So this is the third time that I tried to post this and so we'll see if it actually posts! I bought a 2000 XR400 in December and have been rebuilding it since then. I initially tore it down to the bare frame and then just started cleaning or replacing parts as necessary. I thnk its the pictures that have been causing problems so i'll try those again later. I didn't run into many major problems except for the typical swingarm bolt problem. I ended up cutting the bolt off and replacing the swingarm with an extra one I received with the bike. I took the engine into a machine shop to have the remainder of the bolt drilled out properly. I broke the engine apart just enough to replace the cam chain and then put the original piston and rings back in. I figure I could tear it apart later if need be. The carburetor seemed to be in decent shape but i decided since I had it out I would get an overhaul kit and replace the seals etc. I was finally able to get it all back together and after running it down the street a few times I got it to roar to life. Now I've got to get it running smoothly and properly and thats where I need some help. I've never tuned in a bike before so I don't really know a lot about it. 1. I put a UNI air filter in and so I think that I need to rejet the carb. It runs well enough at low RPMs but when I open it up going down the road (even when done slowly) it starts coughing and kind of sputtering. 2. It smokes like HELL!! Sometimes its not too bad but when I really start revving the engine I get a nice large white cloud forming behind me. I did not do any work to the cylinder or valves as they looked ok. I was unable to measure the cylinder because i do not have the tools for that. I am guessing that some new rings would be in order.