Engine "Clicking" and Spark Plug Gap Relation

Kioshk

Kioshk

Active Member
Hey all,

I've been running an X80 recently, and have about 1000 uneventful miles on it (about 40 miles a day now). The engine's been running great, although under load after it's heated up, it would click rather sharply much like it would with something being rattled around in the combustion-chamber. Having already dealt with destroyed cylinders/rings/pistons, I was alarmed and immediately tore the engine down. I found that everything was just fine; in fact, the lower needle-bearing had almost no play. The case was clean, and piston/cylinder/rings were unsullied mirrors. I had an enclosed HK1015 needle-bearing on hand that I was anxious to try out as a replacement for stock, and figured it may stop the "rapping". It didn't, although the engine runs smoother and with less vibration now...especially at higher RPMs. Anyway, I was still baffled by this rather loud mechanical clicking that wasn't physically affecting the engine, and imagined it MIGHT be detonation, but this is my third engine, and I am pretty darned sure that the compression in this one is too low for that to be happening (the head-gasket that came on this one was THICK...almost 2.5X), the head is tightened down adequately. Also, the plug is well clear of the piston, and it's a lovely cocoa-brown. Tonight I decided to try a gap-change. I've been running at 0.27 since I got this engine, so I bumped it up to 0.32 to see what would happen. Well, I was disappointed at first, since it took longer than normal to get the engine revving, but after a short distance, it began to respond really well. Also, the clicking was nearly imperceptible. To my delight, once the engine was up to operating temperature it was actually PULLING with acceleration in the upper ranges. Did I miss something? I'm mostly curious as to what that damned clicking was. I'd convinced myself it wasn't harmful to the engine, but it was damned annoying, and had the risk of masking important "diagnostic noises" so I was ever alert which detracted from the pleasure of riding. Any clues?
 
Cooler weather out side lately as of your latest test ride? Do you have a higher compression head on the engine? The clicking sound can be detonation on hotter days.
 
I've noticed something like that at WOT lately, like extra snapping sounds, gives my ears concern.
One of my thoughts are arcing from the crappy spark plug wire, I already checked the head and spark plug tightness, another theory is my CDI may be going bad?

Detonation?
Need to tighten my chain (chain slap)?

Maybe I could do what you did, now if I could find my gapper.
 
when that happened on mine I had to trim the gasket back since the piston edge was contacting it. you can tell where it hits because it leaves it shiney.
possibly your rings are semi-snagging on the exhaust or transfer ports. Some cylinders have sharp edges at the top of the ports. bevel them with a fine roundish file.
 
A wider plug gap retards the ignition. Not by much, but maybe what you were hearing was slight pre-ignition because the plug was firing a little ahead of time. By increasing the gap it takes a mili-second longer for the CDI to provide enough current to jump the gap. Just a theory, but based on fact.

Tom
 
Thanks for all the advice, fellows. I think Tom may have hit it on the head. Everything else in the chambers was fine...no interferences at all, and as a precaution, I re-ported the exhaust/intake to assure no ring hangup...wasn't the issue apparently. I should note that I'd also just replaced the CDI due to another issue (the previous one died), clicking continued after replacement.

Well, this is my third engine; you never stop learning. Gotta say, it's running great now. Clicking's gone, and it's powering up hills well.
 
crassius said:
always wondered if changing CDI would change timing by a degree or two
Click to expand...
If you mean in degrees of crankshaft rotation, no. There can be manufacturing inconsistancies in the CDI but I doubt that they would be enough to notice. A few ohms difference in resistance through a circuit isn't enough to make any difference.

The only thing that will change timing to any significance would be to reposition the magneto rotor (magnet) on the crank. The jury is still out on those over priced CDIs that 'claim' to have an adjustable performance curve.

Tom
 
I have had my 48cc clicking like that for over year now and every thing in the engine look good.I went out to the garage and gap it at 32 after reading your post Tom and clicking is gone now.All I can say is wow.1 yr with it like that.
 
My Pig has been doing this lately as well, I'll try gapping the plug and see if it stops.
 
not really resistance alone, but if there is a 10% tolerance on the parts in the firing circuit, it could make a diff - not that I'd impune chinese quality
 
Well what mine was doing it was only clicking at low rpm like the idle it was bad enough to kill the engine but if I raised idle a little it would go away. So I always had a higher idle then wanted. Now it gone thanks to the people on here. I've been on here a little while and still learn stuff.
 
Opening the spark plug gap did not change the noise on my Pig, so I pulled the head and found the head gasket shiny as described above. I removed a tiny bit of the edge and no more noise!
I cannot imagine why this would start AFTER the engine was running and well broken-in, but I've learned the ht's are...shall we say...a little bit "unusual".
 
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