a friend has a 1982 sportster and just had a complete motor rebuild and is planning to use 10/40 wt. dino oil for the first 50 mile break-in....just wondering if that's too light???
right off I would ask the motor builder his recommendation.
(warrantee and all that)
any oil should be ok, especially if going to change it after only 50 miles.
has the engine been heat cycled and checked over?
I been running 60 wt straight oil in mine for 40 years.
your mileage could vary.
When I had my 1980 thousand CC engine rebuilt I used 60 weight. That's mostly because the oil tank didn't even hold 2 and a half quarts and it was summer time. Now that it has been broken in and the new home-made oil tank holds over 2 and a half quarts I run 20-50 because that is the grade Tripps Harley Davidson says is used in this area. Whilst I was stationed in Hawaii most of the riders used sixty weight and an in line oil cooler.