The Stovebolt Site Forums The Shop Area Engine Shop Basement balancing.

I bought this scale at a police auction for a few bucks, the previous owner is serving a little time away from home,lol.
These British Royal Enfield bike parts are quite consistant, only a a few tenths of a gram difference, but on my Stovebolts, the pistons and rods were many grams difference in weight.The crankshafts on inline engines are balanced seperately from the rods and pistons etc,and the local machine shop said the factory balancing on cranks is almost always good, it's the other parts that need balancing.Rods should be done one end at a time on a axle so the rod pivots and you trim the small or big end accordingly.Anyways it fun to do when you're bored, notice the bike crank in the photo, an inline engine
[img]http://img.villagephotos.com/p/2003-1/95040/LLLVH-scale.jpg[/img]

Tony, do the police enter auction buyers into their database for future followups? I wondered about that when I saw all the high pressure sodium light setups they were auctioning off here.

I don't know, just paid the money and left.I told them I was gonna weight motor cycle parts,they said "yeah right" and laughed.

Tony,
When doing final balancing of rods, pistons, wrist pin assys . . . the machine shop that I worked with took an end-mill that was just slightly larger than the wrist pin bore and went in on the ends of the pins to get the weights all within .1 grams for the assembled components.

The pistons were already within .1 grams of each other, but the rods varied a little (+/-0.5 grams) and there were no good places to machine that much material off -

When I did one of my 261 engines,the rods were off on the top end,so I made adjustments by taking the lightest rod on the small end ,and put the heaviest piston on that rod.The engine is very smooth, so I must have done something right.
British bikes all have forged aluminum rods, the big ends have a web on the cap you can grind on, but they are usually very close in weight.On the pistons I remove material on the wrist pin side.

Tony, I use the exact same triple-beam scale in the school shop, weight-matching rods, pistons, etc., prior to spin-balancing smallblock Chevy crankshafts. We match them to +/- 1/10 gram. Since a dollar bill weighs almost exactly a gram, that's pretty close! I've also got an old 2-pan beam-balance scale my father used to use on flathead Furd parts back in the late 40's, and it still works. I just have to find the lightest part with that one, and use it as a reference while I match the other pieces to it.

BTW, some of the race wrist pins I use come with instructions NOT to try to balance by machining the pin ends. If the pin is running against a lock ring in the piston boss, machining the hardened end surface away might result in premature wear. Be careful!
Jerry

So ... how much are you charging for a quarter-bag of good Jamaican?

Ha, isn't Indica the smoke of choice today?
Jerry, I used to balance the bike cranks on a set of parallel knife edges.The cranks were balanced with a factor of the total rod and piston weight,between 70-85 percent depending on the rpm range you run it. British 40-45 cubic inch twin cycle engines always vibrate,the trick is to put the vibration at a speed where you don't usually ride at.Vibration can be so bad it blurs your vision,now that can't be good.