912 to lean at WOT

[bbs428]

Need some guidance on jetting my carbs. During testing the AFR gauge hit into the high 15’s
Im not sure what I’ll need other than some higher numbered main jets. I’m guessing a float boat gasket and ??

Any help on where to purchase and the basic procedure would be appreciated, Thanks!

[avidflyer]

If you have high egts at full throttle, then the main jets. Usually the float bowl gasket stays up in it's groove in the carb body, and there is no need to replace it. If it drops out, just be careful not to tear it. Needle height controls egts at mid range rpm. JImChuk

[bbs428]

Thanks
High egts are at wot at 5.8k rpm
midrange is fine

[avidflyer]

Might think about a bit more pitch in the prop to lower maximum rpm a bit? JImChuk

[Delta Whisky]

Brett - you might want to check the float level, carb needle "C" clip location, and fuel flow/pressure (if you didn't as part of your review with your DAR) before going with a larger jet. Any or all of these potential culprits could cause your issue and they don't cost anything to check.

[bbs428]

Idle and midrange are good. AFR is 13.5. A little rich but ok.
AFR is reading 14.2 @ 5.4k rpm level flight. About perfect.
At 5.8k rpm AFR starts approaching 15. Lean
If you initiate a climb at wot, AFR goes to 16. Very lean.

The AFR gauge is a real great troubleshooter. I initially had 15-16 at 5.4k rpm straight and level. Landed and cooled off. We then checked the spark plugs. Pilot side were white. Passenger side were tan.
Removed pilot side float bowl and main jet. Was a little dirty. Jet had some crud in it
Cleaned and reinstalled. Removed passenger side float bowl. Not as bad but cleaned bowl and main jet anyway.

More troubleshooting today.

[bbs428]

Fixed!
Reamed the main jets from .075 to .061 in three increments.
Final AFR @5.8k is 13.8 to 14.2 and at 5.5k it’s 13.6 to 13.9

Quote from Manfred - “climbs like a monkey and maneuvers like the devil!”
😁

[Eric Page]

Reamed the main jets from .075 to .061...
You have a reamer that makes holes smaller!?!? You should corner the market -- you'll make a killing! ;)

[bbs428]

.058 to .061 😁

[trond]

well done. But you are still running on the lean side at WOT 5800 I think 13.5 or so should be target. Not above 14. But clearly you have done good progress in the right direction. I was unable to fix it myself until I went EFI and not for lack of trying. At least you have moved in the right direction. Well done your engine will thank you