Mike Buettgenbach
Active Member
The airplane ran great, started within about 1 second of hitting the switch.
Then, I began flying many cross countries, like 4 hrs/wkend for about 6-7 wkends, so a lot of constant power, constant altitude/attitude flying.
During this time, the motor became more and more difficult to start until one day in Branson, I had to crank quite a bit to get it started, . . . and it finally did.
So, after researching various forums and threads, I went for the easy answer; I regap'd the plugs to a smaller gap. No real change in start performance.
Then I went to carbs. Right carb (cylinder 1/3) looked perfect, no dirt, corrosion, just fine.
The left carb (cyl 2/4) was a different matter. Upon removing the dome cap, there was an obvious black powder in the dome (all other aspects were pretty normal). It appeared to come up thru the 2 small holes in the bottom the piston (didn't appear to be any other path for it to enter). The black powder was very fine in texture and somewhat sticky, resulting in the movement of the carb piston being difficult and "sticky".
Related item:
I have noticed a bit of an exhaust leak on one of the muffler inputs (gotta fix that) which results in a bit of black soot showing up on the lower rt side of the cowl where it meets the fwd fuselage. I only see this after these cross country flights.
Conclusion (or conjecture)
I'm leaking a bit of exhaust within the cowl (fact). The flying conditions cause the exhaust gas to be "re circulated" somewhat within the cowl, and are being injested by the left carb (more than the right carb due to bizzare airflow within the cowl). The miniscule particles within the exhaust gas are migrating thru the air fliter, into the carb, up into the air chamber and over time . . . shazam . . . I have a problem.
So, asking the experience guys; is this a practical explanation for my "black powder" in the carb air chamber?
Anybody else seen something similar?
Oh, BTW, haven't completed reassembly just yet, don't know if it fixed the start problem.
Thx much for your comments.
Then, I began flying many cross countries, like 4 hrs/wkend for about 6-7 wkends, so a lot of constant power, constant altitude/attitude flying.
During this time, the motor became more and more difficult to start until one day in Branson, I had to crank quite a bit to get it started, . . . and it finally did.
So, after researching various forums and threads, I went for the easy answer; I regap'd the plugs to a smaller gap. No real change in start performance.
Then I went to carbs. Right carb (cylinder 1/3) looked perfect, no dirt, corrosion, just fine.
The left carb (cyl 2/4) was a different matter. Upon removing the dome cap, there was an obvious black powder in the dome (all other aspects were pretty normal). It appeared to come up thru the 2 small holes in the bottom the piston (didn't appear to be any other path for it to enter). The black powder was very fine in texture and somewhat sticky, resulting in the movement of the carb piston being difficult and "sticky".
Related item:
I have noticed a bit of an exhaust leak on one of the muffler inputs (gotta fix that) which results in a bit of black soot showing up on the lower rt side of the cowl where it meets the fwd fuselage. I only see this after these cross country flights.
Conclusion (or conjecture)
I'm leaking a bit of exhaust within the cowl (fact). The flying conditions cause the exhaust gas to be "re circulated" somewhat within the cowl, and are being injested by the left carb (more than the right carb due to bizzare airflow within the cowl). The miniscule particles within the exhaust gas are migrating thru the air fliter, into the carb, up into the air chamber and over time . . . shazam . . . I have a problem.
So, asking the experience guys; is this a practical explanation for my "black powder" in the carb air chamber?
Anybody else seen something similar?
Oh, BTW, haven't completed reassembly just yet, don't know if it fixed the start problem.
Thx much for your comments.
