timing ??? kx250f

just put in new piston and rings buttoned it up after first revolution of kick starter it stops when intake lobe presses down on bucket - seems like valves are hitting piston but i've redone it 3 times each time checking timing marks and alignment of cam markings - what am i doing wrong????

Are you sure your not 180* out of TDC or at BDC.You can spin the flywheel around and line up the mark and be 180* out.Try putting a pencil in the plug hole to make sure your at TDC.Also did you put the cam chain tensioner in correct.Just a few thoughts.:thumbsup:

Are you sure your not 180* out of TDC or at BDC.You can spin the flywheel around and line up the mark and be 180* out.Try putting a pencil in the plug hole to make sure your at TDC.Also did you put the cam chain tensioner in correct.Just a few thoughts.:thumbsup:

I did it three times, the first two with a straw in the plug hole, aligned flywheel marking per manual and straw indicated piston was about 3/4 of the way to the top but not at its highest point. I should note the flywheel has two marks on it when aligned its either 3/4 up or down at the bottom which is where i did it the third time.

Can you count 28 cam chain pins from cam gear mark to cam gear mark?You did put tension on the tensioner right.Are you sure the cam chain is still on the crank gear?

Pistons in with the arrow pointing in the right direction?

28 pins exactly as pictured in manual...

I can look tomorrow at chain on crankshaft, but it does rotate the piston so i assume its on there.

Pistons in with the arrow pointing in the right direction?

dot is at the exhaust side per manual.

Can you count 28 cam chain pins from cam gear mark to cam gear mark?You did put tension on the tensioner right.Are you sure the cam chain is still on the crank gear?

tensioner can only go in two ways either slightly facing up or slightly facing down, facing up per manual...

Thats all I can think of.:thumbsup:

thanks, i'll try again in the morning, will re-check all the items you brought up.

I was almost sure I did it right the first time, but I was 180 off. Make sure.. haha. That's likely it.

The engine timing procedure isn't too difficult on these engines. If you're as far off as you say, I'd start from scratch. As far out as you describe, if you removed the flywheel for inspection purposes, you may have “pushed” the flywheel key out of the keyway on the crankshaft allowing the flywheel to not be in alignment with the crankshaft. If this is the case, you’ll want to locate that flywheel key as it can do some severe damage to the stator if it gets between the flywheel and the stator! This would throw off all of your timing marks, so I’d probably verify this first. Next, I'd start by removing the cam chain tensioner and then the camshafts from the head. Now you can rotate the engine without the worry of piston/valve interference. As people have posted here, make sure that the piston is at top dead center by removing the spark plug and inserting a long rod/straw to get a visual of the piston location/movement.

If you're not sure whether the cam chain is on the crankshaft sprocket, remove the flywheel and verify. If you remove or loosen the cam chain guide below the crankshaft to install the chain, make sure to use red Loctite when reinstalling the cam chain guide bolt! Once the cam chain is on the crankshaft sprocket, verify that the piston is at TDC by rotating the crankshaft by pulling back and forth on the cam chain. At this time, use a zip tie or some safety wire to "hold the cam chain". I usually wrap the safety wire to the upper frame spar.

Now you can reinstall the flywheel and the ignition cover. Make sure that both plugs have been removed from the ignition cover. The larger one is for rotating the crankshaft and the smaller plug is for viewing the timing marks on the flywheel. There are two marks on the flywheel, one for ignition timing and the other for mechanical timing. So, as you rotate the crankshaft in a counterclockwise direction, the first mark on the flywheel that aligns with the reference marks on the ignition cover is for ignition timing. You want to use the second mark for camshaft to crankshaft timing. Since these marks can sometimes be difficult to see, I use a paint marker or Sharpie to highlight the marks on the flywheel. Once this second mark is in alignment with the inspection window, verify that the piston is at TDC and install the exhaust cam so the "lower" timing dot aligns with the top of the head surface towards the front. Next, install the intake cam so the "lower" dot aligns with the top of the head surface towards the rear. As you have mentioned, count the pins of the timing chain and verify that there are 28 pins from “dot to dot”. This is illustrated well in the Service Manual.

It's now time to install the camshaft caps. Always verify that all of the dowel pins are secure in the cylinder head when installing these caps. If a dowel pin is in the cam cap, remove it and install it in the head, as I've seen these "fall out" when trying to install the caps with these dowel pins still in the caps. There are two dowel pins in each cam cap. Make sure to put the cam cap bolts in the correct locations. A general rule of thumb is that there should be about 2 ½ times the diameter of the bolt exposed before a bolt begins to thread into its bore. (Generally speaking, a 6mm bolt should have about 15mm of thread engagement.) I generally install the positioning rings on the bearings for the camshaft bearings/cam caps. Also, ALWAYS torque the cam cap bolts! The torque spec for these bolts is 87 in-lb. Another warning: cam caps cannot be purchased separately for Kawasaki’s motocross bikes! To get the caps, you have to purchase a head assembly, so be careful when installing these caps and verify that they are “seated” against the head before tightening!

Do not be tempted to turn the engine over yet, as the chain can “jump” without the cam chain tensioner installed. Fortunately, Kawasaki uses a self adjusting tensioned in their KX models. Press in on the cam chain tensioner’s lock and press the adjusting bar until it fully seats. Now install the cam chain tensioner in to the cylinder. Again, as you noted, it is directional! Once the mounting bolts have been tightened, install the center adjusting bolt, pin, and spring. You should hear the adjuster “ratchet” into the correct tension. Now, you can rotate the engine in a counterclockwise direction to verify that the cam timing is correct. I usually rotate the engine through a couple of revolutions before checking the timing marks and verifying the cam chain pin count. Again, the pin count for the KX250F is 28 pins. Once you’ve verified the timing mark on the flywheel and the camshafts “dot” locations, verify the “pin count” as well for the timing chain. If all looks good, you’re ready to “zip it up” and go riding!

Good luck, and I hope this helps!

Also....make sure you are on the correct marking on the flywheel when you start this.....there is more than one marking there

OK 4th time and still the same I give up parting ooout bike the the other 8 thumpers-I've had it back to 2 strokes-!!!

just kidding, apparently I was using the wrong mark. Buttoned her up and she fired right up, however now it has a bog when you give it gas-fires up with choke on, sounds fine, push choke off and give it throttle stalls, starts without choke and idles but give it throttle and bogs????

I wouldn't think its an accelerator pump issue as the jetting has been fine since JDjetting kit when we first got it and we didn't have this issue prior to opening her up.

Could Timing be off ever so slightly??

Your thoughts and THANKS for all the replies-!!

I have same problems on a 06 KTM 250sxf but not as sever as this one.

It's possible you could be one tooth off.Also if the bike has been sitting for awhile during your engine work the pilot jet could have got gummed up.clean it.

I'm going with the one tooth off, its only been a week since it was last started. breakin her down now will let you know in a little while.

OK here is the situation, re-set the timing, there are 3 marks on the flywheel, 2 are about 180 deg apart and then the third mark is just past the second mark. Thats the mark I used, straw in plug hole indicated it was at the top of the stroke. everything seems to line up per the manual, but I still have the bog and stall if you try to give it any throttle???

Ideas anyone-!!!

OK, here is the new situation, my son says clean the carb its got water in it from when i washed it the other day-!!

dropped the bowl, sure as sh#t water in there, cleaned her out, fired up beautifully-!!!

I would like to thank all for your insights and assistance and hope I can return the favor in time. Thanks again-!!!!

Glad we could be of help & it worked out.Out to the dez for the weekend,catch ya later.


I rebuilt my motor once. The problem that I had was that the book said when the two dash marks are in the sight, than the bike is at tdc. The book showed the lobes of the cams facing outward (apprx 9 and 3 oclock) but when my two dash marks were in the sight, the lobes were facing inward. So i just figured i was looking at the book wrong. After messing with it for about a month i gave up. I smacked a valve with the piston and bent it (its now at a show being worked on).

How do i get it at tdc with the lobes facing outward? If i was now on the right stroke..then how do i get on the correct stroke, and furthermore, which stroke is it?!

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