit the pilot jet in it is a 25 and the bottom end is running weak I am going to do a vacuum/ pressure test on the engine to check for air leaks but was wondering if it common to up the pilot jet or is it pointing to other issues cheers once again
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Shouldn’t need to touch the pilot as long as it hasn’t been changed before. I did have to run a wire through mine to clean dried on crap out. Check the needle, it should be 4th groove from the top. Also mixture screw should be only a 1/4 turn out on this model/year carb...
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@old-boy-racer
I’ve pretty much had the same symptoms with my sons 2002 DT. Cleaned the carb put everything back to standard and worked forward from then on. I had the luxury of a dodgy oil pump to start off with then wrong main jet caused it to splutter and cut out high up in the rev range. New oil pump and standard 240 main jet sorted that. It’s very surprising how little you need change the carb if not at all by running a different exhaust. Good luck I’m sure you’ll get it sorted !
