XJ650 Oil in exhaust after going through carb and checking valves

Hello,

First post here and am still learning to work on these old bikes, so bear with me.

Recently bought a 1981 XJ650 23k miles running good enough to commute. It had a bad stutter on idle when not warmed up, and the petcock was gummed up/had weak vacuum so I rode it around on RES. Decided to do my due diligence and clean out the carbs, I ordered a bowl gasket kit from Len and cleaned it all up. While I had everything off the bike I also did a valve clearance check, had one slightly tight intake and one slightly loose exhaust (0.0033 cyl 1 & 0.0085 cyl 2). I also did new spark plugs. The bike had some oil leaks thanks to PO bandaiding everything with gasket maker, but I threw on a new clutch cover gasket and fixed a few other leaks.

I did get the bike running again and managed to get rid of the stutter by putting the mixture screws at 3 1/2 turns, but after the engine warmed up it started smoking like crazy, and oil started dripping from the exhaust clamp area (4 into 1 exhaust installed by PO). I let it cool down and took off the slip on to find the inside wet with oil. I then took out the spark plugs and found 1&2 perfectly fine with a brown tint, cyl 3 still appeared clean, and 4 was only tan on one side, confirmed all plugs have spark. (Side note, PO also completely destroyed the spark plug threads and installed inserts wrong, so I replaced some of those and am still chasing compression leaks) The top of piston 3 looks wet, while the others dry. Also a noticeable oil leak from the head gasket around cyl 3.

I am going to get a compression tester next and check all 4 cyl but wanted to know if anyone else had any suggestions. I fear I’m going to have to do piston rings, or valve seals…and if it is worth the time/money. I also don’t understand what I could have done that caused the cylinder to all the sudden start getting oil into it.

 

Could be a couple of things causing the oil leak............of course pistons and/or rings or a damaged cylinder bore could be the issue, or somehow a valve stem seal got busted (this can happen if using the ""zip tie" method of holding a valve open during the shim clearance check procedure). Also, there are oil seals between the jugs and the head around the outermost 2 cylinder studs (forward and rear stud, outboard of the #4 cylinder) and oil could migrate from there over towards the #3 hole, although that would also require an injured head gasket.

The carb rebuild probably had nothing to do with the oil leak, just a coincidence of timing.

 

Could be stuck rings..... I would run it some more, I had a Honda CB650 with poor compression, and I didn't do anything but run it for a while and compression was good. However, to help things along I'd pour some injector cleaner (or some other snake oil with PEA in it) into the spark plug hole and let soak for a couple of days.

OTOH, the weepy head leak doesn't sound promising.... you could do a compression test, then a leakdown test.

 

I have chased what I thought to be a leaky head gasket only to realize that I messed up the valve cover gasket when re-installing. I would make sure valve cover gasket isn’t the real source.