1984 80" Shovel. Noticing some smoke from the pipes like I'm burning a little oil. Checking top dead center, I notice some burned up black buildup (assuming oil) on the tip of the screwdriver when I'm checking the piston TDC.

With the smoke and buildup - assuming I need new piston rings?

Main question is - how difficult is a new piston ring job? I know it's pretty simple for the seasoned vets but this is my first "built" bike. I rebuilt the cam chest so I'd feel pretty confident getting into the cylinders etc. Only way to learn is do it yourself. Assuming the cylinder walls look good, would it be a plug & play for new pistons or do I have to get them honed regardless? Thanks.

 

You will always get a bit of buildup on the pistons, I reckon once you use a quart in less than a 1,000 miles you wanna pull the top end.

Always hone with new rings and check valve guides and replace the valve guide seals while the heads are off, lap the valve seats too.. It isn't that difficult if you pay attention.

 

I just don't have anything outside of a bike lift and a tool box of wrenches & sockets etc. No machines.

 

If you decide to pull it apart and refresh the rings. First find a good machine shop that specializes in HD motors. Take the pistons and cylinders to him to be measured and inspected. Chances are if there's appreciable wear, you may want to just bore the cylinders and use an oversize piston and rings. I would also have them inspect the heads since they would be off the motor.

Before I took it apart I would want to run a compression test for both cylinders. If for no other reason you know where you are, and also will see if the pressure is low. I would want to also run a leak down test. I realize you probably don't have the tools to do either, but maybe you can borrow from someone you know.

 

I've got a gauge to test compression. In what instance would I only need to replace the rings or would replacing the rings mean also replacing the pistons?

 

This is why you have the cylinder bores measured precisely and see if they're a cause of concern due to wear of the bore. They would also measure the pistons to try and determine if they're worn. They will know if just rings will solve any sealing issues.

Compression test is so you know where you are. Are they both equal, are they both measuring high enough? The leak down test can detect pressure loss at the rings, valves, and or head gasket. Shovel valve guides and valve stems don't have really high mileage life if they're still OEM parts, although later models were better materials. And the guides if worn can cause issues with oil being sucked into the combustion chamber. Keep in mind the motor is 40 years old.

 

K.I.S.S. . . . how many miles on the motor? Could just be bad valve guide seals . . . ? Check the simple things first before convincing yourself you need to rebuild the whole top end. Just my 2 cents.