Motorcycle Repair: Sportster (91) Bottom end, valve stem oil seals, adjustable pushrods

Question
QUESTION: Hi,
I have a '91 XL883(1200 Conversion,Crane "Street" cams, Manley valves, Screamin Eagle Ignition module, H-D performance pipes).
It was smoking quite a bit, but only at idle so I stripped the top end and found the exhaust valve stem oil seals had gone. The heads were sent away to get the valves fitted as whoever did the conversion made a right mess of the heads. The guy doing the job was amazed it ran at all, let alone pull as well as it did. That's all sorted and the top end was rebuilt with Genuine H-D rings & gaskets with S&S head gaskets. Fired it up and it ran just fine. I had a TOP END TAPPING sound appear about 200 miles BEFORE the top end re-build and that was still there, so I planned to fit adjustable pushrods when I re-torque the heads after a few hundred miles. I had an oil weep from the rocker cover bolts(copper and fibre washers), so I added a small o-ring. I took the bike out to check this had worked and gave it a fair blast. Got back and checked for any oil weep..none, so that was sorted. Put the bike away.
Next time I start it up there is a knocking sound that appears to be coming from REAR of the BOTTOM END (behind the front belt pulley cover. If I listen at the OUTLET of the FRONT PIPE I can hear what sounds like someone hitting the end of a metal rain water drain pipe. This sound is NOT AUDIBLE at the outlet of the REAR PIPE.
The original tapping sound only appeared when the engine had warmed up. It got louder when accelerating and seemed to lessen significantly when coasting along or decelerating.
I have a feeling the main bearings have now gone. I hope I'm wrong but I can't imagine a top end issue giving these symptoms. Anything else that would give this sound ?  Thanks for taking the time to read this. Regards, Gareth

ANSWER: I would pull the top end and check the rods. Sounds like you have a rod bearing going out.
A piece of advice, once you torque the heads do not retorque. Good way to blow a head gasket or stretch a head bolt.
Good luck and happy riding
Mike

---------- FOLLOW-UP ----------

QUESTION: Thanks Mike, Just to clarify..are you refering to what I would call the con rod bearings (ie. small and big end)?

If this turns out to be the cause of the knocking sound(approx. half engine speed), do you think the original "tapping" sound was the early stages of bearing failure.
Due to the failed valve stem seal and the increased oil consumption, I used a cheaper 20w50 oil for a month or so prior to the "ticking" sound appearing. False economy, eh ? I've been in contact with other Sportster owners that have the same front top end "ticking" sound that appears when the engine warms up. Most of them had the noise appear after straight forward work like replacing rocker box gaskets. Most of them at their local Main Stealer.
Thanks for the "Do not re-torque" advice.

Answer
What you described was two different sounds. You said a knocking sound and a tapping sound. A knocking sound would probably be a rod bearing.(the connecting rod) If you have a tapping sound it could be just a lifter that is tapping. If its a lifter it will not hurt anything, just annoying
Good luck and happy riding
Mike