1981 sportfire 440 low idle

[Oliver550]

My 1981 440 sportfire has been sitting for a year before I bought it. When i first start it, it idles and runs ok. After it warms up it idles low(around 1500) and surges up and down 300 rpm. I have replaced the fuel filters and gas lines and gas. I have cleaned the carb and put the airbox back on it. I have tried to adjust the small air screw and the larger idle screw. It doesnt make any difference when i do this. I can actually turn the idle screw all the way in and nothing. All adjustments where made with the airbox on and the motor warmed up. I tried to spray wd 40 around the carb boot and crank seals to check for leaks and no difference. Any suggestions would be greatly appreciated
Thanks

[AirborneX4Special]

Sounds a lot like that engine needs resealing. I'd find out if the previous owner knows when it was sealed so you don't have to reseal after you've changed pistons.

[Oliver550]

Unfortunately the previous owner has no idea. So should i do a compression test or just reseal with a new gasket set?

[AirborneX4Special]

When in doubt, change the seals.

[Oliver550]

There is a hole in the flange where the exhaust goes over the y pipe. Could this be causing me troubles?

[AirborneX4Special]

You mean the ball joint where the muffler attaches to the y pipe with a spring on each side? That would only make the sled louder if the ball joint was leaking. Be safe and reseal the engine.

[Oliver550]

Ok. When i real seal do i need to do rings pistons ect or just all the gaskets and seals?

[AirborneX4Special]

Gaskets and seals. Pull the engine and literally flip it upside down. If the crankcase separates without much trouble, which it typically does, change the crank seals and reseal the case with Yamabond or Threebond. If nothing else is amiss other than crank seals, you shouldn't have to tear anything else apart. Just make sure the case is clean prior to reassembly and poke around on the site for details on this work. Enough people have done this so there's bound to be lots of help. It's a safe bet you're going to find at least one faulty crankcase seal when you tear it apart.

[Oliver550]

Great. Thanks very much for the reply.

[Oliver550]

Ok. I was able to get get the engine clean. Installed new seals and have reassembled it. Another amateur question here. Which way is the exhaust manifold supposed to go? With long solid bar on the bottom or top ? Thanks