Hi folks - just took the rocker cover (not head!) of my recently purchased Kawa ZX7R to check the valve clearances (after I managed to get the fairing off! Thanks guys!). Followed the Haines manual religiously and did a double check.Everything seems to be in clearance apart from three valves which seem on the tight side.
One of the intake valve clearances on cylinder #3 measured 0.16mm which makes it only 0.01mm out of clearance (intake valve clearance range according to manual is within 0.17mm to 0.25mm)
One of the exhaust valve clearances on cylinder #3 measured 0.19mm - which makes it 0.03mm out of clearance (exhaust valve clearance range is within 0.22mm to 0.31mm)
One of the intake valve clearances on cylinder #4 measured 0.13mm which makes it 0.04mm out of clearance.
natch I’m going to re-shim the tight valves and get them back into the specified clearance range.
Just wondering if the valves are seriously out of clearance (particularly the 0.04mm on intake cylinder #4) and if so are there any dodgy implications for the engine - e.g. sometime down the road (burnt valves and loss of compression). I have no bills for clearance checks for this bike - so I have no idea how long the valves have been in this state of clearance - current (indicated) mileage is 20k.
The bike ticks over ok and pulls strongly in every gear (got me up to the ton without even trying) - so performance wise it seems ok. Thanks in advance for any opinions. Kind regards, Sid
“So what happens if there is too little clearance ? Well, for one thing the valve loses most of it’s heat through the valve seat. If the valve doesn’t seat fully it will start to get hotter and hotter. Sooner or later the valve starts to melt or burn. Not good ! Now if the clearance is too much the valve train components will be hammered every time the valve opens. Again, not good but better then too hot.”
I would adjustn them, they need to be in the correct range. They’re not going to do any damage right now but the one that’s 0.04mm out could when the engine gets very hot tighten up. If you’ve already got the head off then it’s only an hours job to change them, as you’ve measured them pop the camhafts out and measure the shims already in there and then you’ll know what size shims to buy.If the head is off then you might want to clean up the ports and valves anyway, take them off and pop them into a drill and use lubricated emery cloth to clean the head then give them a very light lapping in to make sure you’re getting a good seal. If you do this you’ll need to remeasure the clearances.
The one that’s 0.13mm and should be between 0.17mm to 0.25mm needs to be done, it’s too tight and will cause a problem in the short term. When you add in a tired valve spring, maybe a slightly worn valve stem causing a little bit of stiction or lateral movement, all marginal things, it all adds up to a valve that’s possibly not going to close properly at high rpm.
Don’t think of it as only 0.04mm but try it’s less than half the maximum permitted size, almost 25% smaller than the minimum permitted size. I agree that 5% to 10% either side won’t make much difference but this is about 25% too small, big difference.
It’s almost 2 thou but that’s 25% of the minimum gap Seriously, I think it’s important. At 12k rpm or whatever it revs to things get critical very quickly. My busa engine only revs to just over 11k but I’ve had valve clearences set to be on the upper side of the range because the valves get hotter, especially the exhaust valves.As the head is off anyway it would be silly not to do these little jobs which can set the engine up for another 30K miles Little bits of maintenance like this all add up to an engine that runs better, smoother and probably for longer and also makes more power
Thanks so much for the advice and opinions posted above - it’s like I’ve got you guys in the garage with me - which makes fettling this thing a lot less of a scary experience! I’ve really enjoyed reading them - I find this kind of stuff really interesting - I guess that once I have reshimmed the bike and all the clearances are in order a compression check would tell me if there has been any damage to valves (particularly number 4 cylinder intake which is most out of clearance) and settle the issue once and for all? ;)Thanks again - drinks are on me!
Your valves let the engine breath. In with they fuel/air mix, out with the waste gasses. Too tight and the valves wont shut so you loose compression, performance and may, at worst, collide with the piston. To much gap and the valves dont open in time or far enough to let the enough fuel/air in, or get the spent gasses out.
So for the right performance you have to ensure that they are within tollerances. What you are talking about may be a small gap, but when you take it into consideration with the movement of the other parts involved in this process (position of pistons, valve opening and closing, firing etc) it can make quite a difference. Then to top it all it can affect temperatures of each cylinder, wont be drastic, but the worse they are the worse the effect on performance and engine lifetime.
So…Me personally would get them reshimmed.
Oh…being pedantic…I think you meant you took off the rocker cover
Agreed they should be reshimmed but my point is all this talk of valve damage etc is bol1ocks and is just putting the fear of god into the poor fella.:crying:There is no reason to think there is any damage to this engine which has a reputation for being able to go to the moon and back with very little bother.It’s easy to get too anal over the sake of 0.04mm when there are more important things to tend to;)
Cheers hkdloz! thanks for advice and yes I should have been clearer - the rocker cover is off - not the head! And thanks Chunks - your wise council is making me feel a bit more relaxed about it - I won’t go to sleep/wake up thinking that my cute 7R is nursing a set of burnt up ground in valves - which leads to visions of me having to spend more time/money on getting engine apart for re-grinding etc which would defeat the object of getting a cheap zx7r in the first place - I seriously don’t want to end up spending the same money as it would have cost to get a shiny low mileage one with a full service record - as this would leave me feeling like a total berk!:PI guess the proof that engine is healthy will be in the pudding - e.g. after re-shimming - the compression test?
You think it’s only 0.04mm but you forget that it is 25% smaller than what Kawasaki state is the lower limit, 25% ain’t small Chunky. Everybody seems to forget that a sports bike engine is a precision piece of engineering, it’s not like a car engine, most car engines will operate on very sloppy clearances and still run for 150k miles but when you’re getting 150bhp / litre or more from a little tiny engine that revs it’s nuts off, 2 or 3 thou in valve clearances is important.It’s not anal Chunky, it’s important. Might be anal on a low revving V twin that has dustbins for pistons but on an engine that lives above 8k rpm it’s very important. As I said originally, unlikely to be any damage now but if it’s not corrected it will lead to damage.
Doesn’t live up there though does it, like a Ninja does Mine makes peak power at 14,000 rpm and the midrange starts at 9k, 8.5k for a proper engine is just getting into the power band If yours is all over by 9500 then there are cars that rev higher than that :w00t: