Z650 Engine Rebuild Winter Project - #1: Initial Assessment

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I've been working on restoring my old Z650, which has turned into a much bigger project than I originally expected. But with no indoor workshop, rain and "real life" commitments are making it difficult to find complete days when I can work on the bike.

So I'm setting myself a winter project which I can do under cover in the dry. I have two spare engines for the bike, as well as a spare head, pistons and barrels. They're all in poor condition and have various problems or faults.

I'm going to start working through them, seeing how far I can get restoring them without spending any major cash. It is possible that I will come across problems that are a complete show-stopper, or I may be able to get one working engine out of it. But if nothing else, I find working on engines quite therapeutic compared to messing around with fuel systems and electrics !

Although I haven't got a workshop, I do have a shed I can use for jobs like this. The first thing to do was to move the engine into it, which was an interesting job involving a wheelbarrow ! I put the engine on a table that's in the shed for an initial assessment and clean.

As you can see, the engine is cosmetically poor. It's been standing for a long time (actually, around 15-20 years), and for some of that time it was outdoors under a tarpaulin.

Obvious problems include a lot of rust on exposed steel parts and furry white corrosion on alloy bits. There's also the original reason I removed it from the bike, which is that the thread on the output shaft was badly damaged when the sprocket dropped off while the engine was running. I am hoping it might be possible to re-cut the thread, but it might be a case of splitting the crankcases to change the output shaft completely.

The first job is going to be giving the outside of the engine a good clean. This won't be to restore the original finish, just to clear off the debris of decades so that when I start opening it up I don't end up with dirt getting inside the engine.

The toothbrush you can see in this photo is one of my favourite tools for this - I just use it with clean water to scrub the alloy and it removes most of the surface white furry corrosion.

After doing this for a little while, I realised that the table was maybe not strong enough to hold the engine's weight. Oops ! So I moved it onto the shed floor. As you can see, the table has acquired a few dents !

I'll update this project as it progresses. Don't expect it to be a quick process - it's a winter project, which I'm planning to do at a relaxed pace, and fully accepting that there may be nasty things I find when I open the engine up that stop the whole process dead in it's tracks .

Z650 Engine Rebuild Winter Project - #1: Initial Assessment | Ecency