Alright...I've thoroughly checked for intake leaks and have found none. I took everything apart (manifold off) towards the end of the mowing season just to have a better look at the intake, check for cracks, etc...found nothing and put it back together. It ran a little better (maybe?) but it was...
The gaskets between the carb/spacer/manifold are all new and seem to be sealing properly.
I'll check the manifold itself more thoroughly and report back.
Thanks!
I have a 98 MTD 800-series garden tractor with the 18.5 opposed I/C twin. (4-screw pump, non-adjustable carb).
Here's what it does:
1) Takes a LOT of cranking to start when cold. When warm, fires up with barely a touch of the key.
2) Surges at full throttle. Give it a slight amount of choke...