engine question

  1. S

    '77 XS360 Backfiring above 5000 rpm + other issues

    EDIT: I think I found the issue, the new battery I installed is bad. For the life of me I cannot figure this out. Sorry for the long read but I feel like I should include everything I did, which is a lot. I recently replaced the coils on my Yamaha (1977 XS360) because the bike didn't really...
  2. Myke Nytemare

    What models (if any) have the same engine?

    Hello all, Ready to pull the trigger on an Xs400 that is not complete (lots of redone and new parts), but the engine is original and hasn't run in a while and when it didn't leaked and has physical (laydown) damage. Since I'm going to have some time putting the bike together I figured I could...
  3. G

    XS400 different models, and trying to find parts for yours

    Hello. Just joined the forum, great site. I'm hoping this thread will help me, and anyone else new to working on these engines (after current members have replied). My question is; what is the difference between the different xs400 models? Specifically, what parts can I order that will fit...
  4. R

    Engine knocking, wheel locking

    My 82 xs400 maxim just devoloped a new problem. It shifts fine/drives fine. But when in N,1st, 2nd range usually while parking it the wheel will lock up forward and reverse. Usually at this time I willl hear something knocking around in the engine. I did an oil change and didn't find any...
  5. K

    open to suggestions, need some advice

    I recently obtained an 81 xs400 with intent of customizing or modifying for a project. Upon initial inspection, engine turns over and seems to have compression. Carbs were said to be dirty and in need of cleaning (surprise..) But further inspection shows that I can only obtain the first three...
  6. cjxs

    What piston pin for xs400se?

    I'm looking for a pair of new piston pins as one of the two I have now is short and the other is bent. I tried looking at boats.net, but they don't have SE version on their site, so I wonder, which pins from which model would fit? Any ideas? Thank you!
  7. F

    spun a rod (not so much fun)

    Hello So i was trying to get my carbs equal and running good to gether when my engine came to a hault. Nothing loud just thought the motor stalled then i went to restart it wouldn't turn over. Tied up! Tore my motor down to realize i spun a rod bearing. It scored the crank and the rod...
  8. I

    Only runs for 15mins

    howdy, I'm very confused! For some reason my 79 Xs400 will only run for about 15min. Just enough time for my mechanic to ride it around the block a couple times come back and tell me it runs fine. Then when I get on it after a couple laps it dies whenever I put the clutch in. At first I...
  9. X

    80-82 pickup coil cover removal

    How do you get these things off? One side has a screw and the other has a flat plug or something at the end of a screw.
  10. P

    Camshaft alignment in Valve Cover

    Hello fellow 400XS riders! I have just finished my rebuild on my jugs and I have a question on alignment of the camshaft. In the manual it says straight up with the Camshaft centrifugal and Projection on the retaining bolt ( both marks lined up) with the LT mark on the alternator cover in...