So, at the begining of all this, Allen was saying his new (to him) ST1100 had a little... how was he saying it.... like, he felt the engine wasn't running exactly as smootly as it should.
Was it a kind of slight knocking he could felt ? I will have to recheck the first video.
And this is one of the reason he went thru the unbuild, inspection, and rebuild of the engine.
What did he found ? Two things.
1- That oil pump rubber bushing that was squeezed, smashed in place, and a bit deformed, from the factory.
2- A bearing connecting rod ( # 8 ) that was rubing a bit inside of the piston rod assembly ( # 4 ). Or was it rubbed from the inside by the crankshaft ? Anyway...
That part is called a bearing, but it is a different kind of bearing. Not a ball bearing like we are used to see. It is just a curved flat piece of ... aluminium, or some kind of alloy.
We could see a little spot inside the part, where it was very slightly worned out. So the two parts where just slightly rubbing each other at a very little spot.
And that is only on one of the four piston connecting rod / bearing ; the connection point between the piston rod and the crankshaft.
By checking the thickness and the loose space with the tolerances given in the service manual, he saw that this one bearing was not exactly of the correct thickness.
Those bearing comes in different thickness, with different color codes.
And he was saying that one in particular, who was green (like all the others) should had been brown. And he replaced it with a brown one.
And remember this engine is still almost new : only 17 000 miles.
After the rebuild, his engine now runs like a charm.
So, surprisingly ( for a Honda ) it look like it was an incorrect assembly, a mounting error, from the factory. And one not easy to detect.
If I remember correctly, he said that particular rod bearing was a bit of a tight fit for the green color. It was a bit marginal. The brown one was more in the specs, for that particular piston rod.
I'm still amazed by how he was able to detect and feel that a little something wasn't exactly right.
It must had been very subtle. Maybe just in the sound the engine was making. Specialy when you think that the point of friction had worned out.
I guess when you are designing and building engines, like he always did, you're getting a sixth sense for that.