Wont start-backfires
  • AggiesaurusRex
    Posts: 1
    Joined: Sun Feb 25, 2018 2:55 pm

    Wont start-backfires

    by AggiesaurusRex » Sun Feb 25, 2018 2:58 pm

    I have a 2008 CRF250R, and this bike WILL NOT run. Not with kicking your leg off, not with push starting. Every few kicks it'll backfire out of the airbox and that's all it'll do.
    Has new cam chain, hot cam, piston ring.
    I have checked, rechecked, reset, rechecked, disassembled, reassembled, and set timing for days and this thing will still only backfire. PLEASE HELP!

    Things that have been checked:
    Flywheel and woodruff key, no damage to key
    Cam chain tensioner changed to manual, its not too tight or loose
    Piston ring set right and staggered,
    Timing is set to match on right side timing mark, left side flywheel hashes, and cam lobs are back and matched with the top of the head, and TDC was verified while setting.
    Valves are within 0.005, exhaust is a 120 and the smallest shim so I can't get it and closer.
    Wiring harness replaced, grounds cleaned, connections cleaned, spark plug replaced.
    I'm completely at a loss and open to any ideas you guys might have.
  • Back2-2
    Posts: 1148
    Joined: Tue Jan 04, 2011 3:31 pm

    Re: Wont start-backfires

    by Back2-2 » Sun Feb 25, 2018 5:10 pm

    Hello, it looks like you covered it well on checking all the ignition items. What about a simple blocked pilot jet from sitting while the bike was down for the repairs ? Carb problems can easily seem like ignition problems.
    Neil
    Black Hills of SD
    Life without Motorcycles would just be boring, really boring
    Honda 450X. Yamaha Tracer GT900. HD Fat Boy. Triumph Bonneville. Yamaha Majesty 400. Yamaha Grizzly. Yamaha Wolverine. Yamaha TW200

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