I bought a 2011 Raga 300 that had above-average engine vibration and engine noise. The bike worked fine but not as sweet as my 2010 TXT-motor, aluminum center cases 280 Econo. The vibration is hard to describe, so here's a very short video of the noise when running, and also killing the motor - in slow motion. Click on the photo thumbnail to go to the video. You'll hear the above-normal vibration when revved. Pay close attention to the T-T-T-T noise in time with compression when the engine shuts off. The T-T-T-T noise is consistent with excessive radial play in a main bearing, which I detail below. Some added vibration may be coming from this crank crank being sub optimally balanced (I later found the crank and flywheel are very well balanced). I'll concentrate on what I know is not as it should be... one of the two main bearings. Tearing into the bottom end I discovered the right main bearing to be undamaged, smooth rolling, but having excessive lateral play (and thus some radial play). In contrast, the same part, the left main bearing is much tighter. I could not get no more than a very tiny bit of visual lateral play out of it, whereas a video following will show lots of lateral play from the right bearing. (Update on this. I found the lateral play to be normal - see a later post. I found some bearing race wear from grit, and as a result am replacing both bearings to be sure). There are many custom features of the Pro engine design. Fascinating and admirable stuff to a mechanical engineer! The transmission is a wonder of integrated design. Four gear sets for six speeds and things like the shift drum rotates around the shift shaft. This is a super compact design! The main bearing design is custom to GasGas and also smart. The design lubricates both bearings, which ar ethe same bearing, both sides, from the transmission lubricant, not from the premix. This protects the main bearings from anything that may pass through the air filter on bikes whose bearings are lubricated via the fuel. A custom feature of the GasGas main bearings is an extended races on one side of the balls for the pressure seals, which run on the inner race and face inward toward the crank. This allows sealing on the inside without a larger seal pressed over the top of the bearing and into the cases. The left or magneto-side bearing has a conventional additional outer oil seal pressed into the case. Left bearing lubrication is trapped between the seals and lubrication is supplied from two holes drilled to the transmission cavity. There's an oil splash trap on the upper hole. When the gears are turning there is a flow from the upper hole and back to the lower hole. Otherwise oil just stands in the bearing cavity. The right bearing has only the one integrated pressure seal and the bearing balls are open toward the outside, lubricated by the transmission oil from the primary cavity (the clutch side). The Pro engine is super easy to disassemble as there are no hard press fits anywhere. The bearings have an O-rings in the inner race to seal on the crank, and an o-ring in the case to seal the outer race from the cases. I didn't have to beat or press the crank out of the cases... it just slipped out under a little pressure. Nice! Here are a couple of pix of the main bearing in the right center case, then the left center case: Here is the left main bearing from the inside: The feel test for main bearings is simple. You grab the inner race and force lateral play. The integrated pressure seal impinging on the inner race damps out movement a bit, but it's pretty obvious when you have a sloppy bearing. The identical bearing on the left was very tight feeling. Here is a video of the lateral play in the right main bearing: (update: I was wrong about this. When I received my new bearing, and examined all the bearings with no seals, I found the later play or tilt to be .011"-.013" on all the bearings. The radial play was very hard to measure, but it was near zero for all).