Bouncing Chain after 14/49 Conversion

I've recently changed my sprocket configuration to 14/49 and a JT chain 112 link 520 X1R.
Went on a long ride this weekend to a bike festival and noticed the chain bouncing like crazy on load at certain speeds.  If I ease off it's ok but even if I don't load the engine (stay in higher gear) it does this.  Never seen a chain do this.
At the festival I was told the chain seems to have a lot of side play.  It's pretty much brand new.
Here's a video of it.
https://youtu.be/j0BznxVzfhI

Did you adjust chain slack using the old method (distance between peaks), or the new one (distance from swingarm)?

Erm, I did it as I always have by the amount of slack in the chain as per manual ie in the centre of the bottom part of the chain.

What is the correct chain length for 14/49 conversion

peterjfox69 wrote:

Erm, I did it as I always have by the amount of slack in the chain as per manual ie in the centre of the bottom part of the chain.

Yamaha released a new adjustment method, shown in this thread (midway down, Post # 10634).

112 links is fine for 14/49.

Thanks, I’ll give it a go.
Do you know the correct chain size for 14/49 configuration?

Does this chain look ok?
It’s only done about 200 miles .
Seems real loose in its sideways movement

https://youtu.be/h55oTxMRWRw

Just saw your note re chain size, thanks

That side-to-side play seems normal, have you been able to check the chain slack using the new method?

Worth considering that this issue may be related to your suspension oscillation problem that you reported in another thread; it could be that one malfunction is exciting the other.

johnkol wrote:

That side-to-side play seems normal, have you been able to check the chain slack using the new method?

Worth considering that this issue may be related to your suspension oscillation problem that you reported in another thread; it could be that one malfunction is exciting the other.

I'm going to have a look later, thanks for your time