I have a Honda HRX217HXA lawn more that is no more than 3 years old. This year, after having been stored in the garage for the winter, I started it up and noticed that it would not idle correctly. With out the blade engaged the RPM of the engine would increase and then decrease. After engaging the blade the idle would run smooth and normal. I thought that maybe there was something stuck in the carburetor so I took it apart and cleaned out all the jets with carburetor cleaner. I put it back together and it was still doing the same thing. I just lived with it for awhile. Once the weather got warmer I noticed that the problem went away. Now that things are starting to cool off the annoying problem has come back. I don't know if the temperature really had anything to do with it, but it coincided with the problem. I'm really stumped as to where I might need to try next to resolve the issue. I have the maintenance manual to assist, but it doesn't mention anyting on this issue. Please help!

most carburetor's have a small screw on the side, try adjusting this to increase or decrease idle