Make Dre-XT-Stueck great again - engine (part 2)

With all that work in the suspension department, it only seems fitting to up the ante a bit in the engine department as well. For this reason a 55W XT600 Tenere engine has been acquired. I didn't know exactly a lot, except that it looked a bit nicer than I expected and it had been taken out of a running Tenere ten or fifteen years ago.

An inspection with an endoscope revealed that the right inlet valve had lots of oil deposits on it and quite a bit more play than the left one. So I gambled a bit and decided that a fresh set of aftermarket valves, new valve stem seals and a quick hone of the cylinder should do it for now.

The exhaust valve covers were properly stuck.

Hammer, chisel and brute force was called for.

Rockers and cam aren't new, but well within usable spec. Even though I think someone was a bit sloppy with oil-changes or ran the bike a bit low on oil.

My standard trick to get the piston closer to the cylinder head's squish band didn't work in the end as the piston only sits 0.4mm low and with approx. 1mm for both head- and base-gasket combined risking things with only 0.9mm of clearance on a roller bearing engine appears to be a bit daring. Especially as the squish has probably worked quite well judging by how clean those areas on the piston and head were.

With a bit of solvent and a lot of manual labour, the cylinder head cleaned up nicely and in the end I only had to replace one inlet valve and the valve seats actually looked very nice.

The piston had some marks on the skirt and lots of carbon buildup on top and most importantly a stuck oil-scraper ring, which probably together with that one inlet made for a very smoky engine.

From being parked for such a long time, the rings had left quite some marks in the bore and even a light hone job didn't get them out, BUT it should have broken the edges of the marks. (Ultimately this engine will grow some sort of high(er) comp piston and cam anyway...)

When I took off the left foot peg, I had a bit of a shock as water started dripping out. Now this isn't my dad's CX500, which are known to have their frames rust to bits, but still maybe a drain hole would be a reasonable addition.

One thing to note: Contrary to what some XT600 engine swap pages say, the 55W and 43F run the same alternator and ignition. (Thank me later)

Another pro-tip (thanks to my dad for pointing this out to me): Install the carbs, whilst you only have the swingarm/upper rear engine mounting bolt in. The extra space makes installing the carbs an absolute breeze.

Bit of dielectric grease on the connectors won't do harm either. I hadn't encountered any issues (yet), but they did look a bit crusty to start with.

Pre-lubricating a dry-sump engine prior to the first start is always a bit nerve-wrecking. This time we filled about 0.5L of oil into the engine via the breather to give the oilpump some fresh oil to pick up.

And also filled the oil-filter housing with a syringe and the rest into the oil-tank as you usually would. 

Couple of kicks...

... and it's job's done. Now the 600 has definitely got a lot more torque, it was a bit too cold for a decent test ride and also during disassembly one of the inlet rubbers fractured and was only hastily glued together with some engine silicone.