Has there ever been a 8–1 in MLS?

Yes, 1 time.

The only time: June 3, 1998, LA Galaxy beat FC Dallas (FC Dallas 1–8 LA Galaxy).

Nearby scores

1. 9–0 Never
2. 9–1 Never
3. 9–2 Never
4. 8–0 Never
5. 8–1 1 time
6. 8–2 Never
7. 7–0 6 times
8. 7–1 6 times
9. 7–2 3 times