Adjusting 1977 Suzuki GS750 Valves

| 8/9/2016 12:00:00 AM


Suzuki’s 1977-1983 2-valve 4-cylinder GS series engine was one of the best. Whether in 550cc, 650cc, 750cc, 850cc or 1,000cc guise, these air-cooled twin-cam fours were praised when new, and over the years they’ve proven themselves to be remarkably robust, able to withstand gross negligence and abuse. That’s good news, because it means that with proper care, you can expect a GS to run, well, almost forever.

BikeMasterAn often neglected maintenance item on these engines is valve adjustment, although experience shows that gently ridden machines tend to hold to spec for tens of thousands of miles. Our subject 1977 Suzuki GS750 is a perfect example of this. An original condition survivor, it shows a low 12,500 miles on the odometer and looks like a bike that was only ridden when it was nice outside, and put in the garage when it wasn’t. Checking the valves confirmed this: All the valves were within specification and no adjustment was needed.

The valve clearance (or lash) on the 2-valve GS750 is very tight; 0.03mm-0.08mm, or 0.001in-0.003in. Loose is better than tight, and in our case the valves were all on the high end at 0.0025in-0.003in. The valves are shim over bucket, with adjustment shims carried in a recess in the actuating bucket. Removing shims requires the correct valve shim tool, readily available from Motion Pro for $16.50. Shims are available from various sources individually or in kits, with individual shims costing $12-$15 and kits around $75-$100. Local shops typically stock the shims, and once you know what you need you can usually purchase them from the local Suzuki dealer or independent shop.

You’ll need a good set of feeler gauges, making sure the set includes the thin sizes needed for the Suzuki. Besides that, all you’ll need are standard hand tools. The actual checking doesn’t take too long, but be prepared to either let the bike sit as you locate the necessary shims — or do the job twice if shims aren’t available locally and you need to keep your bike on the road while waiting for them. As always, have a good manual at hand to confirm proper specifications.