There can be other factors at play here that you aren't considering. You could have air leaks at the base gasket or your crank seals.
If you used the included base gasket with the kit, they are often undersized and can block airflow.
Typically, a run of the mill tomos 44 or 45mm kit will want in the low 70's for jetting on a stock intake with the 14/12sha. 61 is way too low.
Let's have a look at the spark plug?