After my weekend post, where I finally made progress after what felt like being stuck for so long, I did a little more work this evening to keep up the momentum.
I kept my goals limited because I knew I only had an hour or so of light once I finished work for the day. The plan was to get the pistons off so I could get a really good look at them.
The photo below shows the pistons still in the engine. Because I knew number 3 was potentially the biggest problem, I turned the engine over so that 2 and 3 were at top dead centre. That made it easier to get at the side so I could remove the circlip (arrowed in the photo below).
Getting that first circlip out was pretty fiddly. It's basically a case of holding the piston steady with one hand, sliding a small screwdriver under it without damaging the alloy piston with the second hand, then flicking the circlip out and catching it with my third hand....
Notice that I've really packed the openings under each piston with lots of towel - the last thing I wanted was to have to try to fish a tiny flying circlip out from somewhere in the bottom end !
Each piston has two circlips holding the gudgeon pin in, one on each side. But you only have to take out one to remove the piston. Once the first circlip was out, I had the "knack" for it, and the other three came out really easily. I've ordered replacements off eBay; they are cheap, and an item that shouldn't be re-used unless you have no other option.
For all four pistons, I was massively happy that the gudgeon pins slid out smoothly, but with that nice bit of steady resistance that shows they were all still a perfect fit with no sign of damage.
The photo below shows the engine with all four pistons removed. The small ends look to be in pristine condition. The other good news is that the spanner holding up the cam chain is still there and I haven't lost the chain inside the engine !
The next photo shows the four pistons. Note that they are sitting on kitchen towel with the cylinder number written on in Sharpie so I don't get them mixed up. At this point, they've had a quick wipe, but nothing more. On 1, 2, and 4, the rings move freely although I'll still need to take them out to give the grooves a good clean. On problematic number 3, they are stuck. Why am I not surprised ?
Below are the pistons again after a bit more cleaning. The light wasn't as good, so they look darker, but actually they're cleaning up really well. The gudgeon pins have a little oil staining, but no rust.
I've imprisoned piston number 3 in a pot with about half an inch of WD-40 in the bottom. Tilted to the side it covers part of the piston rings. The plan is to try to free the rings up without the use of violence. I'll soak it in WD-40 for a couple of days, spray it with carb cleaner, stick it in the ultrasonic cleaner and if necessary use the heat gun on it. With any luck, all of that will dissolve the gunge sticking the rings in (it looks like coke and dried oil rather than rust or corrosion).
If not, well I've got spare pistons I could use, but I'd prefer to stick with a matching set if possible. I also would prefer not to have to replace just one set of piston rings, but to replace all four starts getting expensive !
Finally, a life hack for Kawasaki Z650's.
The photo below is my other spare engine, with the newly polished breather cover back on. It has a slot for an o-ring underneath, and it turns out that it's exactly the right size (90mm) for the old oil filter cover o-ring to drop into.
Because it's just there to pad the surfaces and prevent metal to metal contact, and doesn't have to hold oil in the bottom of the engine, it doesn't matter that it's an old o-ring. Recycling 1970's style !
