I had a wrist pin bearing explode on me during operation. It showered needles all over the engine. I found them on top of the piston (some still nailed into it), in the crank case, and even in the RV cover (caused total destruction of the brass gear). The engine would still turn over, but you could hear the death rattle/clack as it did so. The only needle bearings in the engine are in the wrist pin, and in the lower part of the connecting rod where it attaches to the crank.
Checking the wrist pin bearings shouldn't be too hard, simply unbolt the head from the cylinder jugs and remove. It's sealed with rubber O-rings which you might actually be able to reuse. Once the head is off, grab the PTO flywheel and rotate it back-forth. If the pistons have a lot of play, you're probably looking at wrist pin bearing failure (and you're lucky as hell the whole thing didn't blow up like mine). To check the bottom bearings ,you have to pull off the cylinders, which is also easy and requires the removal of 4 more bolts (per cylinder, 8 total). The cylinders just come off the crankcase. The cylinders will have water lines attached to the back. Not sure if you can see that in a Speedster, but it's hard to get to on a jet ski. Once you pull the cylinders off, the piston and connecting rods will be exposed for inspection. Top-end gasket kits are pretty cheap, and if you're already this far into it, I'd go ahead and order a set of wrist pin bearings even if they do look good.