IH 240-U Carb Problems

I am assuming you have an aluminum carb as the older Zenith's were cast iron(which I generally prefer as they held up better) With the aluminum carbs I usually find corrosion(a white powder from oxidation) inside and in the jet passage ways. Mostly found on carbs which have set in barns for too many years without being run. I have found the easiest way to clean away the corrosion is to remove all jets and bead-blast. Carb cleaner will not remove the corrosion. Just make sure the passageways are cleaned of the blasting residue with mulitple rinses( I find paint thinner works well and will help remove any oily residue and varnish along with blasting dust. If after you have cleaned the carb and you still do not get gas to your plugs there are several possible problems with either the fuel supply end or on the dispersal end I.E. out of tune intake valves(will not suck gas/fuel mix into the chamber.

Thanks for the information. I will pullit off and get my bead blaster fired up. I did notice (and forgot to mention) that apparently someone had tried to rebuild this unit before. I'm not sure if it is a jet or seat, but one of the brass pieces in the bottom of the carb going off at a slight angle, has been beat up pretty badly. I didn't try to remove it, thinking that since it had been running, this particular piece would be ok. I didn't want to shear or break something I couldn't replace. Was this the correct approach?

If this is inside the bowl at the bottom and has a hex head then it is a power jet which measures the amount of gas going into the main jet. I'm betting that someone stripped the threads in the carb bowl which is common in pot metal carbs. As long as you can get into the main jet passageway under the bowl to clean it out it shoulld be alright to leave this piece alone. However it is imperative to get into all passageways to insure complete cleaning. Use your best judgement.