Jump to content

WR250 Not Starting

Recommended Posts

Hi, I recently bought a 2002 WR250F. I knew it wasn't a great bike, but I couldn't pass the deal up. I've had a lot of trouble starting it recently. I had the carb rebuilt and jetted by the dealer, but that still did not fix the issue. The bike will start when rolled, but I can't get it to start kicking it. Does anyone have any advice on what I should do, or know what the problem is?

Share this post


Link to post
Share on other sites

Valves closed up.  Probably needs a top end with valve replacement... classic symptom is they will only bump start.  At that point its beyond the pail.  Plans....... piston and rings / gaskets / valves, seals / cut seats / oil pump gear rotor /  cam chain, sliders.  

Check crank small and big end while its down for excess play (mic'd) and main bearings.  Only say that because its 02 (15 yr old)

Share this post


Link to post
Share on other sites
On 6/12/2017 at 8:50 PM, ronbuell said:

Valves closed up.  Probably needs a top end with valve replacement... classic symptom is they will only bump start.  At that point its beyond the pail.  Plans....... piston and rings / gaskets / valves, seals / cut seats / oil pump gear rotor /  cam chain, sliders.  

Check crank small and big end while its down for excess play (mic'd) and main bearings.  Only say that because its 02 (15 yr old)

when you check the crank main bearings you have to split the case right?

Share this post


Link to post
Share on other sites

With the piston off the rod, hold the small end and rotate the crank slowly.  Usually I do it with the flywheel and cam chain removed so it will move without jerking (flywheel magnets with the coils don't let it move smoothly). LISTEN and FEEL for noise, roughness, check the rod for side play (movement side to side is OK as long as it doesn't lean over).  Movement of the whole crank assembly side to side in the bearings OK as well so long as its not over .050"-.060".  I think there's a spec in the book for it, but can't remember it off the top of my head.  Place the piston pin into the rod small end and check for any play in the small end.  My spec is if I find any play there, I replace the whole crank assembly.  A new crank will not have any piston pin play.  Any play can make the top end noisy.  Also I usually replace the piston and pin at teardown, but I go longer than 50 hrs which is rebuild time on a YZ/WR.  

Then I check for any up-down movement in the rod on the rod bearing.  It can move side to side as long as it doesn't lean over any.  Any knock or lean movement there means replace whole assembly.  Last, I check the small cam sprocket.  If the teeth are sharp and pointed, replace the whole crank assembly because you can't replace just the sprocket (aka Honda).  These are not negotiable in my mind because if the cam chain jumps time, the whole top end and head are trashed.  I replace both chain sliders at that time, replace or insect the oil pump gear rotor assembly for scaring (indicates metal has gone thru the oil system and internal passages need cleaned and all bearing in the case need inspected).  And I clean the magnets of the flywheel because metal will be attached to the magnets.  

If you replace the valves, you must have the seats cut so they will seal properly.  Pay for this about $100.  Remember this is a close tolerance engine so any play is not good.  If you do the whole job yourself, and replace the crank, valves, piston pin, oil pump, gaskets etc, expect to pay another $850 or so.  It should be essentially a new engine at that point.

Edited by ronbuell
  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×