Re: Rough running around 5000 rpm
by Rotax-Owner » 12 months ago
Let's go back to basics when diagnosing the issue. When you're operating at that RPM, you're essentially drawing all your fuel through the main jet. We recommend performing the following checks:
If you upload a photo of your engine, we may be able to identify an issue (or potential issue)
If you don't feel comfortable or lack the appropriate tools to perform these tasks, it is recommended that you take your aircraft to a trained Rotax mechanic (iRMT) to assist with diagnosing and resolving the issue. To locate an iRMT in your vicinity, you can click on these two links:
https://dealerlocator.flyrotax.com/
https://www.rotax-owner.com/en/support-topmenu/find-service/rotax-irmt-service
Re: Rough running around 5000 rpm
by Jeffry Stetson » 12 months ago
You don't state airframe, age, etc. which may play a role. I had similar symptoms, getting progressively worse over 2 years, due to an air leak through the stem of the fuel tank selector valve. Some of my other posts discuss this in greater detail.
Re: Rough running around 5000 rpm
by Rotax Wizard » 12 months ago
Hello Jeffry
Can you tell us if you are getting the RPM by throttle setting or load of the propeller with your Airmaster? The major item that changes over time is your gearbox will wear in and reduce the tension internally. If this is too low at peak torque areas, 5000 to 5200, it can start to move in the overload clutch with bounce from the reduced tension preload.
One simple check would be when the engine is warm on the ground at idle, 1400 to 1600 RPM for example, is it making a rattling noise? If it is then fix the shimming of the gearbox and try it again. It is not uncommon to see issues, especially on reducing power from high RPM to cruise, to get a vibration at the peak torque settings on a worn gearbox.
Given that the engine is in mid range of the carburetor settings perhaps see that the jet needle is not vibrating in the needle jet. Check the circlip position as well. The factory setting is number 3 groove but in hot weather number 2 might be better. it is always good to sync the carbs and ensure that the midrange is running balanced. (mid to full open is the most important)
Let us know what you find.
Cheers
Re: Rough running around 5000 rpm
by John Kirkegaard » 12 months ago
The status of today:
I have checked the bowl- no contamination
Have not checked the main jet yet - during take off and climb with the highest fuel flow I have no misfire issues.
Checked the floats: 3.0 to 3.1 grams each and no damages.
Filter/gascolator are absolutely clean.
Drop test: drops 75 rpm for both positions.
Have not checked the resistance and pin connectors.
Carbs are balanced.
Propeller not balanced.
Purchased 2 new ignition units, but not installed them yet (received them last Friday).
Checked the situation yesterday: I did make a climb with about 90 kts. The temp held on 90 degree C and there were no issue after levelling out.
Seems to be more prone to make the small 'ticks' when the engine temp is above 110 degree, so now I hope that installing new ignition units and install them away from the motor may help :-)
Re: Rough running around 5000 rpm
by Rotax Wizard » 12 months ago
Hi John
Consider this. The engine runs on 2 ignitions. Just change one and try it. Even if one completely fails it should run fine. The problem you describe would require 2 plugs in the same cylinder to stop intermittently over and over. Each head has one plug on A and one plug on B side. This type of failure is highly unlikely in my opinion. I don't know if you have carb heat but if you do try turning it on when this happens. (it will enrich the mixture) it may help you diagnose the issue.
Cheers
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