piston balancing

[Phil West]

I'm balancing my first set of pistons - I need to take off 3 grams.  I got the Fisher book but it's not very specific.  I'm thinking the wrist pin shoulders are a good place to start removing metal but it would be guesswork.  Can anyone suggest the best place to start grinding?  It may be easiest to use a clockface on this pic - so grinding the shoulders would be 3 oclock and 9 oclock.

Any help appreciated!

Phil 'The Drill'

[Peter]

I removed 6g like that
(below the wrist pin on the shoulders)
 No problem

[andy M.]

I'd go 10 & 8 and 2 & 4, leaves a bit of meat behind the pin,

andy

[m.m.p]

DO NOT TOUCH THE PISTON!!!!!!!!!!!

weigh the pistons only, without the gudgeon pins, make a note of each piston, then weigh each gudgeon pin and make a note of it, then match the pistons with the gudgeon pins to get a close match with the weights, then take the weight ONLY OUT OF THE GUDGEN PIN!!!!!!!!!, you take the material out of the inside of the pins at each end, that way you wont weeken anything and steel weighs more so only alittle is needed to be taken out.
 

[Phil West]

thanks guys.

Marco the wrist pins all came out the same weight  so can't get anything more out of switching them.  Anyway I wish I had a lathe to turn out the inside of the pins - I'll have a careful go on the pillar drill.

Anyone know what the square lump on the wrist pin boss at 3 oclock is?  I'm guessing some sort of casting effect so that square lump could be removed.

[andy M.]

the lump is to distinguish which way the piston goes in the bore, it's on the same side as the arrow on top

andy

[Bruce]

..., then weigh each gudgeon pin and make a note of it, then match the pistons with the gudgeon pins to get a close match with the weights, ....

There's no point in doing this because the wrist pins will always be identical in weight.  Every dimension is controlled.

Phil, if you're using teflon wrist pins, don't try to open up the ID of the pins.  You won't be able to drill them anyway, they are much harder than your drill bits.

You can remove some material from the underside of the crown of the piston where the name Mahle is cast in.  Take off the bump at 3 O'Clock.  Taper the ends of the two ribs by the skirts.

[Phil West]

Yep just tried drilling the wrist pins and no go against my drill bits!  Lump removed - now all within 1 gram.

Cheers