gearing options for dr 350?

[Krs1 0]

Hello all, i have looked for this subject and im sure its out there but couldnt find it. i wanna know how many teeth my stock sprockets have. i believe 14/43 but not sure. i want to get more out of my low end so i placed a 13 on the front with a small amount of change. my questions are if stock is 43 sould 45 make it to low and if i did go 45 would the stock length chain fit with the 13 in the front? btw its a 1990 dr 350s. thanks in advance!!!!!!