Just bought my NC30 and I have to change the carb to head rubbers. Carbs are off now and all 4 slides were jammed shut and are now jammed open ! While they are off , I will give them a thorough clean and stripdown. Any pointers /recommendations. Wasn't going to go to the expense of ultrasonic cleaning , unless you guys think it's essential.

There's a few reasons why the slides might be sticking but it's most likely because the diaphrams have dried out and are not supple enough to move freely.

To remedy this take out the 4 slides and soak in some petrol overnight (this won't harm them). When you install them make sure they're put in properly and that the slide covers clamp them correctly to make a proper seal.

I've often heard that you should never let the diaphrams dry out (e.g. sit around for a long period in a bike not being used), it certainly doesn't do them good but they can usually be brought back to decent condition by soaking in petrol.