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Marvel Schebler Carb issue on c90 J3

PoolGuy

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Hey Gents -

I've been chasing a WOT engine roughness and few hundred RPM drop on climbout in my J3 with c-90 ... Carb heat makes it go away as well as pulling the power back ... I tried plugs, drained and cleaned the gascolator as well as checked screen in carb. I also pulled the drain plug on the carb and got what looked like some metal shavings out of it. After some reading I checked the Throttle shaft and there is some visible play in it on the port side near the accelerator pump. See 5 second video here -
... Thoughts? Looks like that could cause a lean condition at WOT?

So I'm thinking it's time to send it off or replace with overhauled unit. I'm just outside Toronto, Canada ... who is the go-to shop? Plane is experimental btw.

Thanks!
 
Some play is acceptable but too much a d it will idle to high. Making it richer should help throttle response

Glenn
 
My issue is at WOT at climb-out ... it gets rough and loses RPM at 3-400 feet. Lowering the nose, and adding carb heat causes a significant drop in RPM and then it cleans up and is usually OK in cruise. I originally thought carb ice but it happens in all weather conditions starting last fall into the hot/humid days like now.
 
Have you drained the carb bowl? It will hold some water that will get ingested at higher AOA

Glenn

Yes. No water that I could see however I did get what seemed like metal shavings ... that drew my attention to the bushings.

I was unable to capture all the fuel/debris when I pulled the drain plug as I grossly miscalculated how large of a container I needed to catch all the contents! So there may have been water in there that was missed ... but not enough to catch my attention when trying to catch all the fuel.
 
The first few Legend Cubs had this issue with brand new O-200 and new carbs. It was a long time ago, but I remember it had something to do with the interface between halves of the carb. Same exact symptoms you described. It could also be too rich at WOT. Is this something that just appeared or been going on for a while?

Rich
 
Started last Fall ... Thought it to be carb ice ... stored for the Winter ... and then back at it this Summer. Definitely not carb ice. It's going lean as the plugs indicate as well as improvement happens when carb heat applied. I'm going to send the carb in for service. I'm just curious as to if that play in the throttle shaft as seen in the video is out of spec.
 
......I'm going to send the carb in for service. I'm just curious as to if that play in the throttle shaft as seen in the video is out of spec.

If curious about the degree of throttle shaft air leak carefully apply some "fuel" to that area while running and look for a marked increase in rpm. Fuel for example being propane from a long tubing or brake cleaner spray directed there. Overhaul is best of course so then you'll know it's airworthy.

Gary
 
I thought about that as I have lots of time on automotive carbs but it only seems to act up at full power ... I'm not interested in being near that area under power!
 
I thought about that as I have lots of time on automotive carbs but it only seems to act up at full power ... I'm not interested in being near that area under power!
Contact Jeff at msa carburetor and see if he will do a service on your carb and return it. Most of the time they want to do an exchange. Also the one piece venturi caused a lot of smAll continental woes, I went back to the 2 piece because my o200 ran like crap at 70% or higher. Good luck
 
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