The throttle on 92 breakaway is very hard to push. Any suggestions on where to start trouble shooting?

Back in my busnut days this was a common problem. The throttle cables got rusty/dirty. Sometimes you could pull them out and oil, but may gave up and put in air throttles.

Might be as simple as someone put in an oversize return spring.

I have no intentions of getting rid of this coach so I would like to fix it properly. Can these cable assys. be found? If not how involved is it to switch to air and where would I find such a conversion?

I think the first thing you should do is to find out if it is the cable or the foot peddle. It isn't too difficult to pull the pin at the peddle assembly below the floor board and then see if the peddle moves freely.

Check the cable end to make sure the rubber boot that keeps all the junk out is still good.

Also check around the peddle assembly top side for any signs of blockage due to stuff falling off your foot.

Check at the engine to insure that all the heim joints and throttle mechanism is free and moves easily. You can move the linkage at the engine without removing the cable.

If it is indeed the cable it may need lubrication or need replacement because it is starting to fray inside the jacket.

I lubricated my cable by taking it off at the engine side and then found a one foot long hose just large enough to clamp around the jacket. I filled the hose with oil and then forced it into the cable assembly with air pressure. I continued to do this until oil came out of the cable jacket by the foot peddle.

Be careful not to use any sort of grease unless it is very diluted as the cable will not move well with a lot of grease restricting the movement. (don't ask me how I know)

I think the cable is still available from Spartan but it will probably be expensive and will be a big job to replace.

Good luck.

I have replaced both throttle cables and shifter cables on my cruiser as well as a friends. Detached the cables feel free but with a new cable in place the difference was so great I thought it had disconnected. Lubricating generally is short lived since the problem is the liner in the cable.
The convention for the boat cables,and I see no reason for it not to carry over to all other applications, is for the length to be imprinted on the controlling end of the cable, the one nearest the pedal. That imprint will be inches of length. There are several manufacturers and prices, probably not quality, vary. Expect around one Barth unit, which this year, for me, seems to be about 0.10 boat units.
Good luck