valves (I think) tap when warm By hooknose (Read 959 times)

[hooknose]

So, after a little over 1400 I adjusted the valves on my Roketa mc-13-150 because it was starting hard cold and dying at stop signs before completely warm. I set both at .004” and this solved the cold starting issue as well as the dying issue. I have since put a little over 160 miles on it. All was good until my last 10 mile trip into town when I started to notice the taping sound that began after it got warm. I drove home and put it down for the night. Next morning I started it up and there was no tapping so I took another ride. As it warmed up the tapping became audible and increased in volume as full warm-up was attained. I can’t dig into it until after graduation from nursing school in two months but I would like some opinions on the most likely etiology.

hooknose

[Alleyoop]

Are you sure it is tapping noise If it were the valves that were loose you would hear them more when COLD not hot after they expanded.

Are you sure maybe not pinging bad gas and or rollers rattling they do make a metallic sound.
Alleyoop

[Bashan]

Make sure your sparkplug is tight. They can make a ticking noise as compression gases escape.

[Moat]

Apr 19, 2013 22:12:31 GMT -6 Alleyoop said:

Are you sure it is tapping noise If it were the valves that were loose you would hear them more when COLD not hot after they expanded.

That's simply not true.

Although exhaust valves increase in length some when hot, the expansion of other engine parts (like the aluminum of the cylinder head, for example) in combination with the thinner, hot oil virtually always make tappet noise more apparent when an engine is hot - not cold. And don't overlook that the exhaust valve's head will also expand, radially - forcing the valve slightly towards the combustion chamber as it rides up the tapered valve seat, and increasing valve clearance at the rocker tip a corresponding amount.

Not to mention that the intake valve stem is under constant cooling by the passing fuel/air charge.

Exhaust leaks can sound an awful lot like a loose, ticking tappet as well - but I'd guess the noise has a high probability of either being normal (if not too loud?) or caused by something you did/did not do during the recent valve adjustment (like maybe not tighten the adjuster's nut enough, or just setting lash a bit too loose?).

My $.02

[hooknose]

My theory was not tightening the adjuster nut enough, but because it was quiet when cold (which is when I thought it should be the noisiest) I wanted some more opinions. The sound is most definitely not the “normal” noise the engine had made for the previous 1400 miles. The plug and exhaust are tight. When I tightened the adjuster nuts I was wondering if they were tight enough since I was not using a torque wrench.

Thanks for the input, hooknose

[Alleyoop]

Well that surely can happen the nuts came loose BUT now you should hear clattering even at IDLE DO YOU? If the nut or nuts came loose they will make a CLATTER CLATTER CLATTER. But to tighten them you just tighten them nice and SNUGE DO NOT CRANK on them otherwise they will strip Just tight period.

So if it CLATTERS at IDLE the valves are TO LOOSE, you want to hear a nice TICKY TICKY TICKY. We hot rodders have a saying A LITTLE LOOSE VALVE IS A HAPPY VALVE.
Alleyoop

[Moat]

Apr 21, 2013 23:09:47 GMT -6 Alleyoop said:

We hot rodders have a saying A LITTLE LOOSE VALVE IS A HAPPY VALVE.

Correction - "A tappy valve is a happy valve"