Adjusted valve shims - now some weird symptoms

I tried searching around for answers but didn't turn anything up. Recently I adjusted my valves to get them in spec. 4 of them were too tight by one size. I also adjusted the cam chain tension according to the procedure in the Haynes manual but I didn't feel like anything happened when I loosened the bolt.

Up until this point the bike has been running really well the whole summer. So I ride into work the next day and notice some top end "buzziness" that I don't think I've ever heard before. It happens when the engine gets up to a certain speed, not at idle.

Later that day I parked at a store and when I went to leave the bike wouldn't start unless I gave it a bunch of gas and then the idle was unsteady. Stalled a few times trying to start from a stop and the bike was running poorly. Plug #2 showed up darker than the others - not bad, but they were all exactly the same the last time I'd looked. So last night I checked that the enrichment plunger was going all the way back down for that carb (it was) and inspected the piston diaphragm which looked great. After doing that I did about 40 minutes of riding during which the bike ran flawlessly 95% of the time but had a rough patch somewhere in the middle of riding where it felt bogged down and prone to stalling.

My questions are:
1) Does the cam chain being loose ever sound like a buzzing noise?
2)Any ways to verify that the chain is properly tightened on my bike?
3) Could a valve adjustment throw my mixture off on one cylinder?
4) What would explain the seemingly random occurrence of the bike running rough?

The bike has always been fully warmed up when this happened. I haven't had a look at the inside of the carbs yet, but I want to rule out other things unless my symptoms clearly indicate that's needed.

 

Did you re-sync the carbs and adjust the idle mixture screws yet? Those things need to be done after a valve adjustment, as valve clearance affects the vacuum signal to the carbs.

 

I will perform a carb sync and see how that affects things.

 

Just coming back to this idea, does that mean that any bike with carbs that still have the idle mixture anti-tamper caps on has never had a proper valve adjustment since leaving the factory?

 

No, but to get the bike really dialed in, is it highly recommended that you adjust the mixture screws as well.

If the tamper plugs are still in (given the age of these bikes), it may indicate that the carbs have never had a proper cleaning. If the plugs are still there they need to be removed.

 

Technically, YES it does. Re-synchronizing the carbs is part of the same service regimen that includes valve clearances.

HOWEVER: The factory didn't want the dealers fiddling with the mixtures either; so the "official" service procedure only involved valve clearances and vacuum sync; NOT "mixture fiddling."

So it is possible for a "serviced to spec" bike to still have its mixture screw caps in place, yes. Not very likely, but possible.

 

Thank you for the clarification.

Can anyone answer my questions about the cam chain?

 

Certainly.

First off, what procedure exactly did you use to adjust the cam chain?

 

Just something to think about...

I know we don't have the same bike and I'm not very familiar with the Seca but I had a "buzz" happen to me at about 6000 rpm. After weeks of worrying it turns out it was the plastic radiator cover - I must have gotten a rock or something because a couple of fins cracked and it made a VERY noticeable buzzing noise.

Again, just some food for thought. It could be something vibrating somewhere on the bike.

 

Fitz, the procedure I used is as follows:

Having just adjusted the valves I then...
Turned the ignition rotor CCW to align with the "C" with the indicator
Loosened the 12mm cam chain tensioner lock nut
Loosened the 10mm cam chain tensioner bolt
Didn't notice any noise or anything so rapped on the tensioner assembly a bit Still no indication that anything had happened
Tightened down the cam chain tensioner bolt
Tightened down the cam chain tensioner lock nut

After taking the bike out it seemed noisier with that buzzing happening so I did the whole procedure again just to be sure with no difference.