Dryer will not start. About 4-5 years old. Electric motor sounded a little weak when running the past few months. Heating seemed fine and heat vent is clean. What is cost of new electric motor?

Most likely motor is bad. It runs a little while,overheats, and shuts off. After cooling down it will restart and repeats process.

I assume you mean the clothes are not drying as well or as quickly as they use to.? If so I would start with the Vent system ,85% of extended dry times are vent issues. Start by running the unit and going outside to the dryer vent and check for a good flow of warm air,if very little air is coming out of the vent you need to clean or have the entire exhaust system cleaned out.. With out good airflow you will just end up with warm moist clothing the airflow helps remove the moisture.. If not a airflow problem it may have a thermostat issue not letting it get hot enough or not staying hot long enough,,Hope this helps GOOD LUCK

So,. basically your drum doesnt turn. SO your getting heat still even though the drum isnt turning. Is this right? Sounds strange??? Do you hear any humming noise when you push the start button? I need to know a little more about the problem because im kinda confused as how you decribed the problem. Iv never seen a dryer heat but the drum not spinning. especially your model dryer. Its electric heat right? because if the drum doesnt spin, maybe your motor is bad. and if your motor is bad, then your heating element wont heat up because the centrifical switch in the motor is not switching to complete the circuit to the heating element. So this is why im confused when you said" Dryer heats when knob turned but when "push button" pressed, drum doesnt run." Because your belt wraps around the motor pully and the motor is what makes the drum turn. Like i said, i never seen this model dryer heat with out the motor operating. So if you can give me some more info, ill do my best to help you out....Thanks!!!!

Ticking sound is the timer running--so it is not the problem unless a contact has failed or a wire has come loose.  Broken door switch, thermostat failed in open position, or clogged lint filter/exhaust vent/outlet would keep unit from running.  If you can hear the motor running but the drum is not turning then the drum belt is broken.

1. unplug your machine and rach as far in the exhaust part of the dryer to see if there is an obstrucxtion. 
2.Take out the lint filter and make sure there are no gaping holes in the screen
3. Check the exhaust house leaving the machine or blockage, this hose should not run more than ten feet for optimal drying time.
4. its your heating element

sounds like you have weak coils. I have had this many times in the past and changing the coils has always seemed to work....they work fine when they are cool, but once they heat up they stop working.

if the motor buzzes when you push start then it is a bad motor.as long as the drum turns freely by hand.

remove the vent on the dryer that goes to the outside start the dryer if it continues to ru n and not cut off you have a venting problem of the house

if it cuts off after 5 mins with the vent off you have a motor that is going bad

Replace the motor .

the dryer is not the problem the problem is the house vent it is restricted some where