[md8181]

bought an engine with 400 miles on it. How long should I go before first oil change??

 

[Mr645]

500-700 miles change oil and filter to clean out any debris left from assembly. After that 2500-3500 seems about the norm for a hard run motorcycle engine

 

[AyeKay]

Factory says to change oil at 600 Miles , then your next interval would be 4,000 miles.

 

[elitopus]

bought an engine with 400 miles on it. How long should I go before first oil change??

If i bought ANY used engine no matter what the miles the first thing i would do is change the oil. I assuming you got this on ebay or something?