Balancing Con Rods & Caps

I'm starting to reassemble the bottom end on my '69 S model. There was a nick in one of the rods where a piece of stellite had gotten loose from a tappet many years ago before I got the bike. I filed that rod a bit and then balanced it with the other one. However, when I weighed the caps there was about a 10 gram difference. I'm curious as to whether this is enough to warrant trying to get balance the caps or if I should leave well-enough alone. Thanks for the input.

Nelson

Was the nick in the rod or the cap,10gr. is alot,a big nick in a40year old rod thats probably due for replacement any way?Rods are balanced from each end and not overall,as the bottom end of the rod is rotating weight&the topend is reciprocating weight,along with piston,rings ,pin ect.Someone who took pride in their work would try for 1/2gr someone who couldn't give a #*%$ would take them off you,charge $100 and give them back to you and you would be none the wiser.

I had Chip's rods & pistons weighing in within .2 oz of each other. I didn't attempt to measure each end of the rods, though; I'm sure they were WAY close.

Was the nick in the rod or the cap,10gr. is alot,a big nick in a40year old rod thats probably due for replacement any way

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Investing in a new set of rods may not be a bad idea. 10 grams seems like A LOT! I just weighed a stock cap and it weighed 135 gr. so what percent is 10 grams? You could be working with a mis-matched set as in someone replaced one con rod once already. Can you see a difference between them?

I just checked one set I had loose here that have been previously polished and balanced and they are within 1/3 gram measuring:
each rod
each end cap
each assembled pair

I'm not set up to measure the rod ends individually.

Comparing a stock cap at 135 gr. vs the balanced caps that weigh 129gr. I'd think you could still shave 4 grams off them so theoretically you could balance yours (remove 10 grams from a cap) but only after doing the rod ends comparison 1st. so you know you're not moving in the wrong direction. Sorry, I don't have 2 stock rods and caps to compare to try to see what was permissible from the factory (and I sure don't remember). How do your pistons compare? What compression will it be?

Are you sure there's not a shell still stuck in that cap?

Are you sure there's not a shell still stuck in that cap? [/quote]thats a good call or a nut missing.Aluminium rods aren't really suitable to remove 10gr off,unless you cut the smallend boss off,only remove weight from between the ribs on the cap.I personally hate aluminium rods with steel caps, :twisted:

The nick was in a rod. It polished out fairly easily. The caps looks bone stock but one is 145 grams and the other is 155. There is a little difference in the factory grinding on the ends, but it sure doesn't look like 10 grams worth.

Nelson

I used to balance each rod and piston as an assembly and when I had them to 1/2 gram I took them to the balancing guy with the crank and bearings. This worked very well for me on Nortons. I used to find rods and caps that were pretty close to start with, but this was many years back.
That's kind of a scarey difference to me.

Since both rods and caps rotate together, what difference except a left right rocking couple which could be corrected by the engine balancer? I don't think the factory ever matched all the parts that closely. I once saw an old film from Triumph and they used stock weights and only balanced the crank on a pair of knife edges.

I know something worth doing is worth doing well, so may as well do it right and channel some of our paranoia in metal

Jean

would you balance a car wheel from one side only?,same principal applies with the crank.