Valve clearance - very loose, help
 

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.

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:
http://i63.tinypic.com/24xl6af.jpg

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

http://i64.tinypic.com/swwsih.jpg

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

The only thing I can add to this thread is the feeler gauge should be 'square' to the gap your trying to measure..Some gauges are angled to allow access and the gap is accurately measured when there is a slight drag/resistance on the gauge.
Apologies if the is 'teaching you how to suck eggs'..

Thanks chalk Two and nikroc,

I understand that the feeler gauge should be flat and taken at the narrowest bit. So, I don't think it is to blame, at this stage.

chalk Two, I tried your suggestion of holding down the rocker arm on the valve stem and tried to move the rocker arm. It did not seem to move independently of the rod at the back holding it, although there is a tiny bit of play. So, that has now been eliminated.

In order to show what I have done (not made some silly mistake like having the engine at incorrect stroke), I made a video and have uploaded it to vimeo at the following address so you can see the issue I am talking about.

https://vimeo.com/249521019

Thanks for all your suggestions so far.

Great video.....and I can only say Wow, that's a lot of 'float' (gap). I'm guessing you may have had a slightly rattly tick-over, at standstill, that disappeared as you rode it.

I know you will have seen both sets of marks on the CRANK. One is the 'I' mark and the other is the 'H' mark which are very close to each other. It is the 'I' mark you need to use whilst turning the crank bolt anti-clockwise. (it's easier to turn the crank with your 22mm ((from memory)) socket arrangement whilst the spark plug is out). The 'H' mark is a loose term for that marking but its definitely different from the singular 'I' beam shaped marking.

If both ex/valves were 0.7mm+ then that goes some way to stopping the theory that some kind of debris has found its way in to the valve seat closures, preventing the valves from closing fully (hence the big gap). Unlikely for both valves to be hit, separately, by debris and then result in having the exact same valve gaps. If one valve was correct and the other was 'wide', due to debris preventing closure, then you'd still have negligible rocker arm free play, unlike your video, as the correct valve would take up the 'slack' ...if that makes sense.

If it transpires that your ex/valve gaps were too large for some time, I would venture to suggest that there will be no detrimental damage caused, just, negligible, poor performance due to the valves not being open for the correct amount of time.

If that was an engine I had inherited, I would tune down those gaps to 0.18mm
and run the engine until it was warm (on the stand) and then do a compression test only to make sure all 4 valves, cylinder bore, piston and piston rings are sealing nicely and give a compression result of approx 90 p.s.i. (warm). This is just a health-check for the above components but mainly for your valves integrity (valve seats).

If you haven't got access to a compression tester (fits where the spark plug sits), I'd settle for adjusting valves to spec and riding the bike .

As for why both yours were at 0.7mm+ , especially if the lock nuts were tight, I can only guess an accidental setting has been made by someone in the past.

Compression device available on ebay..

Thanks Chalk Two.

I'm pretty sure that I had the "I" mark that comes shortly after the "H" mark on the crank, when turning anti-clockwise.

Thanks for your explanation. It doesn't seem like any foreign material has caused the issue as you mention.

Unfortunately, I do not have access to a compression tester. So, I may have to do the best and settle for it. The bike has been open for 2 days, having it's 'open heart surgery'. Time to put it all together. Thanks heaps for taking the time to answer my queries.