XT600 engine rebuild - cleanup of the new cases (Part 1)

So I am helping out with rebuilding an XT600 engine after the slightly dramatic self-destruction you saw recently. As a matter of fact, as I inherited the Dre-XT-Stück myself a bit of re-familiarization with the XT600 engine won't exactly do me harm, mainly because I want the Dre-XT-Stück to ultimately grow into a 600.

If there's one golden rule to adhere, when someone gives you an engine in parts. Never believe anything until you've proven it yourself. In this particular case it meant cleaning everything even down to the oilpump strainer mesh and I found: Not much. Bit of dust from this engine sitting in a shop for at least a year or two. 

Guess what? Some people have all the look and find an XT600 gearbox with no discernible wear on it for 100 Euros. 

As the engine came with a load of seals and o-rings in original Yamaha bags AND there was a lot of oil around the gearbox selector seal, this one was quickly swapped.

Cases testfitted with the gearbox in. All seems to be there AND working. Unfortunately I couldn't permanently button it up as the gasket between the oilpump strainer and the engine case was missing and I didn't want to use RTV there.

So once the missing gasket has arrived the cases will be RTV'ed and bolted together and then it's really just a matter of throwing some more parts on it and see what sticks and what doesn't.

Project SR500 "intermission"

There is a Greek proverb: "If you want to make the gods smile, make an ambitious plan." Well, this little project was meant to go along the same lines. Just quickly throw together the left-over SR500 bits into a bike and then get rid of it. (As nobody was interested in buying the individual parts!)

So here goes, German 2J4 with from 1980 (so pre-AU), with my spare-parts donor engine re-assembled into an actual engine again.

I started off with a frame I was given ages ago, when I picked up my SR500 sidecar.

Nice surprise, there's even usable air-filter inside the airbox.

One of the missing bits were the forks. My original spare SR500 forks went into the XS400 ratracer two or three years ago. So new bearings and a copious amount of grease...

 ... et voilá: frontend!

Not sure why there was no swingarm in the frame, but same story as with the headstock: Lots of fresh grease and a bit of work later and it's actually done.

I think these are the original XS750 shocks, I wonder how well they will perform. 

Rear-wheel fitted, all looking very good so far.

One of the bigger question marks was the engine. I was pretty sure I had everything except the ignition, but the only way to find out was to go through a lot of boxes and find out the hard way.

First cleaned the original cylinder head of my SR500 hack, which I knew had a good cam, rockers and valves in it.

Then gave the cylinder a quick hone, just to give those rings something to "bite" into.

Unfortunately, I was in fact missing a base gasket, but I did have two head gaskets, go figure... So it was time to make my own. An annoyingly time consuming task to be honest.

Yes it's a used piston, but the clearance is still pretty alright and the rings had nice tension.

All timed up.

Bit of moly grease to protect the cam and rockers during initial startup.

It's bizarre, even though it's not a huge step forward in the grand scheme of things, once I have put the engine in a bike, it feels a lot more done than it actually is. 

So, yes this SR500 is for sale. Is it complete? No. But I am convinced you will hardly ever get a better insight on what you're actually buying. It would make a perfect base for something a bit more individual, not so much as a restauration piece. Personally, I think I'd love to turn this into a vicious little minimalistic bar hopper. I also have some sporty bits, like a flatslide carb, hot-cam, big-bore cylinder, that I could throw in as part of the deal... just in case you're interested.

XT600 carnage

Carnage that's quite a word isn't it. Even more so, if the term is applied to an XT600 engine. This engine belongs to a friend and we basically dissected it to hopefully salvage the gearbox.

[Spoiler alert: that didn't work.]

The engine on its own didn't look too bad and even the starter was still spinning, when you pressed the button...

 Uh oh... that's the woodruff key cleanly sheared off.

Head did have some oil in it. Camshaft bearing surfaces are definitely shot.

But on the contrary those rockers are well usable again.

Now we're getting close. Rings stuck, piston skirt massively scratched. (No picture, but the cylinder is definitely salvageable with an overbore.)

Now we're definitely getting closer: Look at the lock-washer on the crank gear, that's bent over.

And this must be the infamous Yamaha Crankcase Ventilation System (YCVS)!

Obviously the counterbalancer and the crank became a bit intimate. No reports whether kissing happened with or without tongue, but definitely without mutual consent.

The bit poking up: That's the cast material around the bearing of the balancer shaft.

So,  is this ... the Summer edition?

All that is left in the end...

... and yes it was meant to look a bit like a splatter movie.

Next update will be on "project intermission" - curious? Nah, me neither. 😜