Throttle stiff after changing carburetor

Test flew my Dad's 150 hp super cub with a new Marvel Shebler Carb, which was what was on before, and noticed the throttle is very stiff. I also noticed some slippage during the flight-- idle drifted up to 1200 RPMs. Wondering if the stiffness is related to the slippage. Any suggestions in terms of ensuring smooth throttle operation would be appreciated. Thanks.

Have you tried installing the old carburetor and see if the problem goes away?

I believe my mechanic may have sent it in for the refund on the core (it was a rebuilt carb that we installed).

check cable routing. Pop the linkage loose at the carb and see if the arm works freely and if the cable works freely with it disconnected.

How did the "mechanic" return it to service if it wasn't right?

I recently swapped an engine on a Super Cub I rebuilt last year. Installed the engine at the owners airport and flew it to mine (55 miles). When I pulled the throttle back to land I could not advance it. Landed and could not advance it on the ground to taxi. Shut the engine down and it worked perfectly, started engine and it got very stiff but I was able to taxi to my hangar. It worked great on the ground but got stiff when the engine was running and seemed to get worse after a long flight. Work fine until I pulled it back to idle. Changed the angle of the throttle arm, repositioned cable clamp non engine mount, mark the cable to check for slipping and ended up not fastening the throttle cable to the center of firewall like Piper had done originally to make it work. Still stiffer than we like at the lower throttle settings and creeps real bad in cruise. I ordered a new cable and we will see. 1700 hours on the cable from 1982, tried lubing it.

Hi Steve, I appreciate that information and the photo. It looks like you are using the first hole in the throttle arm on the carb-- with the install, I noticed ours is connected to the middle hole and it almost seems like there is too much throttle travel. Of course, moving to the nearer hole might make the throttle even stiffer because you have less mechanical advantage. The cable seems to have slipped-- during the initial test flight it was stiff, but normal RPMs. During the second flight, I did takeoff and landing practice and the idle RPMs kept creeping up every time I landed. Instinctively, it seems like the stiffness and the slippage are connected. For what it is worth, during this same annual, we also replaced the engine mount, oil cooler, air filter, etc. Here are 2 pictures. The second photo was after the second flight.

I notice that some throttle cable/carburetor pictures seem to show the throttle cable attached to the lever through a bushing instead of a direct connection. I would have to go out to the airport to check, but I think ours may be installed directly to the lever (see photo above). I wonder if that is the source of excess friction?

Piper used a bushing to put the throttle connection outboard a ways. Univair has thse parts per the drawing. I have never been able to get full throw in any position except the first throttle arm hole. Who rebuilt your carburetor? Is there a chance that your cable is slipping on the clamp?

I think that it probably is slipping on the clamp. Maybe foregoing that bushing might also be a contributing factor.