Pinned FZR250 - How to check & set valve timing (applies to IHX series engines, 2KR, 3LN, Zeal, etc)

Firstly you need to remove:

Fuel tank
Airbox
Carburetors
Radiator
Rubber engine cover
Spark plugs/leads
Stator cover
Valve cover
Misc. wiring
Removing the side engine mounts from the frame also aids with space/clearance when torquing up bolts etc, but is not absolutely necessary.





The first step is to rotate the stator until it lines up on the T mark like so:




When the stator is lined up with the T, check the timing dots on the camshafts and cam caps, on the left hand side of the engine (opposite end than the stator. Right hand side in photos) Both dots on each cam should line up more or less perfectly. Note that on the 3LN3 engine, the dots did line up perfectly. On the 3LN7 engine (which uses Zeal cams) they did not line up perfectly. You can see this in the photo below. Both are still the correct timing.



If the T on the stator is lined up, but you can't see the dots on the cams, rotate the stator 360 deg and then everything should line up. It wasn't lined up because that was TDC of the exhaust stroke for Cylinder 1.

If the timing has been done incorrectly previously then the dots on the camshafts will not line up with the dots on the camshaft caps, when the T on the stator is also aligned with the timing mark. In this situation, line up the timing marks on the crank/stator and then carefully remove the camshafts.

There should also be 6 links between the top of each camshaft sprocket at any time.



Once the timing is at TDC for Cyl 1 on the compression stroke (when all the timing marks line up), take out the cam chain tensioner. That will free the slack on the intake side.

After that, unbolt the centre 4 bolts on the cam caps and remove the little cover for the cam chain.



Then you should be able to lift the slack of the cam chain on the intake cam, and take the chain off the cam sprocket.

Then remove all the cam caps. Keep them in order. They are labelled I1 and I2, E1 and E2. I1 and E1 go on the left hand side of the engine (which is the right hand side in the photo), same side as the timing dots. Take out the little dowels as well.

Once the cams are out, that's it. You can rotate the crank freely.

For putting everything back together...

1) Position stator/crank on the T mark.





2) Insert exhaust cam. Ensure that the slack is taken out of the chain on the exhaust side. The cam has to be installed so that the timing dot is out by 1 tooth of the sprocket, in an anti-clockwise direction, otherwise once all the slack is taken out by the tensioner, the exhaust cam timing will be incorrect.


3) Lift cam chain and install intake cam. Ensure that 6 links are between the top of each camshaft sprocket. Ensure that there is no slack on the cam chain on the exhaust side. All the slack should be on the intake side where the cam chain tensioner goes.


4) Install the dowels and camshaft caps. Torque for the cam caps is 10NM. As the bolt torque pushes the cap and camshaft down, it will expose more slack in the cam chain. Ensure that the chain does not slip off the camshafts. Use zip ties if necessary.


5) Install the cam chain tensioner body. Ensure that the ratchet has been pushed all the way in (not extended). Install tensioner spring and bolts. Rotate the stator slightly so that the cam chain ratchet extends (you will hear it clicking)


6) Rotate crank/stator once until the timing mark lines up, and then do it once more (720 deg. total rotation). Ensure that there is no binding when rotating the crank.


7) Check camshaft timing marks once the T is aligned on the stator. In my case, the exhaust one was correct but the intake cam was out by 1 tooth anticlockwise. This is why you initially install the exhaust camshaft 1 tooth anticlockwise to compensate in advance. It is caused by the tensioner taking up the slack of the chain.


8) Repeat step 6. Rotate crank/stator 720 deg.


9) Check timing again. If the timing is still out out (most likely on the intake cam), align the T on the stator. Remove the cam chain tensioner, and then loosen the intake camshaft caps. Lift the cam chain off the intake cam, and rotate it as required. It's okay to do so as that's where all the chain slack is, so it's easy and won't harm anything.

10) Check the torque of the camshaft cap bolts. They should be set to 10NM and no more. Make sure to install the cam chain guide in the center. It sits on top of the camshaft caps.

 

That timing is fine, the 3LN7 motor is the same, they don't line up absolutely perfect.