U.M.R. Engines

PISTON - PICKED UP

Pistons have 3 main types of skirt pick up or scuffing.

Centre skirt scuffing as the name suggest is usually more prominent on the centre of the thrust skirt of the piston.

The cause is a break down of the lubricant due to a number of possible reasons. These reasons include cooling system failure, lack of lubrication (check con rod squirt holes, excess conrod side clearance, dry assembly) and if the engine fails during running in it could be possible insufficient piston to bore clearance.

Four point scuffing can have a few causes but the most common cause is insufficient piston to bore clearance after rebuild. If the engine has run for many thousands of kilometres and is well out of the run in period the clearance may not be the cause.

Engines running with minimum excepted clearance may experience this failure due to a change in operating temperature, fuel mixture or ignition timing.

In most circumstances this condition is due to insufficient clearance. Under certain conditions it is advisable to increase the clearance by .025m.m.(-001 inch)

All over skirt scuffing has all the same causes as piston / seized (visit piston /seized for more details)

Disclaimer agreement

: Every care has been taken in writing this information and procedures, but no responsibility can be excepted for errors, omissions or misuse of this information and procedures. The information available on this site is for your instruction only and cannot be copied for sale, © copyright 2001 UMR Engines www.engineproblem.com.au