I took my crank to be balanced at a local shop, they asked for the crank and the flywheel together. Two weeks later I came back and gave them $200 bucks. Went home and didn't see noticeable changes to the crank but I flipped over the back of the flywheel I see this. Should I be concerned?

 

The crankshaft should have been balanced by itself. Now, you are only balanced IF you bolt THAT flywheel to it... and it will have to be indexed for it to be correct.

 

Well we cant have that..

 

Agreed. You need to talk to the shop and figure out exactly what they did. If they balanced it as an assembly, it's not right. They should have balanced the crank, then attached the flywheel and balanced again.

Did they take a piston and rod assembly as well? Or at least ask you if you had the weights of one?

 

My shop does that sometimes. They balance the internal rotating assembly first, then they balance the clutch and flywheel. The clutch cover should be indexed to the flywheel and the flywheel should be indexed to the crank. They index them that way because that's how they balanced it, and that's 100% precision. But if you were to clock them differently you would still have less inbalance than if the clutch/flywheel was not balanced at all. They just made it extra perfect is all.

Don't worry, if you end up taking the clutch and flywheel and using it on another motor, it's not going to hurt. I've moved my balanced clutch/flywheel to 2 different motors and have seen no issue with bearing wear, and thats in lap racing environments where RPMs are generally higher.

The machine shop did you a solid by balancing the flywheel and clutch cover together IMO. It shouldn't ever hurt.

 

Sure. It makes sense to balance from the crank outward so every piece is balanced and the whole thing is also balanced as an assembly... But I've never seen a crank balanced without the reciprocating assembly to calculate out the bob weights though. Is that a thing? Maybe I'm just spoiled?