I had a similar problem with my c-90 with a marvel schebler carb suddenly it got worse found the accelerator pump had rust and debris under it and throttle would only open about 1/2 way because of the way the linkage works. Lucky I was able to get off the water and make it home.
0320 150 loosing power?
- Thread starter scottsville
- Start date
mvivion
SPONSOR
Bozeman,MT
There is an AD on the stock Cub muffler that requires a wire bail be welded up inside the exhaust pipe to prevent broken baffle pieces from blocking the exhaust.
if you have other muffler, not required. A bore scope will tell you if there’s junk floating around inside muffler in any case.
MTV
scottsville
Registered User
Well I flushed the carb. No change. We ran compression check and the engine was cold. 78-77-78-74 So I don't think it is the engine. Ordered new exhaust system for it and hopefully have a guy coming to check mag timing.
skywagon8a
MEMBER
SE Mass MA6
Make certain that he checks the internal timing in the mag, not just the timing of the mag to the engine. Just adjusting the timing of the mag to the engine does not correct the deficiency. If he understands mags, he will know what I speak of. There appears to be many who claim to know, but in reality do not.
wireweinie
FOUNDER
Palmer, AK
Just gotta ask. What issue did you find that made you order a new exhaust system?
Web
mike mcs repair
Registered User
chugiak AK
that was my thought also.... don't just throw parts at it...
wireweinie
FOUNDER
Palmer, AK
Exactly.
Web
Web
BC12D-4-85
SPONSOR
Fairbanks, AK.
Hopefully Scott has a source of good maintenance to help figure this loss of power out....like valve timing and lift plus fuel and ignition. Compression is only one component. It takes the rest to produce power. Plus a tach check.
Gary
Gary
Wouldn't a slow power loss over time have to be cam wearing? I would think that if the mags were causing that much of a problem the individual mag checks would be very poor.
I have seen the question asked but not answered, did the engine sit inactive for any length of time?
I have seen the question asked but not answered, did the engine sit inactive for any length of time?
gntw
SPONSOR
Ft. St. John BC Can.
just did an annual on cub with similar problem but had leaky ex on 4 pulled cylinder found ex lobe worn and lifter spalled. Pulled engine 1+2 in lobe worn 2 ex worn .only cylinder making full power was 3. Engine ran good. Just had prop strike inspection done 2 years ago and 140 hrs. No corrosion in side. Did another cub engine 3 yrs ago because of corrosion and low leak down cam had pitting but still good.replace with diamond coat lifers.did another cub engine last winter for prop struck.was 12 years old had 1800 hrs used 3 months out of year sitting 9 months in open air hanger . Inside the engine looks like new . Just inspected redid with mandatory parts . Cam was as new.
Akbushrat
Registered User
I was on floats and I could not get the rpm above 2000 rpm. So out came the aluminum anchor (on floats) and gave the muffler the anchor enema and low and behold, 2500 rpm. Then flew the river home and changed the muffler. Sometimes looking up the exhaust stack its not apparent whats what. 82-41 propellor.
Sent from my iPad using SuperCub.Org
Sent from my iPad using SuperCub.Org
BC12D-4-85
SPONSOR
Fairbanks, AK.
A typical measured orifice leak down check of compression reflects cylinder seal to leakage....rings and valves plus any fissures. It does not directly address how well the cylinder fills with air, just how well it retains whatever enters. A running compression check is often better for that. Rotate the engine with the starter and determine how quickly and to what ultimate pressure it builds with a gauge screwed into a spark plug hole.
That's where valve timing and lift can be inferred relative to power...that value is affected by worn cams and lifter bodies or compressed valve lifters. Then there's typical exhaust pressure reversion that when peaked can fill a cylinder over 100% volume capacity, and intake tract restrictions that inhibit flow often to certain cylinders like some exhaust systems also do.
Saying the compression is ok is only one component of several that should be looked at if power is declining.
Gary
That's where valve timing and lift can be inferred relative to power...that value is affected by worn cams and lifter bodies or compressed valve lifters. Then there's typical exhaust pressure reversion that when peaked can fill a cylinder over 100% volume capacity, and intake tract restrictions that inhibit flow often to certain cylinders like some exhaust systems also do.
Saying the compression is ok is only one component of several that should be looked at if power is declining.
Gary
