Athena Big Bore kit fuelling problem


  • Recently fitted the Athena 170 big bore kit onto my 2005 DT SM/R. Worked beautifully for the first two or three days and now struggles to run. Feels as if there is too much air in the mixture/not enough fuel. Tried the obvious fixes e.g. carb clean, increasing tickover etc. Runs fine with the choke on/whilst using the throttle but cuts out as soon as it’s idling. Anybody else experienced similar issues and have any ideas as to what it could be?


  • Did you rejet or adjust the carb to suit the big bore kit?


  • Yeah there was definitely a rejet carried out


  • What's the spark plug look like? Have you checked/cleaned the air filter? Is the exhaust blowing?


  • Yeah the spark plug is fine, air filter has been done recently and it’s had a new expansion chamber so the exhaust is also fine


  • Take the exhaust off and have a ganders up the port. Make sure the piston crown, rings and skirt aren't damaged.

    In my experience, the Athena kit was pretty bullet proof.


  • Managed to find it, extremely small split in the inlet manifold so it was pulling extra air into the engine. Thanks for all the help though guys!!