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[Steve T]

555
if I were you I would have the pumps to pieces to see if you can find what is the stiff point, have they been lapped properly? As Pete said can you turn them nicely by hand.

[PeteF]

Understood Steve but what's wrong with too much oil to the rockers and head. My understanding is that it will help to cool the head, the hottest bit. I'm not arguing, just putting another point of view.
Excellent job with the filter. Did you leave the original in? I would think it's redundant now.

[Steve T]

Thanks for your views Pete, the original filter is still in place and is the first line of defence in the war of keeping the oil clean as its in the feed, the external filter also acts as an oil cooler being in the breeze, also it adds about 300mls to the total capacity

[555]

Hi. The spindle turn with a fair amount of pressure from my thumb, then at a point real force is needed to turn it. with the pumps removed it spins freely. The pistons move nicely, it could be lapping in or a slightly wonkey spindle

[ric]

Perhaps the larger diameter of the scavenge piston shaft is fouling the pump cavity.

Removal of the disc and plunger should reveal exactly where contact has been made and where the alloy needs to be removed to permit interference free rotation of the disc and pump shaft.

[Tim NZ]

When a piston seizes, partially or to lock-up point, the piston will have not only had it heat-treatment temper negated, but if will also have changed in dimensions with regards to Taper and clearance (looser). It will NEVER be the same.


Simple re-ringing and honing to clean up the scratches/scores will only ever be a stop gap measure, as both ring and piston life will be greatly reduced. Ultimately a new piston will be required; use the one you have for now, but expect oil consumption and piston slap.


Looking up into the underside of the piston crown will tell if the issues was combustion temp relates or not?


Blackened with burnt oil? If so, you had combustion/timing related issues.


If the seizure has in any way wiped across the top-land area across the rings, as opposed to primarily the skirt area, the Top land dimension was too large - clearance too little.


If the scoring of the skirt area is '4 point' on either side of the thrust face the piston/bore clearance was too little.


A wiped-out/scored thrust face with no sign of over heating to the underside of the crown was case of too much too soon on the new rings and bore. (Owner inflicted)

The mods that you have made to the oiling return system have seen an increase of oil capacity of over 10%, plus a much greater oil contact surface area exposed to cooling. Your oil was running MUCH cooler than in a std motor.
Thus oil related over heating will not have been an issue or a contributing factor in the seizure.


Your perceived oil pump issue was not related in any way to the events around the seizure...