Assembly lube—to use, or not to use, that is the question. Well, before I bark at you to do something or not bother with it, let's look at what assembly lube is designed for.
Assembly lube is meant to be used while you are doing engine work, in our case we are installing a new cam in our 2018 Harley-Davidson Street Bob. The primary goal of said lube is to prevent metal-on-metal contact during the initial startup after engine work.
Personally, I have always used Screamin’ Eagle’s Assembly Lube when doing motor work on H-D models, but my local Harley dealership persuaded me to try out a lube from Maxima. Both are about the same price: Screamin’ Eagle’s coming in at $11, and Maxima’s at $10. The only difference I noticed between the two was that the lube from Screamin’ Eagle was a much higher viscosity. That being said, I noticed no difference in application or performance.
The main thing here is that some type of assembly lube should absolutely be used on bearings, cam lobes, bearing surfaces, tappet wheels, as well as pushrod ends while doing a cam swap. Another little piece of advice when doing a cam upgrade is once everything is back together run the starter (with spark plug wires disconnected) half a dozen times or so to build your oil pressure back up. (Be sure to take breaks so you don’t overheat the starter.)