Picked up a "knock"?

[grayghost]

started my 97' 500e on saturday, started fine (checked oil level after running approx 5min-then let it sit 2-3min and checked-was right on the mark). after letting her warm up, took her out for about a 5mile run (no hard accel/ top  speed probably 60-65mph). no problems, but when i got back to the house i noticed a "knock" or "tapping" in and around idle RPM's- it disappears when you throttle up (i didn't rev up past 3000rpm or so), but when you drop back down to idle, there it is. i 'm  using royal purple 10w-40w (motorcycle specific) the viscosity range is due to being in east texas (we had temps in the upper 70's this last week). the bike has 12,000miles and previous owner maintained the bike well ( i inherited his shop manual, and he logged in every oil/filter change, etc.)
anybody got an idea of where tp start looking to clear this up.
thanks

[gsJack]

That's very common on many GS500s and harmless if it's the infamous cam shaft sideplay knock.  Knocks only when hot and only at idle and goes away as soon as engine speed is picked up to a fast idle or faster.

My 97 had the knock occasionally and I just ignored it for the 80k miles I put on that engine once I figured out what it was.  Quit knocking after I went to the 15W-40 heavy duty truck oils as I recall.

My 02 GS knocked a few times when I first got it but I haven't noticed it since my first oil change to same oils and have over 66k miles on it now.  Not saying a different oil will fix it but it's harmless if it doesn't.

My GSs ran/run cooler on the 15W-40 oils than the 97 did on 15W-50 synthetic I used in it for first 50k miles.  I wouldn't use an oil that ranged over 40 wt in a Gs unless there's a very serious oil consumption problem.

Suzuki has fixed the problem in recent years and there are shims available to reduce camshaft sideplay to eliminate the knock if it really bothers you. 

[grayghost]

thanks jack, that just about describes this to a "t". i'll monitor the situation and see what happens. i appreciate your reply.

[The Buddha]

My 89 started tapping due to cam shaft drift ~35K miles. I measued it to be ~1/4 mm. The thinnest shim available is 1mm. I ran the bike with that noise annoying me till 45K where it had worn to .3mm yea .25mm to .3mm in 10K. At 45K I yanked them, put aluminum on the side of my can towers and ground it down and reinstalled it. Whisper quiet.
Valves that are high on clearance can also make that tapping noise. That have to be set right, cant run it.
Cool.
Buddha.

[Mdow]

ya i think mine does that too im glad i was starting to think i was losing a rod bearing

[The Buddha]

Between starting to think you're losing a rod bearing, and knowing you have a dead motor, its ~2-3 miles. That's a very good self dis-proving hypothesis.
Cool.
Buddha.