Have I missed something?
  • Harry1234
    Posts: 4
    Joined: Tue May 15, 2018 5:28 am

    Have I missed something?

    by Harry1234 » Tue May 15, 2018 10:33 am

    Hi, first time on a forum so apologies in advance as I'm sure many of you have answered these questions many times. Right here goes, my son has a 2007 twin pipe crf 250 r, he has only had this 1 month and been out twice, We bought it as a non runner and told it had dropped a valve and smoked a lot so we replaced the intake valves, (one was only bent very slightly and no piston damage) springs collets stem seals and piston rings using genuine Honda parts. Re shimmed it to spec on inlet and exhaust valves and it started really well.it used to start fine from cold but a bugger when hot.last week he went out on it and took nearly an hour to restart it from hot however run lovely but was hard to kick so we decided to investigate.the shims were still in spec but the timing had jumped 1 tooth so to be on safe side we replaced timing chain and auto tensioner with again genuine parts, new spark plug and now won't start at all, we have cleaned carb and checked jets and seem to be fine, am I missing something? Thanks in advance if anyone has any ideas.
  • User avatar
    JimDirt
    Posts: 4406
    Joined: Sat Nov 25, 2006 6:31 pm

    Re: Have I missed something?

    by JimDirt » Tue May 15, 2018 11:32 am

    Welcome to the site !! \:D/

    I guess the first question is , Do you have a Manual ??

    If so the procedure is there to guide you thru the timing process , follow it EXACTLY ....... If not , then what you need to make sure of is

    1) That you are on Top Dead Center on the piston/crank , so the mark behind the small round plug on the Ignition side cover is aligned with the mark on the flywheel

    2) The cam gear marks are aligned horizontally with the head , like so - - , and the lobe on the cam is facing backwards at about the 2-O'clock position looking from the ignition side

    3) The marks behind the Large Round plug on the Clutch side has the Arrow/Triangle and mark aligned

    If you have all 3 of these points aligned , then by hand (using the kick start with your hand with the spark plug out) turn the engine over several times till the cam lobe is facing back again , then re-check ALL your marks , they should be all aligned still (this is with the tensioner installed) , if all are aligned and still no start , then check the coil wire main lead , it plugs into the coil and sometimes removing the tank you can unplug it , if they are not aligned then you are most likely 1 tooth off and will have to redo the procedure......

    I am somewhat concerned that you mentioned the valve was bent but no piston damage , as the only way the valve can bend is to either have debris fall down the port getting stuck in the valve seat between the valve and the seat , OR , that the valve did in fact hit the piston and your just not noticing the mark ,,,, my concern then would be will the rod bearing fail quickly , as it is soft and any impact to the piston from the valve usually will result in a rod bearing failure either right away or soon afterwards , if it did happen , then you might be looking at replacing the crank .....so just a heads up to keep a ear out for knocking or paying attention to the engine turning over extremely hard at certain points during rotation , or seizing up completely ....but "usually" when the valve and piston meet , its usually not a good thing for the rod bearing 8-[ [-oo

    Report back with findings .... ;)
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho
  • Harry1234
    Posts: 4
    Joined: Tue May 15, 2018 5:28 am

    Re: Have I missed something?

    by Harry1234 » Tue May 15, 2018 12:21 pm

    Thanks for reply, all timing marks line up after repeating the cycle a few times, when we removed the head one valve was slightly open and it was stiff to remove so was slightly bent but you couldn't see it with naked eye, there was a rub on the piston where the valve had caught it sort of removed the coke coating but no damage but is of some concern now you mention it. I've tried starting it again tonight and am now wondering if it is a carb issue as I was fiddling with choke on and off and it fired and sort of run for a second or so then stopped it did this half a dozen times. I have a 2005 crf 250 that starts first kick so if I finish work early enough tomorrow will try that carb even just to eliminate it. I will let you know how it goes
  • User avatar
    JimDirt
    Posts: 4406
    Joined: Sat Nov 25, 2006 6:31 pm

    Re: Have I missed something?

    by JimDirt » Tue May 15, 2018 1:43 pm

    Did it sit for more than 1 month ?? , if so it could be the Pilot Jet is clogged , or that the gas (if its pump gas) has gone bad , these bikes don't like to run on old gas , so maybe if the timing is spot on , then drain the tank and carb and try it again , if it starts right up then that was it ....
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho
  • Harry1234
    Posts: 4
    Joined: Tue May 15, 2018 5:28 am

    Re: Have I missed something?

    by Harry1234 » Wed May 16, 2018 12:44 pm

    Removed carb tonight and found the hot start plug was out of the carb and that the plastic threads were shot, stripped carb and all jets were clear. Put the carb and my hot start plug on from my bike and it fired up after a couple of kicks and runs fine, starts good now so either the carb is shot or it needs a new hot start connector plug, would this plug stop it starting when not connected?
  • User avatar
    JimDirt
    Posts: 4406
    Joined: Sat Nov 25, 2006 6:31 pm

    Re: Have I missed something?

    by JimDirt » Thu May 17, 2018 7:35 am

    Yes it would cause a Lean Condition , as that is what it is designed to do , is lean the mixture when you crash or stall it when the engine is warm/hot so it will start easier ,, that is why you are told to use the "Hot Start" lever when you fall over and are needing to re-start the bike , if the engine is cold like when first trying to start it (which is your issue) then it will be too lean and difficult to start and it will also be running once started in a heightened lean condition as long as the plunger is pulled out , you are basically adding more air into the fuel mixture at all times , thus leaning the mixture at all times ....make sense ?? 8)

    They sell a metal Hot Start nut here , i have one on my bike , it eliminates the stripped plastic one that comes stock , its a common issue as the plastic is very soft and it does not take much to overtighten it and strip it ..... ;) https://www.crfsonly.com/catalog/produc ... ts_id/5100

    Replace that , and you should be back to riding .... \:D/
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho
  • Harry1234
    Posts: 4
    Joined: Tue May 15, 2018 5:28 am

    Re: Have I missed something?

    by Harry1234 » Thu May 17, 2018 1:16 pm

    That makes sense now, thanks for all you advice, much appreciated :D

Who is online

Users browsing this forum: No registered users and 2 guests