ST 4500 Issues
 

Bax , i have Read from a post on RCSB That there is a problem with a pin in the upper piston area that comes lose and scores the piston , also the oil hole in the big end may not be positioned right . any truth to these?

RE: ST 4500 Issues
 

We have no idea what you are asking about. There have been rare failures of the piston pin retainers, but that doesn't cause the wrist pin to grind against the cylinder liner. When a retainer fails, it is the part that causes damage. But again, it's a very rare happening.

We've never heard of connecting rod problems.

RE: ST 4500 Issues
 

its most likely from someone who didnt break their engine in right

I have recently heard from two internet comments about the wristpin circlip breaking on the large Super Tigres and scoring the cylinder liner. Any comments about this in addition to what has already been said?

It has happened, but it's not at all a common problem.

Many have commented about ST G4500 circlip failures, damaging the piston and cylinder. They have decided that breaking off the 90 degree tab on the clip is the solution. This should not be necessary. The primary cause of the failure appears to be among engines whereby the factory installed the clip with the tab horizontal, perpendicular to the piston travel, which is WRONG! It should be installed with the tab vertical, inline with the piston travel.

Apparently not all G4500 clips have been installed this way and why all engines do not experience this problem. The tab should be in the vertical position, either up or down, inline with the piston travel, as stated above.

I have found on my own NIB ST G4500, the clip was installed with the tab horizontal. The reason for the failures is primarily due to the flexing of the tab as the piston stops and reverses direction at TDC and BDC. The piston has significant insertia and each time it stops and changes direction, the circlip tab will flex. At the maximum recommended 8,000 rpm, that equals 16,000 times the tab will flex "per minute". It doesn't take long for the steel wire clip to fatigue and the tab breaking off, damaging your engine.

With the tab facing up or down in the "vertical" position, the flex is minimized, if not completely eliminated.

Remove your piston and check how the clip was inserted and if wrong, correct it. This just might save your engine!

Regards....