[Notuagn]

I bought my first motorcycle which is a 2006 CRF450X. When I bought it I was able to ride it home. The next day I tried to start it and neither the electric start or kick start would not start it. As much as I tried it would not start. I don't know why it would start and run one day and not start the next day. I researched what the problem could possibly be and the only thing I could find was that the shims need to be checked. The person who sold me the bike said they valves were stainless steel and they would not need to be shimmed. I decided to take my limited mechanical skills and check the shims. I got the motor to top dead center. When I checked the clearance it showed both exhaust valves at .13 mm and .15 mm. Both intake valves were 0. I could not fit the smallest shim in to check both valves. My guess is that this is not a shim problem based on the stainless steel valves and both intake valves at 0. It may possibly be that the engine was not top dead center also but I followed the steps of aligning all three arrows. I am at a dead end I don't know what to look at. The intake valve springs moved up and down just a little but I don't know if that is normal. I don't know if it is a carb problem. . Any help would be appreciated. Thank you

[JimDirt]

Welcome to the site !!

To check the valves correctly , you need to make sure of 3 things , you are top dead center on the Compression Stroke , that the 3 timing marks are ALL aligned at the same time , and that the cam lobes are facing 2 O clock towards the rear of the head

1st timing mark is on the cam sprocket , there are 2 slash marks , they need to be level with the head , at this point the cam lobes will be facing the rear of the engine around 2 O clock position ..... When that is aligned , there is a small round plug on the ignition cover (Allen Wrench) inside you will see a slash mark and there should be a line on the flywheel that is aligned with it ..... then on the Clutch side , there is a large round plug (Allen Wrench) right behind the water pump , inside it is a triangle mark and a dot/circle on the gear ....those need to be aligned .... when ALL 3 of those marks are aligned and only then , do you check the valve lash , it should be 0.006 +/- 0.001 for the Intake , and 0.011 +/- 0.001 on the Exhaust side ..... if all marks are not aligned , then either it is a tooth or more off on the cam gear , or possibly the timing chain is stretched (if it was not replaced) , also on the 06 , there is a manual decompressor for starting , it is the finger on the right exhaust valve that has a nut and set screw , when checking the lash you need to check it as well , the clearance is 0.014 while the feeler gauge is also in the exhaust stem , as shown in the 2nd picture





This is the Flywheel Mark to make sure you are at TDC (the picture is for a 02 450R but the marks are the same)

[Notuagn]

Thank you for your reply JimDirt.

I didn't check the De-compressor so I can put it back together and check that. I was told over and over that stainless steel valves don't need to be shimmed and honestly I don't know if that is true. I made sure I followed your suggestions on aligning the three marks to make sure it was top dead center. The cams are pointing to the rear of the bike a little up. My biggest concerns are two things:

If I was unable to put a feeler gauge in the two intake valves because they were so tight is that common or does that indicate that it may actually not be top dead center?

When you say manual decompressor what does that mean? Am I not starting the bike correctly?

Thank you for your help!

[JimDirt]

If you have a wide feeler gauge it may be that it is binding , a narrow feeler works best , IF all the marks are aligned and you are positive you are set in the right places , then yes there should be clearance

As far as Stainless goes , the longevity is very good .... for example , I put Stainless in my 06 in 06 , I have not had to adjust the valves since ..... with that said , there are a few factors that can alter that ...... (1) if the air filter is not sealing and the bike was ridden in dusty conditions and dirt got past the filter (usually the reason the Intakes are replaced in the first place unless the bike had tons of hours on it) which is what wears on the valve seat and valve face , cupping it and causing them to zero out ....... (2) If the valves were not adjusted correctly in the first place , then they would be tight and that will cause starting issues ............

There is one other thing .... but ..... if the valves have zero lash , then it is a mute point ...... Starting Procedure : .... When starting the bike when cold (the engine cold , not necessarily the outside temperature) , then you pull the choke (make sure the fuel is turned on and that there is FRESH gas in the bike , they do not like gas older than 2 months especially if it has Ethanol in it) ... Then twist the throttle 5-6 full twists , then hit the button , if the engine turns over real slow or sounds like it is really struggling , then revert back to valves , otherwise it should start right up , or at least attempt to , if it does not start but tried to , then twist the throttle a few more times (up to 6) , and try again , it should start right up ....... when the bike is warmed up , you should just need to hit the button and it should start right up without any throttle input ......

The Decompressor is a arm attached to the counterweight that allows it to work independently from the Exhaust Rocker Arm when the valves are open/closed , when the lash is set , the decompressor opens the valve slightly at start up , and lowers the compression to make the bike start easier , the arm is mechanically adjusted to get the correct lash , the other type of decompressor is actuated by a pin in the center of the cam that is pushed out holding the valve open , when the engine is cranked over , it is turning slower , and that actuates the Decompressor , yours is the arm type as shown in the pictures

[Notuagn]

Thanks JimDirt. I think I won't change the shims and put it back together. I think that the intake valves not having any clearance is a red light and I shouldn't make any changes. I would feel better putting it back together and starting over.

Thank You

[Back2-2]

If your intake valves are at zero you probably were lied to about the valves from the previous owner. It sounds from your description that you were at TDC so If they are in fact a zero you need to address that before anything else.

Someone on the site use to have term for shimming and selling. That sure sounds like what you got.