New to the group so apologies if this subject has been discussed. I purchased a 2024 Kawasaki ZX-14R 40th anniversary last year. About 2 weeks after that a friend gave me his 2008 ZX-14 with only 850 miles on it. I wanted to change the original tires on the 08 to something more aggressive than stock so after some googling I came up with the Dunlop Sportmax Q5s. I got such great deal from my local bike shop I had them put them on the 08 and the 24, front and back. I love the way they handle and grip at higher speeds but the problem is I get fork shimmy between 40-45 mph, on both bikes. I thought is was the balance but had that rechecked. I put a steering damper on the 24 which made it better but its still there. I have not tried tightening anything beyond stock. Both bikes did not do this before the tire change. Any ideas?

I'd say it's definitely the tire so at least you know it can be solved. Any time I've heard of this, it's been tire cupping but that seems unlikely since the tires are new. If you used the tires for some time, it's possible they cupped. I've never had that issue and forget what causes it. Have a look at the front tire. If there's severe cupping, you might see the wavy edge to the outermost wear on the tread. It's also possible to have cupping that's not visible.

Are the weights OEM reused or tape-a-weights? Might try a 180° spin on the tire to the wheel and rebalance. For both to act this way is probably the weights.

All fail to work, might want to try the beads for a balance. My try is rise the tire off the ground, front axle thru the wheel (no spacers in the wheel) and spin it to see where the weights land on stop. Spacers removed is for leas drag thru the wheel seals.

So say after the first stop, set the wheel at 12 o'clock with the weight at the top and see if the wheel moves. You know the wheel is balanced if you set the wheel in any position and remains there. Any movement shows your forks shimmy.

I had cupping issues with every front tire from different manufacturers for the past 3 years on both my 2012 and 2023. This caused my front end to shimmy at moderate speeds, but as you've stated your tires are brand spanking new. I finally found the cause of why my front tires always cupped after about 1500 miles of use, and the solution was my front rebound settings. My settings were cranked up to 6-8 clicks from full hard and once I dialed it back to 3 clicks from full hard, and of course ensured to maintain proper tire pressure my last 2 front tires haven't cupped and I got full use out of them. Since both bikes are exhibiting this issue with the same brand tires, you've had them balanced and rechecked, I'd suggest tinkering with the front end compression/rebound to see if it helps.