tapping/knocking engine advice

[unblind]

Quick history- recently picked up a 1990 with 18k miles, been in storage 4 yrs. Got it home, pulled gas tank,drained ,cleaned, pulled carbs and totally cleaned then sync-d. Fresh oil and coolant, bled brakes and clutch fluid and we were going. :eusa_dance: My first Vmax and I am hooked and already looking at upgrades.

All was good for about 350-400 miles. Checked the plugs last night to see how was burning, 3 were great 1 was kinda sooty but not horrible. Reinstall them, and suddenly, get tapping from left front cylinder. Went for quick ride to see if maybe will warm up/quiet down and was running ok aside from new tapping sound. Pull over and sound was getting worse! :bang head: Eased my way back home and really didn't like the clatter coming from engine. No other areas of engine sound like this only the aforementioned left front, coming from under the valve cover area.

Could something tiny have fallen into plug hole and causing such a racket from valve area? Maybe crud still finding its way into carbs/engine from old tank and/or lines? (Still adding Seafoam) Maybe just coincidental timing?
When I do tear into it what should I look for?
Any and all advice is appreciated.

 

[Damon]

When one cylinder is NOT firing it may cause this type of tapping sound. I would replace that sparkplug and/or confirm the slow speed fuel circuit before tear into it!

 

[one2dmax]

Agreed. Though there may have been debris that fell into the cylinder when the plug was removed/replaced and the gaps are very tiny between piston and cylinder head so it doesn't take much to beat stuff up in there.

Sean

 

[MaxMidnight]

Possibly a stupid suggestion but is the spark plug in tight enough to make a seal?

 

[SpecOps13]

My vote's for crap in one carbs idle circuit... Hope I'm right for your sake.

 

[wlodek1980]

possibly a stupid suggestion but is the spark plug in tight enough to make a seal?

+1

 

[Miles Long]

When one cylinder is NOT firing it may cause this type of tapping sound. I would replace that sparkplug and/or confirm the slow speed fuel circuit before tear into it!

Can't a cylinder thats NOT firing be easily detected by measuring the temperature of the exhaust port, with a digital infrared gun? Sean???

 

[one2dmax]

Yes, unless you have the OEM header pipes. The front are double walled and not easy to get a reading on.
Sean

 

[unblind]

Thanks to all who responded.
I'm quite sure plugs were in and seated but gonna replace with new plugs.
Hopefully it's like someone mentioned - an idle jet clog not letting one cylinder fire. It just sounded worse than that to me?
Will install new plugs and clean carbs one more time and hope for the best.

 

[[email protected]]

Is it possible the plug boot wasn't completely seated or the plug wire was pulled out of the plug cap or coil while messing around?

 

[tugla]

when you got the plugs out, if you had a small bore scope to take a peak inside to see if anything looks out of place. not sure if you have anyone close to you that you can borrow it. wish i had one, last employer did and we used it all the time, what a life saver for sure.

 

[naughtyG]

Also possible that the sealing washer on one plug broke/fell off, so that the plug ended up screwing in deeper and electrodes were being hit by the piston.

New plugs would fix that for sure.

 

[Damon]

One simple item we forgot to have you check for is an exhaust leak? An exhaust leak @ the head pipe to a exhaust port can create a sound just like a tapping?