1. S

    Piston Play?

    Back again to hopefully ask one last question so here we go. In this video here (LINK), you can see the piston has a fair amount of side to side play. It does not have any up/down or angular movement. I know the piston wont move like this in the cylinder, but from previous questions I have asked...
  2. S

    XS400 Knock Noise

    1982 xs400s Heritage Alright so I made a thread about this a couple weeks ago and asked for some suggestions on what the noise could be. I finally got the top end fully taken apart as I have been busy since then. This is the video of the noise for reference. So while the pistons have been off...
  3. The Mighty Don Allan

    circlips over snaprings? or...

    Heyo, Im in the middle of a teardown, is there a reason that we shouldnt use snaprings instead of circlips to secure the wrist pins when setting up the pistons? As pictured below.. Thanks in advance!
  4. Vigeoman

    Piston head ruined. Need a completely new engine or just put on a new piston head?

    Hello everyone! My name is John and I am from Metro-Detroit. I bought an XS400 last year but finally got to working on it this summer. I just took apart the engine and found the left piston head completely destroyed. Everything else looks okay inside of the engine though. I am wondering if...
  5. O

    xs360 oversize pistons + piston rings

    Hello guys, can you please help me with searching for pintons and rings? Iam looking for set of pistons+rings for my xs360, but I can't find them.. minimum size, that I need is +0.25mm or bigger. It's possible to find them somewhere in USA? I was thinking about searching at ebay.de, but no...
  6. burr

    1981 XS400 Engine Build: A Story of Pictures, Videos, Beers & Tears

    Hey Everyone! After hijacking a few threads, I figured I'd start my own. I'm rebuilding my 1981 Yamaha XS400H (4R5 engine). It's my first bike. I'm pretty mechanically inclined but I've never worked on anything like this before. Here goes nothing… A Little Intro: Bought this guy for $600 CAD...
  7. U

    Can't figure out gas in oil

    I've read lots of posts on this. I have gotten my bike to the point where it is running great but after I ride a couple miles I get gas in the oil. It does not seem to be leaking into air filters and it's not the petcock leaking because I have installed an inline fuel cut off valve. I've read it...
  8. D

    Sudden loss of power during ride; subsiquent inability to start

    I was riding my 1977 xs400 and suddenly the was a small lurch and the engine died. When the electric starter is actuated, it sounds as though the starter motor is spinning without any load. The kick starter moves smoothly and oddly easily. I removed a spark plug and put a thumb over the opening...
  9. P

    Piston rings the problem?

    how can i see if my rings are bad? do i need to check the gap? really want to figure out if theyre bad before trying to track down a set...
  10. sgrudier

    New pistons and rings

    Anyone used a good kit for rebuilding their 400? I just did a compression test on my new find and the numbers are low. 40 dry and 90 to 110 with oil.