The Kawasaki engine on my John Deere GX345 needed some work done. It has removable heads which have the Intake & Exhaust valves.
I was in need of something to compress the valve springs to get the "keepers" out and remove the valves to replace the stem seals.
There are commercial valve spring compressors like the Lisle 2330. But, I enjoy a challenge and thought I'd make my own.
Started with a Quick-Grip 6" Mini bar clamp, some tubing and some flat stock.
The Quick-Grip has plenty of force to compress the spring(s), then it's just a matter of not losing the keepers.
A magnet was held nearby to catch the little buggers.
While waiting on parts for assembly, I kept the valve, valve spring, spring cap & keepers together by clamping a binder clip on the valve stem with the other parts in place.
The idea should work for other engine heads that have the valves in them. A regular 6" QG clamp would have more force for bigger springs and more depth to clear the head if they are larger than what I show.