I have a 2004 dyna low, with 95 “ screaming eagle, and I rode it Sunday, it ran fine. That eve, I did a little pre maintenance, pulled and inspected plugs, cleaned and re-installed plugs, checked oil. well, today it ran like crapola, backfiring constantly.it’s like this I grew up in a automatic transmission shop for cars...but I know so little about bikes. I don’t even know how to check the timing! please help...