checking NX250 valve clearances

[scrambler]

The valve clearance is measured with cold engine.
Remove the upper brackets of the cylinder head and remove the water cooler bolts. Pull the water cooler out of the frame holder, otherwise the head cover cannot be removed.



Unscrew the spark plug and the two caps of the alternator cover. Turn the crankshaft counterclockwise until the "T" mark (top dead center) is aligned with the mark on the alternator cover. Check whether all valves have play - otherwise keep turning until the “T” mark appears next time.



the valve clearances can than be measured. The valve play changes very little over time and gets smaller. At my Nixie I had to correct the valve play the first time at around 90.000km. Rattling or clacking noises have other reasons.



At this point you should check the timing chain. It could have skipped a few teeth or it could be too long. If the markings at top dead center are like this and the chain does not feel loose, everything is ok.

[Wout1980]

Thanks for the information...

[scrambler]

I also removed the cover to the chain.
I think the timing is still alright.

20220301_192446.jpg

Take a look at this thread. The piston must be at the upper dead top center to check the timing. On your pic it doesn't look like

[Staubteufelchen]

If the big cap of the alternator cover is stick, don't use brute force, this part is sensible and expensive (24,03€ before tax, this week in Germany). You can open the small cap and rotate the rear wheel, while the engine is in gear (Sparkplug removed of course) to find the T-mark.

[sandernx]

Hi,
Is there also an instruction thread in this forum on how to change the shims for the correct valve clearance ?
Best,
Sander

[scrambler]

Is there also an instruction thread in this forum on how to change the shims for the correct valve clearance ?

There are no instructions yet, simply because it is so rarely necessary. And because it's a bit tricky. I I'll see if I can slap something together in the next few days.

After you have noted the valve clearance for each valve you can remove the tensioner and the camshafts - the crankshaft must be at TDC (see above)



Deviating from the workshop manual, I proceed a little differently and only remove one camshaft at a time, it's easier that way. Because you can leave the cam chain on the opposite cam.



Then you pull out the cup tappets. The best way to do this is to use a magnet. Sometimes the tappets get stuck, then a cold spray helps.



With a magnet the shim is pulled out together with the cup plunger.



The thickness is printed - the writing is often no longer legible, so a measuring gauge should be available.

NX250 shim lettering.jpg

Note the thickness of the shim for each valve.

Now calculate the thickness of the new shim.

New shim = valve clearance measured - 0.23mm + old shim

for instance
valve clearance measured = 0,13mm
old shim = 1,8mm
new shim = 0,13 - 0,23 + 1,8 = 1,7mm

[sandernx]

Thank you for the explanation.
It says to remove the cam shaft holders. Are these just bolts ?

[scrambler]

aluminium bearing blocks (?) you still need the information for assembly ?

NX250 camshaft holder.jpg