Light dimming when starting, you should test the circuits voltage you are using at the instant of start, if the voltage falls below about about 100 volts and or if it is less that about 110 when running BOTH motors the circuit is really not up to using for this washer. This washer had two strong but very inefficient motors [ by today's standards ] and it needed a good strong appliance circuit for best performance. As Andy suggested you could probably add a motor start capacitor on each motor or the motor that gives you the bigger problem which might slightly help but as long as the motors start quickly each time it really will not help anything either.

You likely have a bad diverter valve.

Welcome to the world of manually operated clothes washing and while I have several of this type of washer in our collection I would never find the time to actually do my laundry in one of these machines, LOL. When I was working MT in the early 1970s we sold a few of these washers, but when WP introduced their compact fully automatic portable in late 1972 we never sold another of the A50s, in fact we almost had to give away the A50 demonstrator that was on the showroom floor. I dough that MT sold many of these washers which makes them a must have for serious MT collectors. I also suspect that MT lost money on these as not only were they quickly beat in sales by many Japanese machines and as I already mentioned just as had already happened with wringer washer sales more than a decade before when almost all consumers rushed to fully automatic washers.

As a result most of the A50s saw little use and the ones that did suffered lots of early failures. Almost every Maytag appliance ever introduced since World War Two through there demise in 2006 had lots of problems that MT would correct over the next few years of production. This was one of the few products that they only made a few improvements in as I think they knew almost from the beginning it was not going to be successful in the long run.