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TOPIC: Cessna 150 Engine Issue

Cessna 150 Engine Issue 1 month 3 weeks ago #1644

Hi Carl,
Thanks for the information. We can check those too. Glad to hear your airplane is running well again!
Doug & Sandy
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Cessna 150 Engine Issue 1 month 3 weeks ago #1640

Suggestion, before you spend big money on the carb, check this. I had the same type problem on my c90 How many hrs on engine and clylinders.
Just completed annual on my plane, engine looked great, compressions, oil etc,, , had about 1800 at the time if not mistaken. . Son heads out to fly after the annual, has the same indications you mentioned, ( summertime too) Was able to replicated with a hot engine. Cyl #3 had very worn valve guides, this allowed the valves to "flutter" for lack of better term, as well as valve springs to get very hot due excess clearance. The engine would choke on the full power application for take off. If I had done the annual in the winter, may never have seen it manifest. I am cluing in the fact that leaning did not TOTALLY restore the power. Wanted to pass this on , easy to check before you spend some big bucks. I swapped out all the valve springs too, Cyl removal NOT necessary . Over 1/4 in difference in new and old. Ran like a top ever since. ( new guides in #3 )
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Cessna 150 Engine Issue 1 month 3 weeks ago #1639

Hi Steve,
Thanks for the reply. In answer to your questions... We've not relocated to a higher elevation. We've been at the same Iowa airport for just over a year (and came from another one in Iowa prior to that). We've only used 100LL for the nearly four years we've owned the airplane. We've not tried going past the 1700rpm run-up with the brakes locked, but it was smooth to there. We can try running it up higher. Both mags were serviced at annual this last May. The Challenger air filter was also cleaned and re-oiled at that time. We've not taken off and flown with the issue - we're just not comfortable doing that. I agree, our next step will be looking at the carburetor. We'll let you know what we find.
Doug & Sandy
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Cessna 150 Engine Issue 1 month 3 weeks ago #1626

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Hi Doug and Sandy;
It sounds like you have trouble-shot it pretty well. The carburetor is flowing too much fuel with the mixture control knob fully forward and the throttle fully open.
Some preliminary questions first. 1) have you recently relocated your 150 to a higher elevation airport? 2) are you using ethanol free auto gas? 3) Does the engine turn up to what's known as static rpm (full throttle or in this case smoothest rpm, brakes locked at sea level) between 2375 and 2475 rpm? This check is a rough way of determining if the engine is healthy; and 4) have the magnetos been retimed prior to the beginning of this problem?.
Have you taken off and flown with the engine leaned to smoothness?? How the the engine and airplane seem to perform? Did it seem to take the same amount of runway as before? Did it climb at the same rate as before??
There is very little that would cause an engine fuel air mixture to "go rich" Check your air filter for cleanliness, and check the inside of the carburetor air box for any obstructions.
If all the obvious things look normal, I suggest you remove the carburetor and send it to www.MSAcarbs.com. Request a flow check/test. MSA carbs has a sophisticated flow bench which allows it to determine if a carb is flowing the correct amount of fuel throughout the rpm range.
Let me know what you find.
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Cessna 150 Engine Issue 1 month 3 weeks ago #1620

I have a 1966 Cessna 150F that is running rough when trying to take off. The run-up is good and it is only at full throttle down the runway when the engine sputters and won’t make power. If I pull the mixture out during the take-off run, the engine cleans up and runs better. Pushing the mixture back in makes it sputter again which makes me think the engine is getting too much fuel. I have tried attaching a hose and blowing into the vent and I can see fuel vapor come out of both tanks with the caps removed. With the caps on, when I blow in I can hear a hissing sound from the hose. This makes me think it is not an over-pressurization problem. I also don’t smell or see raw fuel leaking from the carburetor but could the problem still be with the carburetor? Any insight is appreciated.
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