XT660Z
2011
~40 000km. Only owned the bike since 20K, so do not know if valves have been checked before.

I opened the tappets and tried to test the state of the valves. I find that the intake valves have their clearances quite OK. On the exhaust side, the top part (the Y-fork bit [edit: I understand from internet search it is called 'rocker arm']) is quite loose, and appears to be moving up and down as if it is loose at a hidden hinge (and moves up and down about 3 mm or so from my estimate [edit: Please see below, it was roughly 0.7mm]). To my inexperienced eyes, this does not seem right.

Has this been experienced by other people in the forum? What is the fix? Or it this what people mean when they say the valve clearance is really out?

Have you actually measured the clearance and/or tried to adjust it?

Hi nikroc,

I went out and measured the gap. Turns out I'd mis judged the max gap. When I put the feeler gauge in, I can fit a 0.7mm feeler in (which is still ~ 5 times the spec of 0.16-0.20 mm). See pic here.

The problem is, the whole upper part appears loose and moves up and down. It is moving enough that the top tips are currently resting on the valves. So, even if I turned the screws to create a gap, would it mean anything as the gap of 0.7mm will still be there due to the looseness? Here is a picture of the tips resting on the valves.

A bit baffled. Any thoughts would be greatly appreciated.

[edit: Some internet searching tells me that the rocker arm is expected to have some play. The play on the intake side was definitely much less compared to what I see on the exhaust side.]

The rocker arm (y-fork shape) is a single piece of metal. The two ends have screws that are adjustable to change the gap between the tip of the valve stem and the underside of the adjustable screw. The gap should be 0.16 to 0.20 mm.

The rocker arm can only be fealt moving in an up and down motion according to the gap measured when the piston is at TDC (index marks properly aligned on crank and camshafts).

Measuring should be done on a cold engine.

The schematic shows the rocker arm and the rod it rotates on.

Attached Images

	DSC_0065.jpg (196.1 KB, 21 views)
	4.jpg (30.0 KB, 18 views)

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Hi Chalk Two,

Thanks for your reply.

Currently, the tips on the rocker arm (parts 11 in the schematics you have attached) are resting on the top of the valve stem (tip of part 2 in your schematic, as seen in the below picture). There is a freeplay (up-down) motion of about 0.7mm in the rocker arm, which seemed rather excessive to me. My interpretation was that there was too much play of the rocker arm (as if part 9 is moving up and down on part 10 in your schematic).

My question was if this much play on the rocker arm was considered normal on the exhaust side (the play on the rocker arm on the intake side is much less) or if something is wrong here.

Picture of current state - the rocker arm tips resting on top of the valve stem:


And the current freeplay in the rocker arm of about 0.7mm (note the inserted feeler gauge on the right hand side):

There should be no free play between the rocker arm and the rod, part 10, except for a 'tolerance' fit that allows engine oil to exist between the mating surfaces.

As a rough test for play, I would consider closing down the adjustment screw by hand on to the top of the valve stem and then feel the rocker arm for play at the back of the rocker arm. It's a very basic test because to actually measure the internal diameter of the rocker arm you would need to remove the cam sprocket and the cam shaft retaining plate and then use a 6mm threaded slide hammer to extract the rocker arm shaft. The rocker arm then comes out of the the cylinder head. It's highly unlikely there would be a problem in the first place.

I think 0.7mm is over 3 times the maximum valve gap. I would re check your timing marks are correctly lined up and the piston is at TDC and then close those gaps to anywhere between 0.16 and 0.20mm, remembering that the gap may change as you tighten the lock nut on the gap screw due to the screws threads being 'pulled' by the lock nut.

For your gap to be 0.7, I would only guess the lock nut had backed off or a previous setting was accidentally set.

Apologies if I have, still, misunderstood your questions

__________________
I have a lot of growing up to do. I realized that the other day inside my fort.