[wilsonracing]

So I have an 06 crf250r, it doesn't start very well ( gotta kick it over about 20 times ) after everything I've read it seems like the valve need shimmed or checked. So I ordered a shim kit, got it torn down, and tried to check the clearance and I can not get the feeler gauges through between the cam and the valve buckets, not even a .008 so that makes me think its way to tight. So I pulled the cam and checked the shim sizes, they are 1.85 and up. Does anyone know what size it should be? Or how do I get the correct size? On another side note, when I set it to TDC the cam gear was not flush with the case. it was about 1 -- 1 1/2 higher on the back side of the case. So like 1 and 7 on the clock and not like 2 and 8 on the clock as the case is not level ( 3 and 9 ). Idk, maybe I'm looking intothat a bit to much??


To cover all the basic stuff, It has a new spark plug, fuel is new 89 octane, when it does run, it runs okish bogs at first from the take off, it also doesn't idle well, but when its going 2nd and 3rd and up in the rpm's its good. BUT if it stalls or dies, or you shut it off, forget starting it again..lol gotta kick it another 20 times or more first to get it started again.
Sorry, probably to much info. Thanks for reading and thank you for any help in advance

[JimDirt]

Well from your prior posts it still sounds like you have some carb issues , as for the valves , what you want to do is with the bike on a stand so its level , remove the large round plug on the clutch side , then remove the small one on the ignition side , and have the valve cover off , and pull the spark plug , now , crank the engine over by hand till you see the cam lobes point towards the rear around 2 o'clock position , as it is getting there go real slow with the kickstarter (by hand) and watch the cam gear marks , as soon as they are flush , stop , now look at the ignition cover hole/mark and look at the clutch side marks (it should be a arrow/triangle and a dot) , ALL 3 marks need to be aligned , to be at TDC , then and only then do you check the valve lash , sometimes regular car/automotive feeler gauges are to wide to work right in checking the lash , they make feeler gauges specifically for these bikes , they are really narrow .... with that said , check your lash and see what you get , there is no "use this shim" scenario , every bike is different , that is why they make shim kits .... there is some hope if you have a 185 and larger , as that means there is still some life left in the valves , for how long , is different for every bike , some may stay in spec 1 ride , others 40 rides , but once they start moving it is only a matter of time before they are toast

Now in one of your other posts you mentioned a head bolt (should be nut) missing , there are only 4 of them , so with one missing , there is a strong chance you also have a blown head gasket ....... once you get the valves in spec , I would do a compression check , you should be around 57 psi (it is supposed to be low due to the decompressor , otherwise it would be like trying to kick over a Harley)
, if it is less than that , then you could have valves not seating and/or a blown/leaking head gasket , since in your other post you mentioned a oil leak , it is a possibility the head gasket is also part of your hard starting issues , not to mention the carb issues , not to mention the valves being closed or close to it .........

To check the shim size there is a calculator here that might help you figure it out , but the quicker way I think is to just grab a smaller shim from the kit , go a couple sizes down (2) ,remove the timing chain tensioner , pull the tower bolts and tilt the assembly down so the chain has slack , put a wire or something (bungee cords work well) around the chain and pull the tower/cam out , tie the chain to the bars so it does not get slack in it and come off the crank gear , pull the buckets , and swap the shims , and put the tower back on and tighten it by hand (it is very low torque so don't hoof down on it , or you will strip it out) , , you do not need to put the chain back on at this time , then align the 2 slash marks flush with the head and make sure the lobes are facing the rear , then check the lash , if you can get a gauge in , check it , and see where you are at , if its at 4 or something , then pull the tower , and buckets and go 1 more size and see where you are at , get as close to 0.005 or 0.006 that you can , but no lower than 0.004 .. once done , if you do not have them , I can give you the torque specs to put everything back together ....

OR

Here is a link to the shim calculator https://www.crfsonly.com/calculators/cr ... m-calc.php

Report back with results

[wilsonracing]

Thank you for the info, I definitely will put it to use. To clear up the missing bolt , It was just the rocker cover bolt. Since then Ive gotten it replaced and no more leaks.
Back to the shims, It did have 180 and up in it. Am I thinking about this the right way?? The thicker the shim, the more the valve opens, Shouldn't that make the clearance ( less ) at the cup and cam lobe? So I need to go down in size of shims, 170 ish ?
So there is more clearance between the cup and cam lobe? That would mean the valve is opening less.

[JimDirt]

The Valve physically opens the same regardless , the lift on the cam lobe is what determines how far it opens , the shim size dictates how far the stem is in relation to the cup , which gives you your gap , as the valve is sucked up into the seat , because of the face cupping/dishing , so the valve moves closer in to the intake tract , so the shim puts the correct spacing back between the stem and the cam lobe by way of the cup into its needed location/lash , so basically when the valve is new , there is a thicker shim to take up the gap , yet still leave a gap so the valve does not hang open , as the face of the valve wears , it goes into the seat face , pushing the stem closer to the lobe , therefore needing a thinner shim to make up that difference that was lessened by the valve physically moving closer to the cup closing the gap from the cup to the lobe , which is why when you need a valve adjustment you use a thinner shim not a thicker one.......... Once the valve wear is at the no return point , you run out of thinner shim sizes and the valve is permanently zeroed out , the reason the shim size is limited , is so you don't continue to shim until the valve is so thin either the head breaks off or it is sucked into the intake tract , which would release the pressure on the spring retainers , then the spring pops off and your valve falls not so gently into the piston , then you have a bad day and need a entire bottom and top end ...... more or less ....

[Leardriver]

It sounds like you were one tooth off on the cam timing, which would explain the hard starting. Has it always been like that since you got it?

[wilsonracing]

Ok , that makes sense. I was just thinking of it backwards. So.... I got the shims in, and even did the decompression mod and it still wont start. Kick it over and over and over and nothing. I actually went back to the original shims that were in it when I got the bike, and it still doesn't start. I did find the decompression spring was broken, I since replaced it, and still no go. So should I just keep swapping out shims until I get it to start, or just have the head rebuilt with new valves? And if so, who does that without breaking the bank? Or can I but a new one complete?
Just getting tired of tearing it apart a million times and not riding it...Lol