Is the shim exchange dead?

[Grimly]

When I had my '79 850G back in the 1980s, I religiously checked the valve clearances and over of the first 50K km (I am Canadian) all of the shims were changed.

After that, the dealer told me that the clearances were unlikely to change and so I could safely just forget about it unless the bike started running poorly in which case, bring it back. I eventually sold the bike with more than 100K km (about 63,000 miles) on it - and the last check I did showed no change in clearances since the 50K km check.

Has that been anyone else's experience or do the clearances continue to open or close-up over time?

I found the same, over long distances of mostly stable revs the clearances hardly altered. It got to the point where a check every 20K was really just an advisory.
However, when I stopped doing that and started using the bikes in what might be called normal use, the checking interval reared its head in a bad way, with a reminder that things had changed. I now check them every 6K or so, sometimes shorter or longer depending on useage.

[Nessism]

Typically, the clearances close up with mileage. And when all the clearance is gone, the valves hang open which can lead to damage.

One of the first signs of valves starting to hang open is hard starting when hot. Keep riding, and the valve will burn and likely crack. Not good.

I don't think Suzuki did anyone a favor by specifying such a tight valve clearance range - .03-.08mm. KZ bikes, with virtually the same valve train design as the GS bikes, use more than double that much clearance.

[MaxPete]

Typically, the clearances close up with mileage. And when all the clearance is gone, the valves hang open which can lead to damage.

One of the first signs of valves starting to hang open is hard starting when hot. Keep riding, and the valve will burn and likely crack. Not good.

I don't think Suzuki did anyone a favor by specifying such a tight valve clearance range - .03-.08mm. KZ bikes, with virtually the same valve train design as the GS bikes, use more than double that much clearance.

Thanks folks - some great advice here.

As for the tight valve clearances, my guess is that Suzuki was trying to keep the engines quiet and also, these late 70's GS bikes were really their first four-strokes so they were gaining experience after being a 2-stroke engine builder. I think they were also spooked after the RE5 debacle which nearly killed the company and were trying to be as conservative as possible on issues like noise and durability.

[rphillips]

I took your stupid dealers advice, "Forget about it unless the bike starts running poorly". That's exactly what I did. Bike started running poorly, I took the top end apart and did a valve job, and all was good again. Decided a valve check would have been waaaaay cheaper and easier... Maybe Suzuki was trying to keep you from going through this, and keep the ticking down..