:: ENGINE PROBLEM ::

The recommended honing allowance when re-boring is 0.05mm to 0.07mm.(002" to .0025"). The reason that this amount of honing is recommended is to ensure all the boring marks are removed. The boring process leaves a rough surface similar to milling and is very unsuitable as a surface for rings to run on. A shallow hone pattern will disguise these boring marks so they are not visible with the naked eye, resulting in pre-mature ring wear. After the rings have failed the boring bar marks can be very visible in the ring travel area, even though the hone pattern completely disguised it at the time. So 0.05mm to 0.07mm (.002" to .0025") is adequate as the honing margin provided the bore finish achieved is satisfactory in the first instance.
( The required boring bar finish normally can't be achieved in one large cut. A final bore cut depth of around .005", with a correctly sharpened tool will produce the recommended bore finish ready for honing).