Aircam with 1 Rich Engine

Hi Mark,

A couple of items to check. First how old and how many hours on the engine? It isn't always just about hours, but time since the MFG date. Have the carbs ever been overhauled? Has anyone ever worked or tried to adjust the carbs ( i.e. maybe played with the needle clip position)  When was the last carb sync? When were the carb floats weighed last? Do you have EGT temps for each engine and what are they in comparison?

All great questions. I'll tick them off one at a time.

First how old and how many hours on the engine? It isn't always just about hours, but time since the MFG date.
-  270 hours on each. Big bores were added around 70 hours ago. Hal Stockman's. Intake cross over tube added to each engine at the same time as big bore kits.

Have the carbs ever been overhauled?
- Not since new

Has anyone ever worked or tried to adjust the carbs ( i.e. maybe played with the needle clip position) 
-  Adjustment made when Big Bore Kits installed.

When was the last carb sync?
-  Same answer as above.

When were the carb floats weighed last?
-  I don't think this has been done. 

Do you have EGT temps for each engine and what are they in comparison?
-  I do not, but that would be easy to do.

Thanks for your help with this. - Mark

Hi Mark,

Sorry for all the questions. Just trying to pinpoint the issue for you.

Did this start right after the big bore kit was installed or just a new issue? How old is the engine? 

Quote:

Has anyone ever worked or tried to adjust the carbs ( i.e. maybe played with the needle clip position) 
-  Adjustment made when Big Bore Kits installed.

What did they do to the carbs? 

Hello Mark

I would suggest you contact Aircam, I am aware that they have worked with big bore engines in the past.  They may have seen this before. You should verify the carb settings are equal on each engine first.  Changing settings to balance them I do not think is wise.  It may be prop blade settings between the 2 engines are not the same leading to the fuel imbalance.  I assume you run them at an equal RPM so perhaps it is load related.  

The suggestion to check the needle clip positions and weight the floats are valid also.  Verify that the mixture screw is set the same as well.  In the Rotax manual there is a requirement to inspect the carbs at 200 hours for signs of wear on the needles and jets, perhaps this would be the first thing to do as Roger suggested. 

Cheers

Did this start right after the big bore kit was installed or just a new issue?
-  I purchased the plane when the big bore kits were installed, so I don't know the answer to that. It could be the high altitude is not adjusted for the same for each carb?

How old is the engine? 
- 2019

Thanks for the suggestions. I'll be having a Rotax certified tech help me with the condition inspection, so I hope he's well versed with the carbs and adjustments needed. - Mark