Bike has trouble starting and runs rough after valve adjustment
  • bkruitwagen
    Posts: 2
    Joined: Mon Aug 24, 2020 4:34 pm

    Bike has trouble starting and runs rough after valve adjustment

    by bkruitwagen » Mon Aug 24, 2020 6:55 pm

    I did my first valve adjustment on my 2005 CRF250X. It fired up fine when cold but had trouble starting when hot hence I checked valve clearance both intake valves were out of spec. The exhaust side was fine. Below are the details.

    Clearance measured: L 0.05mm and R 0.05mm (Spec 0.12mm)
    Old shims: L 1.56mm and R 1.55mm

    Used the handy shim calculator from this website and ordered new shims both 1.475mm

    Installed the shim and replaced everything. Never moved the piston from TDC when doing the job and made sure when re-installing the camshaft that the 2 marks lined up the with top of the header. Also marked chain and sprocket to make sure the chain was going back in the same position. Re-installed cam chain tensioner (completely removed it) and torqued everything to spec.Remeasured clearance and all valves are within spec.

    Now the bike barely wants to start and it backfired once. I did not remove carb or exhaust header and neither did I remove the exhaust rocker arm. I am stumped. Any suggestions on what I might have missed?

    Thanks,

    Bart
  • User avatar
    JimDirt
    Posts: 4406
    Joined: Sat Nov 25, 2006 6:31 pm

    Re: Bike has trouble starting and runs rough after valve adjustment

    by JimDirt » Wed Aug 26, 2020 7:20 pm

    Welcome to the site !! \:D/

    Well , if it ran fine before , then it has to be something you did , so the first thing I would check is when you pulled the tank , it is possible that you inadvertently pulled the connector on the coil power wire by getting it hooked on the fuel valve as you were pulling the tank out and it is either off , or looks like it is on , but not actually connected , while the tank is off , push on the connector and make sure it is on tight .... that happens a lot and is usually overlooked ....

    If that does not fix it , then even if you are positive on the timing and fuel , that would be the next place to look/recheck is the timing , make sure ALL 3 marks are aligned , the small round plug , ignition side , the cam sprocket marks , and the large round plug on the clutch side .... , if the bike sat for a long time and the gas went bad ........to rule out any carb issue .... with the tank still off , I would pull the spark plug and pour about a teaspoon of gas down the hole , put the plug back in (without reinstalling the tank) put the plug wire back on and try to fire it , if it starts then it is a fuel issue , if not , revert back to timing ....... 8-[ :-k
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho
  • bkruitwagen
    Posts: 2
    Joined: Mon Aug 24, 2020 4:34 pm

    Re: Bike has trouble starting and runs rough after valve adjustment

    by bkruitwagen » Thu Aug 27, 2020 10:30 am

    Thanks for getting back to me! I am now pretty sure it is a timing issue and I might be a tooth off. I going to recheck timing, whenever I have a little time :)

    I will report back how it went and if that was the issue but the more I read about it the more likely it sounds. If for sure gets a spark and the gas is fresh so we can eliminate that.

    Update:
    I opened the valve cover again and ended up checking all the timing alignments and everything lines up perfectly and made no changes. Buttoned up things again and now the bike fires up and runs great. No idea what was wrong the first couple of times but I guess "third time's the charm" hold true in this case :D
  • User avatar
    JimDirt
    Posts: 4406
    Joined: Sat Nov 25, 2006 6:31 pm

    Re: Bike has trouble starting and runs rough after valve adjustment

    by JimDirt » Fri Aug 28, 2020 2:30 pm

    Could it have been a loose connection at the wire that plugs into the coil like I mentioned before ??? ... it is usually knocked loose by pulling the tank and the fuel valve catches on the wire and pulls it off or partially off , that would be my guess if it runs fine with nothing done .... :-k
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho

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