Noisy valves and spark plug length?

[yoda731]

Hey, folks.

I have adjusted my valves several times and am confident that they are at the factory spec. But, I still have some tapping/clatter, especially once the engine is warmed up. In diagnosing further what this could be with my Clymer's manual, I saw a note on spark plug length. The note says to be sure the plugs are the right length. It doesn't say what that is. It states that if the plugs are too long at the bottom (too many threads) they can interfere with the valves and pistons. The have a diagram, but again don't specify any length to get.

When I changed my plugs, the set I put in were about a 1/8in longer than the set I took out. This concerned me, so I double-checked the website for Autolite (the brand of plugs I bought) and verified that I had the size they recommended -- 4164. Having done that, I confidently put in the new longer set and figured the other set was too short (They were a bit fouled, I thought that was related either to length or valves out of adjustment...).

So, am I OK since I have the recommended number, or is possible I have the right number but wrong length of that number? Hope that makes sense.

As a note, I have inspected the plugs a few times since, and they are clean with no fouling to speak of.

Related-- I am confident that I have my valves adjusted correctly to the factory spec. Is it normal to still have some light tapping from the valves, especially when they are warm?

FYI, here is where I double-checked I had the right plug before installing it.

Thanks as always!
JC

[Pongo]

If the plug is too long it will quite likely damage valves or pistons.

This is the plug for your bike.

NGK/DR8ES-L Spark Plug - Honda CX500 CB Custom

[TheImp]

The general thought is that its better to hear them than to not hear them because a the wear and tear with looser valves is usually not as bad as when they're tighter and you cannot hear them.

Funny thing is today I redid my valves again for the second time and it sounds much better than the first time where I had it too loose but I still get clatter. When I use the feeler gauge the first one that is next thicker than the limit for that particular valve, if it slides into the valve stem but I have to pull hard and it scrapes the feeler gauge is what I found is within spec. But I really don't know if my method is right or not either because I do get clatter.

Please, if anyone here can offer more advice than I've gleaned off of books and the internet on how much drag I should be feeling please let me know. I might consider doing the valves for a third time or posting a sound file so folks can hear the engine and let me know what they think.

[jmillheiser]

Hey yoda. Make sure your using the proper unit of measure on your feeler gauge. .10mm on the intake and .12mm on the exhaust are the spec for the CX, this translates to .004in and .005in on an SAE feeler gauge, it is pretty easy to end up using .008in and .010in by accident which will make for loud valves. I suspect the previous owner of my CX500 made this mistake when adjusting the valves, after I got them adjusted to .004in and .005in they got much quieter.

It is normal to hear a little quiet clatter from under the valve covers, but not a loud clatter.

if your valves are way loose it will also reduce your power slightly as your losing cam lift.

[TechTMW]

Please, if anyone here can offer more advice than I've gleaned off of books and the internet on how much drag I should be feeling please let me know.

This is exactly what I was talking about when you were asking about your valve cover.

take a strong magnet (Like a pen-sized pick-up magnet for nuts and bolts) and run the feeler gauge over the magnet. It has a feeling of "Magnetic drag" There is slight friction - you can feel the magnet pulling on the gauge.

Now, when you get the gauge between your valve and cam / shim / rocker, whatever - you need to make sure that the feeler is perpendicular to the valve stem (90* angle) for a proper "feel." When you adjust the valve, you should feel about the same amount ot "Pull" on the gauge as you felt with the magnet. Not too tight, but not loose. You MUST make sure the feeler is at a 90* angle to the valve - if it's off a bit, you won't get the same feeling because the gauge will be pinched.

[yoda731]

Thanks for the feedback. About the spark plugs though-- I am right that a given spark plug (like my Autolite 4164) only comes in one length, right? So having correctly matched that part number, I have the right length?

JC

[yoda731]

Hey yoda. Make sure your using the proper unit of measure on your feeler gauge. .10mm on the intake and .12mm on the exhaust are the spec for the CX, this translates to .004in and .005in on an SAE feeler gauge, it is pretty easy to end up using .008in and .010in by accident which will make for loud valves. I suspect the previous owner of my CX500 made this mistake when adjusting the valves, after I got them adjusted to .004in and .005in they got much quieter.

It is normal to hear a little quiet clatter from under the valve covers, but not a loud clatter.

if your valves are way loose it will also reduce your power slightly as your losing cam lift.

Thanks. As a note, my Clymer's manual has my settings at .004 and .003 for the exhaust and intake respective. In the "1981 and later models" addendum, it lists .005 and .004 as the measurements for some of the 650 and other newer models. Do you know of something that still indicates .005 and .004 for my bike?

JC

[DRam]

Greetings all. I'm new on the board and am enjoying the site. My opinion, for what it's worth, about setting valve clearance is to use the go / nogo system. If your clearance is supposed to be .003, set clearance using the .003 guage. Then try to slide the .004 guage in. If the .003 slides in, but the .004 doesn't (as in you have to force it in), then you have a slightly loose .003 setting. While the truly ana insist on exactly what the spec sheet says, I prefer a slightly loose setting to one that might be tight as too tight can cause burned valves.

Alternatively one could set the .004 guage to a fit that requires a fair amount of force to pull it out, see if the .003 slides in easily, then try to reinsert the .004. If it doesn't go you have clearance between .003 and .00375 or so.

[yoda731]

...FYI, here is where I double-checked I had the right plug before installing it...

Guess I forgot the link:

http://www.autolite.com/pdf/Motorcycles.pdf