Misfire Module B

I decided to do some research as a troubleshooting tactic, rather than try to do additional hands on troubleshooting.  It is amazing what a log book can reveal.  Take a minute and follow the log book entries below.

Oct 2013  Ready to fly  (winter in Florida)

May 2014  25 hrs flown off

Oct 2017  300 hrs  Overhaul carbs with kits  (winter in Florida)

Apr 2018  330 hrs  New style float available.  Ordered and installed by dropping the float bowls only.  Did not                                      remove carbs or make adjustments  (Started feeling vibrations)

May 2019  380 hrs  Replaced junk exhaust system with new style

Oct 2019   425 hrs  Replaced exhaust system due to broken inlet pipe #3 cyl.

Mar 2020   426 hrs  Replace carb circlips per service bulletin.  Did not remove carbs.  Serviced from the top.

April 2020  435 hrs  Chasing serious misfire on Ignition B
                             Troubleshooted Electrical,  Pulled and examined #1 and #3 cylinders.
                              ! The Light Bulb Went Off !

It sure looks like all of my troubles actually started when the new floats were installed.  I am planning to send off both carbs to Lockwood for overhaul and re-assemble the engine in the mean time.

What do you think......................Tom

I would pull the floats and weigh them and check that the circlips are in the position where you think they are.

You might want to raise them one position leaner.

But this still does not explain the miss only on Ign B.

I just pulled and weighed the floats.  Even though I bought the new style and installed them in April 2018.  My old ones were original from 2013, and still within specs, but the  new style was said to be far superior.  So. here is the result:  Rt carb  3.9 & 3.5.  Lt carb:   3.80 & 5.8.  Not sure either why ignition B would be so much rougher than A, but it is obvious that the left carb was flooding. What I can't believe is that I had no fuel running out of the overflow tube, and no fuel on the carb tray.  I may have multiple problems, but carb overhauls will be first...Tom

In Hindsight: If it "Aint" Broke, Don't fix it!

The Float Valves may be slightly leaking,  causing a rich mixture; especially at idle.

Do you routinely Shut OFF the Fuel Valve between Flights?

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I am still requesting Discarded heavy floats for Testing and Experimentation.

Would you be willing to donate to the cause???