The 04 YZ450F was going very well this weekend at Pembrey having survived my winter valve shimming exercise. Starting easier, though it had also been treated to a new plug, air filter, and replacement idle easy adjust air screw with intact o-ring. It had a start of season oil and filter change, but after the first day a check the next morning showed the level down to 'half' on the dip stick. I know the drill in the manual and I followed it, but I'm wondering if it may be like the Voxan 1000 I had. That was dry sump with a very tall narrow oil tank. You could not get an accurate level on that until it the bike was well and truly at operating temperature. I was told the oil temperature and expansion effect was such that just starting and idling for a couple of minutes wasn't enough. A bit of a pain not being able to be sure without taking it round the block, but that was the way it was except in the height of summer. At least it doesn't take much oil at all to top it up. No oil smoke when running and no obvious leaks. As far as I know it must be still on the original piston from when it was tuned by "Will Power" in 2004. It's not had a great number of hours use since then according to its history and certainly only 3 or 4 since we've had it, but I guess it may be time for a engine refresh. The 2011 KTM 350SXF also must produce more power than I expected or the YZ has lost some of the horses (58) it had on its fresh build dyno test but that was 10 years ago. We both were doing the same times within 10ths on each bike (though naturally my lad was 10 seconds quicker than me). That might be in part due to more optimal gearing on the 350 though given the 5 speed box. We were running 15/38 on the YZ, well in to the 90mph plus region by my calculations. It certainly felt like it on the long start straight approaching the hairpin. A pity there wasn't a speed trap. Perhaps a bit high geared, but on an unfamiliar course I always prefer to start over geared and not hit the rev limiter in top half way down the straight on the first practice run . While we were putting the spare rear wheel with ladder cut slick in once the weather dried and warmed up, we could have gone a tooth bigger but the lad preferred not to on a 'gear for bend sequence argument' and as he is the better rider I didn't argue. A dyno test on both might be informative.