Hi,
I have relocated my airplane with a Rotax 912ULS from Panama in Central America to Victoria British Columbia. The climate is quite different here and the engine isn't especially happy with it.
So far I have:
1. Changed the oil
2. Replaced plugs. It was running Denso IXU24 5309 which is popular in Latam, I reverted to the Rotax-specified NGK DCPR8E 4339.
3. Checked carb floats. All 4 are of the new type and are floating well.
4. Inspected carb diaphragms. I found that there was some aluminum corrosion on one carb cap which had contaminated the diaphragm. I gently cleaned it off and replaced the diaphragm with a new one. I aligned both diaphragms correctly with the indents.
5. Balanced the carbs.
Behavior:
- It's running and producing good power but it's not as smooth as it was before at low RPMs (2200)
- It stumbles a little on the way to 4000 during the run-up when oil just above 50 degrees. When warmer it seems better but not perfect.
- Mag testing shows drops on each of about 600 rpm, but consistent between the two. Is 600 rpm too much?
- During cruise, on occasion you can feel a very subtle shudder for about 1/2 of a second.
- At 4800 RPM and above it behaves well. Below 4800 and especially around 4200 it runs a bit rough. Not dangerous feeling but not confidence-inspiring either.
Questions:
1. I watched the video about setting the pins for the carbs. Does the setting here need to be changed? Effectively I was at a higher density altitude before (35C @ sea level to 22C @ sea level) so maybe the engine needs to run richer?
2. Could this be indicative of a fuel system issue? I'm getting good fuel pressure, with only mechanical enabled and also with both mechanical and electric pumps. The fuel filter is a bit of a pain to get to.
3. What about carburetor air filters? Would cleaning these make any difference?
4. Any other ideas?
I did my iRMT maintenance course a few years back so I'm pretty familiar with the engine, but this situation has gotten the better of my (limited) knowledge.
Thanks
Matt
