It's time . . . top end re-build thread '82 xs400-RS

[NewHavenMike]

New rings need a new hone always.

Those bores will need an oversize, the scoring looks bad and probably enough to skip the first oversize.

You might get away with it but thats up to you if you want to take the chance.

You already have the rings/pistons, you might want to look into getting a used jug. Parts salvagers tear down perfectly good engines and its not too hard to find a good original bore jug.

 

[dannyTheBoat]

I did notice the 1 bad score, but that measures below the stroke of the top compression ring. I'll scrutinize the others a bit more. That cylinder had good compression before the motor came apart so I'm optimistic. Thanks for the suggestion on getting new jugs. I think I'll look for some spare jugs while I put this back together and if it doesn't work out, doing a reassembly with new jugs shouldn't be too hard. The only oversize pistons and ring sets I'v been able to find run upwards of $300. That plus the bore job is kind of cost prohibitive.

I was able to get the rest of the head work done. The exhaust and intake are now ported and polished and the valves are all lapped. 3 of the valves are looking perfect but one of the exhaust valves looks to be too pitted for lapping to work. After a good amount of lapping there were still ridges on the sealing surface. Seat looks good so I'm gonna try a light cut on the lathe. If that fucks it up then I guess I'll have to pony up for a new one anyways. I have been sick so I was too lazy to take any good pictures during my last shop day. I'll update with some pictures next time I get my hands dirty.

After the valve fix I'm going to bead blast the top end and start painting. I think I might as well clean and paint the frame too.

EDIT: just found some jugs for $12 can't say no to that. Small gamble but the look good enough.