Yesterday I purchased a 2000 Honda 400ex from PA. I ride predominantly trails and hill climbs. All stock engine except for a replaced timing chain. Has some aftermarket bolt-on's and a white brothers E-series slip on. Has a fairly new rear carrier with a grommet installed for greasing. Overall I thought it was in pretty good shape for most 400's i found on craigslist. The bike has supposedly sat for about two years and could use a fresh tank of gas which I will be draining today and running 93 from here on out. I noticed a slight amount of smoke on occasion after a high rev in the garage and then also when i was using 2nd to keep my speed down(obviously at a decently high rev) while riding down a decently steep hill. I changed the oil before this to the pn4 10w40 but on the next oil change I think I will switch to mobil 1 15w50 to see if that helps. I feel like my valves may need adjusted but I'm not totally sure, If anyone has any wisdom to share or be able to direct me to helpful links I would very much appreciate it.In my opinion the engine seems to get fairly hot quickly which I would attribute to the oil and 80 degree temps( my thought). I plan on riding this weekend and then changing the oil again afterwards to help clean out the previous owners oil which was black and fairly broken down. I drained the gas however and removed the filter box to spray carb cleaner into the carb to try and help clean the carb a little without tearing it apart. I also put some Lucas fuel treatment in the gas to also help with cleaning the fuel system. When I test rode the bike I didn't tighten the air intake to the carb or put the air box lid on but did put the air filter on. When trying to go up the driveway it bogged down multiple time in multiple gears, would the filter box lid not being on cause that? It may have also had the fuel petcock on reserve. I can't recall though.