Valves re-shimmed, now exhaust burble- thoughts?

Finally got the kz750's valves re-shimmed (6 out of 8 out of spec) and put back together. Over 5 stinkin' hours scrapping off the gasket, yuch! Bike runs like a champ though so I'm happy I did it. Next time I'll get this stuff done during the winter so I can enjoy the Spring riding weather.

Anyways, one change that I've noticed that once the engine gets warmed up, the exhaust sort of burbles and pops when it's at idle. It idles fine and it's not too bad, just not sure how adjusting the shims would cause this, or if something else I did is doing it. I did have to remove the tank, coils, and pollution control system to get the valve cover off.

Any thoughts?

depends on how long the valves were out of wack somebody might have played with carbs thinking that was the problem previously

I recommend double checking the hoses that lead to the pollution control equipment. Perhaps air is being sucked in through a cracked hose.

And how were the valve clearances before you changed shims? Were they all too tight so that you increased the clearances, or did you adjust any to have less clearance than before?

I have found that if you take several readings for each valve, with the cams at several places through their rotation, that you may get slightly different reasults. I usually use the tightest reading for reference, and then choose a shim thickness so that new clearances will be on the loose side, rather than too tight.

If you made a clearance too tight, it will cause a funny sound because the valve will start to leek when it gets hot. You are better off to be a little on the loose side than on the close side.

Thanks guys, 5 of the valves only had .02-.04 mm clearance, one had no clearance and I had to replace that tappet. Now they're all between .13-.18 mm. Since I had the carbs balanced and fuel/air mixture adjusted last Spring (stupidly before I checked clearances), Plummen could definitely be on to something. I did check the clearance several times, rotating the crank a couple of times between checks, but I always checked at TDC, like the FSM says. If it doesn't clear up, I'll open it back up again.

Thanks for the advice!

I'll check the hoses, I definitely had to muscle them around to get them in