GS673 Conversion — Cleaning The Crankcases and Painting Engine.

The 673 kit.

The next step for the GS550 is to relieve the crankcases slightly so that the bigger diameter liners will fit inside. I'd just ordered a new Dremel as my old Draper version was getting a bit tired. That thing has been amazing and I've had it almost twenty years — it's done lots of porting and polishing. Anyway, i was in the process of grinding out some of the casing when the Draper tool finally gave up and spat chunks of plastic out the side. The Dremel came just in time!

If you're wondering about the quality of the deburring tools, sandpaper barrels etc., the Dremel ones are superb! I've always bought the cheaper versions and they wear out in seconds, The Dremel ones are worth the extra cost. 

But on with the job. 

I found it easier to slip the cylinders over the studs, turn the case upside down and mark where the liners were touching. Then remove the cylinders and start grinding. Bit by bit, they went lower and lower.

Suzuki GS550E 673 — Stripping the Engine, Decking the Barrels.

And skim the head!

The next thing on the list was the broken fin on the barrels. I cut out a similar shape from some old aluminium that was lying around, then filed it somewhere near. I wanted the barrels to be hot before welding to avoid cracks etc., so a trip to the oven was in order. Half an hour at 150 Celsius was perfect and the liners slid straight out. This was even better because No.4 sat slightly proud before I started.

Roughly shaped, let's take a look.

Suzuki GS550E — 673 Conversion.

Slight Misfire Halts Play!

It finally happened, I knew the engine was on borrowed time, but it's been happily running me around for the past couple of years, relatively drama free. Now, still running reasonably well considering, it's misfiring on one cylinder and after a quick compression test, no.4 was found to be sadly lacking. You could also hear the familiar chuff-chuff out of the righthand pipe from a burnt exhaust valve.

The reason, you may well ask, why this engine was on borrowed time was because there is wear in the camshaft journals, so not ideal to do a top-end rebuild with the original head. And finding another head for one of these seems to be impossible in Australia. Plenty in the UK and America, but postage wouldn't be worthwhile.