R90s rapping sound

[Rebel]

How about your brake calipers hanging up?

[Major Softie]

My bad, I forgot about those having the DelOrto's on them. I'll try to think of a more "Italian" explanation.

How about your brake calipers hanging up?

Nope, doesn't have Brembo Brakes either.

[KNS]

Hi All

Sorry I have been under the strap with work these last few days.
As to answer the great questions:
There is no ping especially because the motor was apart a few years ago, at that time we check for any movement in the bottom end bearings all be it in a wiggle test.
I changed the oil this evening and there is no metal fragments in the oil.
The timing has been set statically and the valves are set and rechecked.

I am going to ride it this weekend gently to see what happens and change the oil again on Sunday...
Ken

[KNS]

I forgot to mention where the sound is coming from.
The sound is coming from the left side when the RPM's are around 2500.
The main problem is that the rapping is not consistent unless under acceleration....
Ken

[SteveD]

Noises can come from a variety of sources. Sometimes they relate to vibration bands.

The ones that have caught me out in the past include an inadequately screwed in fuel cap rattling. Won't be your issue.
A loose fairing part once and the alternator cover loose can do it too.

Fwiw, pinging would've been my first thought from the description...crook gas, carbon build up, timing nqr.

[Major Softie]

There is no ping especially because the motor was apart a few years ago, at that time we check for any movement in the bottom end bearings all be it in a wiggle test.

It would appear that your definition of pinging is not our definition of pinging. This can often happen with people from different countries all with their own version of English.

When we say "pinging," we are talking about detonation/pinging/pinking/knock. Your comment about the bearings makes it appear that you thought we were talking about something else.

[Bamboo812]

I'd try retarding the timing a bit and see if that helps. If it does, then the problem was most likely "pinging" or pre-ignition.

[barryh]

The most important thing about pinging is not what we call it but when it happens. Pinging (more properly called detonation) is abnormal combustion that occurs after combustion has already been initiated by the spark. As the combustion pressure rises spontaneous combustion occurs in some parts of the chamber before the normal flame front has managed to get there. On an airhead pinging doesn’t sound anything like a bearing knock. The noise you hear is a pinging metallic resonance of the cylinder affected and it is characteristic of the noise that unlike a bearing knock it sounds to be at a faster frequency than the cylinder firing frequency. The reason for this is there is usually more than once instance of detonation occurring in different parts of the combustion chamber on each cycle. At a given threshold of engine load It's unlikely that pinging would begin to occur simultaneously on both cylinders so if it was a single sound per combustion cycle of one cylinder it would sound relatively slow and a mechanically caused noise on one cylinder would also sound slow. The fact that pinging doesn't sound slow makes it easy to differentiate it from noises with a mechanical cause. Once pinging has been heard it becomes unmistakable. I can initiate mild pinging at will by lugging uphill two up. It depends on the octane being used but an argument could be made that if you can't initiate pinging under those outrageous conditions then the ignition may be too retarded or the fuel unnecessarily too high octane.
Does that definition of pinging help to identify if that's what's happening here ?

Pre-Ignition is something quite different. It is abnormal combustion that occurs before the normal ignition spark. Pre-ignition is initiated by glowing carbon or a spark plug that is too hot. Because the mixture is ignited far too early it builds pressure for most of the compression stroke and so can be very destructive melting plugs and holing pistons quickly if not instantly. I don’t personally know or ever want to know what pre-ignition sounds like as I believe if you can hear it then it may be too late. At a guess I would say it might sound like a mechanical engine knock because of the very high loads being imposed on the bearings.

[duantro]

If you have roller bearing rocker arms, make sure your oil hole is installed in the right position on the shaft. I had installed one upside down, and had this exact pinging sound under load. Pull valve covers and check for oil distribution when running.

[KNS]

Thank you all once again.
I have taken the rocker arms off today and think that maybe the roller bearings are at least part of the problem, the second think I have noticed is that the push rods are scored fairly heavily around the push rods which indicates to me that they are rotating in the tubes and not aligned in the center of the cam follower. Could that be my noise?
Tomorrow is the local Superbike race so I will be going for the fun.
Cheers
Ken