This is part 4 of the engine part of my Z650 restoration - you can find part 3 at Z650 Engine Rebuild Winter Project - #3: Engine 2 Onto Stand and Assessment
The last post was focused on getting engine number 2 onto a stand and giving it a quick look over. This time around I've spent an afternoon cleaning it (focusing on getting oil and debris off, not making it pretty and shiny or anything !) and doing some initial assessment to find out what is going on inside.
1. Jet Washing
I normally avoid jet washing motorcycles, there's just too much risk of water getting into the electrics or other places it shouldn't be. But in this case, the engine has been standing for years, and there are no real electrics attached.
The next 3 photos shows the worst part - before, covered in degreaser, and after. Inevitably it's where oil chain lube has mixed with dirt and built up over the years. While the end result is still not 100% clean, it's vastly better than it was, and enables me to see a lot more of what is going on.
I also jet washed around the front of the barrels. Slight head gasket weeping and leaks from the tacho drive are a constant problem with all the Z650 engines I've ever worked on. Unfortunately, this was the point where I discovered I really needed a lot more degreaser than I had available !
2. Turning the engine over
Before proceeding any further, I enlisted the help of my long-suffering wife to fix the jammed pivot pin on the engine stand. It turns out the problem was entirely my fault !
When I assembled the stand, I deliberately left everything loose knowing I'd probably need to wiggle things about to get the engine to sit nicely. I was mostly right, but it turns out the pivot pin was the one thing that needed to be screwed in just the right amount to allow the spring-loaded pin to work properly, and fully tightened up so the weight of the engine didn't pull it down at an angle. With me lifting the weight of the engine, my wife was able to pull the pin back so it could all be tightened properly.
Once that was done, I thought it was time to try turning the engine over. The result would have a big influence on how I'd proceed further. I did this by turning the crank using a 17mm spanner on the bolt at the right hand end of it. It turned really well ! It was smooth, but I could feel significant compression (a good thing !) If anything, there was a lot more compression than on engine 1.
At a later stage, I may put just enough oil in to keep the bearings safe and then try a more detailed compression test. It's possible to do it on these engines by hooking up the compression test gauge (it screws into the spark plug holes) and then giving it 20-30 rapid turns on the kickstarter. Multiply that by 4 times (one for each cylinder) and it's an impressive leg workout for the day !
Unless the compression is due to overwhelming numbers of dead spiders in the combustion chambers, I'm starting to think that this engine may only need the head replacing.....
3. Head Issues
The reason this engine was taken out of the bike in the first place was down to problems with the cylinder head. The critical one is a broken flange on the inlet manifold, shown below.
There is also a cam cover bolt with a broken thread, which I'd fixed decades ago with chemical metal and then forgotten about. It's functional, but ugly and means that bolt can't be torqued down fully.
4. Initial Internal Investigation
By this stage, I am becoming more and more convinced that the bottom end of the engine, may be good, as well as the barrels and pistons. This means it would be a case of replacing the cylinder head, and giving the cam cover a really good polish to make it nice and sparkly. I've got a spare cam cover (but it's got a crack in) and the one off engine 1, so it would be a case of working out which is nicest.
Before the light went for the day, I did three checks to find out more about what was going on inside the bottom end.
First I took off the breather cover, to see what was going on in the chamber beneath. There was a little bit of water (which I'm fairly sure got in when I was jet washing it), and a very small amount of debris, but it was basically clean.
Then I took out the oil drain plug. As expected, there was no oil in the engine. But it was a big relief that no water came out.
Then I took off the oil filter cover and oil filter, rotating the engine on the stand so I could look up into the chamber. The bolt was very tight, but came undone with the help of a longer socket wrench. There was oil in the filter, and I was impressed that it was quite clean and no sign of any water mixed in. The filter itself was a dirty and had picked up some debris, but I'm not too worried as that means it was doing it's job. The basket and spring beneath it were both clean and in very good condition. The chamber itself was oil-coated (a good thing) but very clean. I've just spotted in the photo what looks like a bit of swarf in the thread; I hadn't seen it when I was just looking, so I'll have to investigate that next time. It may be from where the bolt was over-tightened.
(
That's all for now ! Next time, I'm aiming to take the sump off to see what might be lurking inside, and may take the starter motor out so I can peer inside and see if there is any evidence of rust on the gearbox.