'10 crf250r idling issue after cam chain swap
  • Bobbycrf250r
    Posts: 2
    Joined: Tue May 16, 2017 9:22 am

    '10 crf250r idling issue after cam chain swap

    by Bobbycrf250r » Tue May 16, 2017 9:57 am

    Hello all, I've been lurking the site for a while getting answers through searches, however i cannot find a relatable answer to my issue.

    I bought a '10 crf250r a couple months ago from a guy that just had the top end rebuilt with a cylinder works top end kit. It was hard to start, i assumed it was due to my not riding for a few years and needed to relearn a couple of things. took it out to our local MX park and was riding some trails. about 2.5 hrs into it, I heard loud slapping in the top end. I immediately rode it back and loaded it up.

    Upon inspection, the cam chain was stretched and incredibly loose. Ordered a new Hot cams cam chain and manual tensioner. when I broke the engine down, got it to TDC and looked at the cam, it was 180 degrees off. I assume due to the amount of slack in the cam chain it allowed itself to spin out of timing. replaced cam chain, installed manual tensioner to manufacturer recommended specs, reinstalled the cam to coincide with TDC, checked valves, which were in spec.

    After putting everything back together, torqued according to the service manual, i tried to start it. it was still really hard to kick over, had a couple of back fires and once started, would not idle. With the high idle knob pulled out, it was idling at what i would consider normal idle speed and when high idle pushed in, it would not idle on its own. i would have to rev it up. took it for a spin, kept having to keep it revved up and when pulling back into shop it died on its own, due to low idle.

    Pulled the spark plug, it was badly fouled out and was rusted around the exterior. So when he rebuilt the top end, he kept the same plug and did not change the cam chain. Replaced the spark plug with a new factory one. Starts up a little easier, however the idle issue is still there. i tried turning the idle knob, but did not notice any real difference until i took it for a ride around the shop parking lot. it was pretty much the same thing until i pulled in the clutch to turn around. it would idle up high like it should when the high idle knob is out but would go back to normal when i let the clutch out and gave it throttle. it did that a few times, but i did not ride long as i was in a hurry to leave.

    I would appreciate any ideas anyone can give me on this topic. i cleaned the throttle body and the IAT sensor, but have not had a chance to try it since then. Thanks.
  • Bobbycrf250r
    Posts: 2
    Joined: Tue May 16, 2017 9:22 am

    Re: '10 crf250r idling issue after cam chain swap

    by Bobbycrf250r » Tue May 16, 2017 10:11 am

    here is a pic of how loose the cam chain was when I replaced it.
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