Topic: Engine Noise - the sequel

[Canuck Cafe]

Hi Guys,

Thanks for your suggestions in my old post....most of the noise was the cam chain tensioner.  It was adjusted properly last night using TDC on #1.  Timing was strobed and spot on, valves were adjusted and all were too tight.  The sputtering in the motor was due to old gas, and with some fresh 93 octane in the tank, it's responding quite well.
 
As the engine was turned over for valve adjustment using an wrench, the valves seemed quite noisy and were not smooth in their travel up and down.  They seemed to stick a little and then slide quickly, then stick again and all of this caused a fairly loud clicking noise.  This even happened when the motor was turned smoothly with the wrench. 
 
What would the cause of this be?  I'm figuring it could be the valve springs.  Should I be concerned about this?

[Tim.]

I'd say you should be concerned.  If a valve doesn't spring back up into it's position when the cam rotates, there is a possibility the piston will come a callin' and smash right into the valve.

Your valve springs serve to keep the valves closed and to get them closed as quickly as the cam lobe allows.  There's nothing about the spring that I can think of that would result in this, except if there's some interference between the inner and outer springs somehow.

I'd think more along the lines of your valve guides and/or seals.  I wouldn't run the bike if you can actually see your valves moving inconsistently.  Your piston might even be pushing it closed, and if that's the case, when running, you're going to be chewing up metal.

[HondaMan]

If the bike has been sitting a long time, the valve stems can get quite sticky and cause a similar symptom to what you're describing. Particularly when the valve adjustments are too tight: this causes carbon to burn onto the (overheating) valve stems at the point where the stem is supposed to enter the guide, but now it has trouble doing so because the carbon has reshaped the valve stem at that spot. The single-cylinder Hondas were famous for this.

While it's possible to get them moving again without disassembling the engine (if this is the situation), it's a pain. It goes like this: get some BG44K and mix about 20% of the can in a full tank of gas. Run the engine at low speeds (under 3000 RPM) until the gas is gone, and repeat until the BG44K is used up. It will eventually clean those valve stems, but you'll likely go through several sets of spark plugs in the process. And, it will take a while.

Disassembling the head and manually cleaning off the valve stems on a wire wheel is the fast way.