When I hold the bar down that engages the blade it will not cut?

This is probably due to a misadjusted or faulty safety switch on the rider's seat. There is a deadman switch there that will shut down the mower if the rider gets off the seat with the blades engaged.

check fuel filter and pump pressure starving for gas

some have a manual off /on fuel control, some have a safety bar that you hold while running and the blade is engaged. I f you have the bar at the handle end and you do not engage the blade, and this still happens, check the cable from the handle to the engine and see if when you assembled the unit that the cable has been run properly.Ever year I remove the handle for winter storage and fold the cable and handle on top of mower, and not disconnect cables. In Alaska we get snow in winter and mower does not work well, a little humor. good luck..

Hi, you must have the blades disengaged and the park brake locked on before you can get off it. Regards Phil.

blades will only engage if you hold the blade lever forward and not in it's locked in place, why would this be?

Not familiar with this model, but a thought, check for a kill switch.

a lot of people have this problem with a chain saw and cant get a strate cut, most of the time its down to them trying to force the saw through the wood and in doing this the saw cuts around corners as there pull is not square to the cut,, let the saw do the work, not you, if your pulling on the saw to make it cut well then it has a very dull or blunt blade,,,is there any side to side "rock" on the chain in this new bar? how have you sharpend it? dose the chain have the same pitch on both side's? are all the teeth cutting at the same depth? if its cutting around corners it could still be the chain pitch worn out, if so the chain is past its best as well, but most of the time its all down to how hard and how squarely your pulling on the blade when cutting,,,the first thing in logging to lurn is to cut squarely no easy task that! just dont force the saw to cut!! it will cut just as fast or faster without forseing it,, if all this still dont get you cutting right change the chain for a new one,,,the only hard work with a chain saw is holding it up to the tree and humping it around not cutting with it, thats the blade's job to do so the faster you try to make it cut the more out of true the cut go's as all your doing is bending the bar out of alinement,,all in all, its two hands for the job and a very gentle pressure on the saw, start the cut with the blade spinning and dont stop the blade in the wood, cut right through

No you do not need to holde the lower blade guard up. It should be spring loaded and move upward as it engages to piece being cut. depending on what you are cutting, you may need to hold it up to start the cut, but then it can be let back down while cutting. It is a safety feature designed to keep as much of the blade covered as possible during use.

There is a possibility that the spring one of the ends of the cable attached to the bar you are holding has stretched causing you to have to grip it harder to make the mower work. First try taking the end loose from the bar and tying a knot in it to make it a bit shorter. This usually works, but you may have to replace the cable.

Is the belt on the pulleys ? If so your cable is broke its what engages deck belt