914 won't go above 3500 RPM
Hello everyone,
This was my first time doing the carburetor seals on a Rotax so I followed the Rotax-owner video series on the seal replacement, reinstallation, and synchronization without much trouble. However, when I do a run up, I can no longer get the plane (Rans S-7) to go above about 3500 RPM. It idles great until about 17% throttle, then RPM stops increasing, engine gets rough, EGTs plummet, and it looks like the engine is going lean of peak, all the way to WOT. No black smoke, manifold pressure gets up to about 27 so I am getting some boost and I have verified wastegate is operational. I pulled the carbs back off and checked the jets for blockages and went back through the videos to make sure I didn't miss something but I have the same results. I have checked everything that myself and other Rotax-familiar mechanics can think of in the system, but here are some of the general steps I've taken:
-Verified throttle rigging/operation and butterfly valve opens fully
-Verified choke rigging and operation
-Verified diaphragm condition/alignment and slide/needle condition/alignment
-Verified float bowls are not overtorqued and seated correctly. I have no fuel leaks at the bowls
-Verified both carbs have 1-1/2 turns on idle mixing screws
-Verified mechanical and pneumatic carb sync. Engine runs very smooth at idle
-Recalibrated throttle position sensor and monitored with engine running; throttle is reaching 112%
-Verified fuel flow/volume to carbs with both pumps (fuel filter was cleaned as well)
-Verified manifold lines are not kinked or leaking
-Spark plugs are new and verified ignition boot condition and tightness. Mag drops are well within tolerance where I can test them around 3500
Another weird thing I have seen is if you pull back on the throttle cable for the 1-3 carb above 17% throttle, the engine smooths out and RPM increases a few hundred which is the opposite of how the 2-4 cable reacts and how I would expect it to react. I am open to any suggestions at this point! It seems like it is a fuel supply issue and since I messed with the carbs and very little else, I have to believe the problem lies in how I put them back together. Thanks all!
