The 01-03 rocker arms were pressure fed.
In 03 the rocker rollers were updated with 7.8mm pins as Taffy has described.
It was a common upgrade to use the 03 rocker assemblies in 01 and 02 models to increase longevity of the bearing. A probably larger contributing factor to premature roller rocker failure was the aggressive profile of the camshaft. In 2004 the cam was mellowed out and didn’t beat the rollers to an early death. The 2004 Cam, Cam Sprocket and
Autodecompression Device would be a nice upgrade for your 01 (with or without the 03 rockers). This may allow you to remove the kickstart activated Decomperssion parts as the 04-08 ADC system works very well.
It appears that one of your rollers was replaced. The peening done, to fasten it to the arm, should have been done in the center of the pin and not on the arm itself I believe.
Before you sink a ton of money into a 01 it would behoove you to read every post ever written regarding a 01 and also the Wiki.
On the bright side, yours is a FC and you will not have to contend with trying to get it (a 01) to e-start. That in itself SIGNIFICANTLY reduces the number of issues you will be presented with and may make for a worthy endeavor (fixing the old girl up).
Eric
In order of your reference:
Pressure fed rockers: I might be in trouble now (jumping the gun on preventative failure); having seen Taff's video on drilling top side of rocker arm with funnel type catch cavity to increase oiling (did I sabotage oil pressuring ability w/ 1mm final drip hole)?
Rocker Bearing: Now knowing one was replaced (peened in error) shouldn't the issue w/ remainder be simply the outside diameter of the new replacement bearing (presuming updated needed size within same)?
Rockers: Depending if I ruined current w/ drilling hole or not, prefer to keep rockers, avoiding 03, replace remaining bearing.
2001 investment and overall scheme: Received bike via defaulted loan, repo if you will. Non running, failed stator. New stator, got it running w/ rough timing, kid tried to start, kicked back which broke both ankle bones. Bad start, sat for a while, all in now. Removed kickstart decomp system, fixed starting prob. Bike runs good missing power only prob. Plan was to update known issues, sell it. Now might keep it if reliability and failure avoidance can be managed. Low hours, AAA condition.
Research sourced intended fixes: Either change cam and updated rockers (and bearings therein) or dual valve springs. Go to steel cam gear, new chain, updated tensioner, replace remaining rocker bearing, new cam bearings. 01 parts failure risks identified XXX fingers I have an exception or keep use to minimal (have kx500 and wr450 also, only 1 rider to use all), Photos next