Piano World Home Page Forums Our Most Popular Forums Piano Forum Brand new Kawai K500 Stickyish Keys?

I am not that knowledgeable with pianos. So if I happened to use some technical terms, I am merely trying to describe the situation and might be using the terminology incorrectly.

I recently acquired a brand new Kawai K500 produced in 2021 for my son. During his practice I noticed some notes he played were weaker than others and he weren't doing anything different for the "weaker" notes he was playing. I suspected it has something to do with piano. After 20 minutes at the piano playing, I think I nailed down the issue.

If I press a key down, it will pay the note normally with normal dynamics; ie if I press harder the note is louder and if I press lighter the note is weaker. However, if I let the key go up a little bit slower or let my finger ride the key up (please don't focus on whether I should do that or not, I am just trying to focus on to reproduce the issue), the next time I hit the key, the key will play the note much weaker, the key also feels lighter when I hit it, It also does not have any dynamics (ie I can hit it as hard as I can, the piano will play the note the same way and very weak). It seems parts of the key (the Jack?) did not fully reset (I am not a technician, If what I just said is ridiculous please ignore it). This issue seems to be more prominent on the notes on Base Clef. It also doesn't matter if I have hit other keys or play next day, that particular key will play the "next time" weak until I hit it again and let it jump back up with full speed. I managed to record the issue:
In the video I exaggerated how slow the key needs to go up to cause the weaker note.

I understand the action for upright is different from grand piano. I understand for most uprights if I don't let the key go up completely, I can't play that same key again. But... was what I described normal for all uprights or for a Kawai? If you are a dealer, technician or have a lot of experience in japanese uprights. could you please comment on this?

How long have you had the piano? If very recent, it may still be acclimating to your house (humidity levels, etc).
Has it had it's first after-sale tuning/service?
FWIW, Kawai has a pretty good reputation for satisfying customers, and resolving QA issues.

Yea, the jack is not resetting.

This may be due to the change in humidity between its original place and your home. Or it could just be poorly prepped, or unprepped, maybe they plan on doing regulation during your in home tuning, don't know.

In the mean time before you get a technician to do regulation. What you can do is tape a 1mm shim to the bottom of the hammer rest rail, just little sliver of cardboard (IN 3 PLACES), and it should be good to go for now. Tape it onto the rail, don't tape onto the felt. If it still does it, add another 0.5mm

The Yellow arrow points to the rail, the big tube under the hammer

The Yellow circle is where you shim it, The blue arrow is where it's not resetting.


The technician can fix this, it's a trivial problem, mind at ease. This usually happens when the humidity goes UP.

Becareful taking the front panel off if you're working on it, you don't want to chip the veneer.

That is not necessarily the problem. Since you have a new piano, have the dealer send a technician to fix it, rather than doing anything suggested on the internet.

That absolutely is the only way to fix it temporarily unless he wants to get in there on his own with a tiny wrench to turn the capstans.

It may not be the cause of the problem, but it's the only intermediate fix any piano novice can do.

Taping some cardboard to the bottom of the rest rail. My advice is completely scientifically sound.

Words of wisdom from a piano tech. And remember, your piano is under warranty.

The OP should just let the dealer's tech deal with it.

He could but this isn't rocket science, my tip will work in the mean time until the technician comes out. We have a serious case of learned helplessness if we can't deal with a little tape and cardboard.

I want to thank who have replied. If you have your 2c, please keep it coming.

Based on what I heard I guess this is not "normal" for uprights to behave this way. I have no experience with uprights. I didn't know if this is expected quirk for uprights or Kawai uprights in general. for example, came from grand pianos, one would not expected the keys cannot be pressed again until it is fully reset. I was also curious whether this is a Kawai problem since its action is carbon fiber (vs wood. but then yamaha uses ABS jack too in their actions). Frankly I just love to hear all your different opinions. I can learn so much from these discussions.

iliveinope, watch this video, it explains the whole system. and where it talks about the JACK is the problem you have.



This is not unique to kawai action. The plastic parts in theory should make this problem less likely, but as there is still alot of wood all over the place, the action is not immune to humidity changes.

The upright can not reset on release as quickly / as low as on a grand action, but it should still be able to reset slightly before full release. Overall, a properly regulated upright can still give you ~7-8 repetition per second, which is more than enough for any real repertoire. They will be harder to play than grand, because you do have to time slightly higher/longer for the jack to reset.

I do agree with both of you on this one. Yes I am not qualified to completely fix this issue nor that I want to. But at the same time knowing what's wrong with it, will help me to appreciate the engineering behind it more. I am not worried about the dealer or Kawai wouldn't take care this issue. But they probably won't explain it to me like you all have done. =)

Make sure you show your stance of dominance and know your stuff or the tech might think you're easy prey and rip you off. Not all techs are like that, but it's a big world and we've got the same issue with car repair shops.

We got a pandemic, people are desperate, it's getting real gangster out there in the real world.

I saw this one. that's how I kinda formed my theory in my original post. where I wasn't sure is that since Kawai has carbon fiber action, can it be "different" from actions constructed with wood? I just don't know... in addition since Kawai's action is carbon fiber, in theory, humidity should have minimum affect on it (humidity is low where I am). I wasn't sure it is common issue with upright pianos or I just got a "crappy" copy or Kawai is just bad at QA.

Pianos have to be prepped at their destination, because felt landing pads, and wood even with the use of carbon fiber are not immune to humidity changes, only "Less so" than a fully wooden action. A full regulation is time consuming, if the dealer is trying to cheap out on labor, he could be skimping on the preparation of his fleet.

But it's also equally possible that the humidity is just very different from where the piano came from, not necessarily stored at the dealership either, they could've shipped it in from somewhere else.

I don't think there's such a thing as a bum K500, these are expensive parts. You definitely didn't get a copy.

When I said copy I didn’t mean it is a counterfeit.

Do not rely on a second-hand diagnosis from someone whose expertise comes from watching a YouTube video.

What is the humidity of the room? You can get an inexpensive hygrometer if you don't have one. Piano's do best from around 45% to 50% relative humidity.

As others noted, it seems a regulation problem caused by change of environment. I have a K300 and had the exact same problem as your describe when it was new ~ 1 year ago. It was, as EinLudov suggested, linked to humidity going up. Above 55% RH would be problematic. The dealer's technician fixed it for free. In my case, it turned out that some felt in the whippen was slightly too tight around a metal axis pin. As humidity increases, the felt expands a bit and then the axis becomes too tight. The technician changed the pins on two keys to slightly smaller ones. A less dramatic form of the same problem later recurred on two different keys. This was solved by the technician by applying some (water-repelling?) fluid.

Really, no. 'Stance of dominance' should have no part of your relationship with your technician or, preferably, anyone.