1992 xp 580 wont start with gas and spark

[snark]

hi everyone. new to this site and have a starting problem with 1992 xp 580 white motor. motor is getting spark and gas but wont start. had it running last week but is was hard to start. plugs are wet with gas both plugs show nice spark, but will only studder once in a while and thats it. heard people talking about rotary valve problems and timing issues. new to working on this motor, so how can i check the rotary valve area without pulling the motor. thanks for your help.

 

[rickford]

The rotary valve is between the intake manifold and the engine. 4 bolts remove the manifold. The rotary valve is a half moon shaped piece of sheet metal that rides on a gear. It's not likely to go out of adjustment on its own because of how it is attached, but if you want to check it, here's how from someone else's thread. (I had exactly the same problem)
Take the spark plugs out. Turn the motor over by hand to TDC on the front cylinder. Find the 'cut' mark on the rotary valve housing below and to the front of the front intake port---the mark is just outside where the 'o' ring seals the housing...the valve disk is installed with the open side up and the front end lined up with the mark....
While you've got it apart you should probably clean the carbs.

 

[rickford]

I have exactly the same machine, that I bought for a song after it had sat for a couple of years. Taking the carbs apart and cleaning them did the trick. It was easier to take the intake manifold off first to get at the carbs and that's when my rotary valve fell off. I didn't even know it was there.