[Jay S]

For HR lifters generally a full synthetic or a multi grade 10w50 or a 15w50 parasynthetic will work better over a conventional 20w50. Harley’s use HLJ “SE” with 20w50 oil, but the oil operates closer to 300*. They start out cold just like anything else. 10w30 is what is recommended for most automotive HLJ slow bleed HR applications.

For thicker oil most HR valving is to restrictive when cold and they may make more racket until they warm up. If the noise doesn’t quiet down with 20w50 I’d just try a different oil or viscosity. Morel’s are one of the worst lifters with thick oil, the feed to the plunger can even be to restrictive even after it is hot. Dropping back on the viscosity usually helps quiet’s them up.