Cessna 150 not holding idle...Recent engine overhaul

D

DiveFlyDrive

Filing Flight Plan
Joined
Sep 22, 2018
Messages
4
Display Name
Display name:
DiveFlyDrive
Hi all, I would like to say thanks for all the support I have found reading through this forum! That being said, I haven't found very much on this specific issue so I figured I would make a post.

Cessna 150 with recently (150 hours) overhauled O-200 Continental. Runs fine above 800rpm. Won't hold idle below 800rpm. Mixture has been played with and adjusted, timing has been adjusted, idle is set at 550. Seems to behave better when warmed up but still sputters, vibrates, and shuts down. Don't want to lose it on short final. What do YOU think?
 
Last edited:
It’s got to be a carb issue if I had to guess, if not that check the mags and plugs. 550revs seems like a low idle, so you may want to adjust that a little higher. 600-700 range seems to work well for both of our 0-235’s.

Disclaimer, I am no mechanic so take my advice for as much as you paid for it.

We do have several experienced A&P’s on the board that can offer some advice.

@Tom-D @Dan Thomas
 
Last edited:
Ryanb said:
Disclaimer, I am no mechanic so take my advice for as much as you paid for it
Click to expand...
Hey! Can't knowing I'm having a good day be payment enough?! :p That is what I am thinking too, just isn't getting enough fuel to operate at low rpms... worried it could be a sign of something worse though.
 
Take a picture of your carb data tag and post it here.
 
Poor idle is a classic symptom of an intake air leak.
 
Idle is too low, are you sure your tach is accurate. And you will not loose it on final, the prop will windmill faster than 800 rpm.
 
flyingbrit said:
Poor idle is a classic symptom of an intake air leak.
Click to expand...
That there. It's an induction system leak. That system has five gaskets, eight hose connectors, eight hose shims and sixteen hose clamps. It also has four injector port plugs and two primer ports. Plenty of places for a leak, and that leak doesn't have to be very big either.

And I'll bet that the rebuilder might also not have used the Lock-O-Seal washers above and below the carb spider, and the retaining nuts are possibly done up real tight. It's an obscure part of the overhaul manual that gets ignored, and some O-200s have acceleration issues because of it. It doesn't cause an induction leak; it allows the engine to shake the daylights out of the carb and slosh fuel out the vent into the carb throat.
 
Awesome, thanks for the replies.

Tom, I will send that to you the next time I am at the airport.
 
Dan Thomas said:
That there. It's an induction system leak.
Click to expand...
Not necessarily. Some of the new carbs from Kelly do this right out of the box.
There are about 5 things that will give these symptoms.
I would venture guess that during the overhaul the carb was installed wrong by not using a "Stato-Seal" as mounting hardware.
I want to see the data tag to insure they put the correct carb on it, the 0-235 carb's part number will give these symptoms too.
Jumping to conclusions with out knowing the whole story seems to happen a lot here.
 
DiveFlyDrive said:
Awesome, thanks for the replies.

Tom, I will send that to you the next time I am at the airport.
Click to expand...
was the carb replaced during the overhaul?
There are 4 part numbers that will fit and give you these symptoms. If it was replaced, do you have the 8030-3 tag to see which Part number you bought?
Was this carb reworked during the overhaul? (as in some one had it apart)
 
Tom-D said:
Not necessarily. Some of the new carbs from Kelly do this right out of the box.
There are about 5 things that will give these symptoms.

I want to see the data tag to insure they put the correct carb on it, the 0-235 carb's part number will give these symptoms too.
Click to expand...

Possibly a bad carb. Kelly screws up a lot of stuff. But I'd still be looking for induction leaks first. Taking carbs off and installing new carbs is a waste of time unless the more common faults are ruled out.

It's an O-200, not an O-235.
 
Dan Thomas said:
It's an O-200, not an O-235.
Click to expand...
Every one knew that.
the 0-235 carb will fit the 0-200, but it doesn't run well and gives the same symptoms. many times when ordering they confuse the 152 and the 150 and receive the 0-235 carb and install it.

the new part number for the 0-200 carb is 10-4895-1 That will be a Kelly re-build, with a yellow data tag.
One word of caution,, if you run auto fuel you void the warrantee on the Kelly carb.
If you wish to run auto in a 0-300/0-200 find a unmodified 10-4895, or have me build you one, they run about $1800 if you have no core.
 
Tom-D said:
Every one knew that.
the 0-235 carb will fit the 0-200, but it doesn't run well and gives the same symptoms. many times when ordering they confuse the 152 and the 150 and receive the 0-235 carb and install it.

the new part number for the 0-200 carb is 10-4895-1 That will be a Kelly re-build, with a yellow data tag.
One word of caution,, if you run auto fuel you void the warrantee on the Kelly carb.
If you wish to run auto in a 0-300/0-200 find a unmodified 10-4895, or have me build you one, they run about $1800 if you have no core.
Click to expand...
Tom-
Can you do that? I thought there was some sort of process one needed to go through to change a plane such as a C-150 or C-152 to run on auto gas. I thought that because the EAA, or Peterson, has done some testing and can supply an STC (for example, see: http://www.autofuelstc.com/stc_specs.phtml ). For a Cessna 150, the EAA apparently has an STC: https://www.eaa.org/eaa/pilots/EAA-STC-Program/auto-fuel-stc

Edit: I didn't know that you could make the changes on your own.
 
Last edited:
Cap'n Jack said:
Edit: I didn't know that you could make the changes on your own.
Click to expand...

No one is making changes. the 10-4895 is the OEM carb, any A&P can repair and return to service.

both the 152 and the 150 have STCs to run auto. Want to run auto? don't run a new Kelly rebuilt, JMHO
 
The carb was serviced during the overhaul, I will find the part numbers this weekend. It has the STC and has had auto fuel run through it. Likely going to have it in the local shop early next week.
 
Tom-D said:
No one is making changes. the 10-4895 is the OEM carb, any A&P can repair and return to service.

both the 152 and the 150 have STCs to run auto. Want to run auto? don't run a new Kelly rebuilt, JMHO
Click to expand...
I knew the 150 and 152's have the Autogas STCs, as per the links I cited. I thought one had to purchase those STCs to run autogas in accordance to the regulations. I didn't think an A&P could just sign off on running auto gas on those planes.

Oddly enough, I don't think an A&P is needed to put the stickers on the plane once the STC is purchased.
 
DiveFlyDrive said:
The carb was serviced during the overhaul, I will find the part numbers this weekend. It has the STC and has had auto fuel run through it. Likely going to have it in the local shop early next week.
Click to expand...
Serviced??? not knowing what was done, hard to tell what is wrong now.
If you are running auto fuel your carb should be configured as they were prior to 1990, with a brass float, 2 piece Venturi, old style atomizer nozzle.
The Kelly rebuilds have a yellow data tag, plastic floats, rubber tipped inlet valve needle. They will run about 1 gallon richer per hour, causing (in some cases) fouled plugs.
 
Cap'n Jack said:
I knew the 150 and 152's have the Autogas STCs, as per the links I cited. I thought one had to purchase those STCs to run autogas in accordance to the regulations. I didn't think an A&P could just sign off on running auto gas on those planes.

Oddly enough, I don't think an A&P is needed to put the stickers on the plane once the STC is purchased.
Click to expand...
STCs must be applied IAW the STC instructions, and be recorded on a 337 by any A&P, then returned to service by a A&P-IA.

Blocks 6&7 of the 337.

""I didn't think an A&P could just sign off on running auto gas on those planes.""

did I imply they could?
 
Last edited:
Tom-D said:
""I didn't think an A&P could just sign off on running auto gas on those planes.""

did I imply they could?
Click to expand...

Since you ask, no mention of the STC was made in your reply:

Tom-D said:
Every one knew that.
the 0-235 carb will fit the 0-200, but it doesn't run well and gives the same symptoms. many times when ordering they confuse the 152 and the 150 and receive the 0-235 carb and install it.

the new part number for the 0-200 carb is 10-4895-1 That will be a Kelly re-build, with a yellow data tag.
One word of caution,, if you run auto fuel you void the warrantee on the Kelly carb.
If you wish to run auto in a 0-300/0-200 find a unmodified 10-4895, or have me build you one, they run about $1800 if you have no core.
Click to expand...

Thank you for answering my questions and happy Thanksgiving!
 
Last edited:
Tom-D said:
Serviced??? not knowing what was done, hard to tell what is wrong now.
If you are running auto fuel your carb should be configured as they were prior to 1990, with a brass float, 2 piece Venturi, old style atomizer nozzle.
Click to expand...

98-01-06 PRECISION AIRMOTIVE CORPORATION: (...)

(3) If a one-piece venturi is already installed, or installed in accordance with sub-paragraph (2) of this paragraph, and the engine subsequently runs rough or experiences power loss, accomplish either of the following:

(i) Modify the carburetor in accordance with paragraphs (c), (d) or (e) of this AD, as applicable; or

(ii) Install a carburetor containing a two-piece venturi and resume the repetitive inspections required by paragraph (a)(2) of this AD.

(b) For Precision Airmotive Corporation Model MA-3 series carburetors: at the next annual, 100-hour, or progressive inspection, whichever occurs first, after the effective date of this AD, inspect the carburetor to determine if the primary venturi is loose or missing. If either of these conditions are found, prior to further flight, repair the carburetor by installing a serviceable two-piece venturi, or replace the entire carburetor with a serviceable carburetor. Repeat this inspection at each annual, 100-hour, or progressive inspection.

(c) For Precision Airmotive Corporation Model MA-3SPA series carburetors with part numbers (P/N) 10-4894 or 10-4115-1, installed on Teledyne Continental Model O-200A series engines modified on or after the effective date of this AD by installing a one-piece venturi, install a new fuel nozzle in accordance with Precision Airmotive SB MSA-7, dated September 30, 1994, at the time of installation of the one-piece venturi.
 
The old-style venturies are rare. Most got trashed. One rebuilder I know used to dress the three legs of the one-piece venuri with a small file to smooth off that square profile and make them more like the old style's legs. More streamlined. It was his theory that the flat bottom surfaces and sharp corners on those legs caused turbulence that upset the flow and made mixture distribution very uneven and inconsistent. He had some good results with that.

I had hoped that Kelly would have sorted out the performace and quality hassles of those carbs. Guess not. When they started overhauling alternators they were putting far too much grease in the rear bearing, and it would get out and contaminate the rotor slip rings and fail the alternator's output. Hartzell has been doing that too. Both of them, for years, can't seem to understand that. Aircraft quality. Pffft.

Avstar also makes those carbs, but they're a milled body instead of cast. I have only had experience with one of them, an HA-6 on an R182. It ran OK, but then the original HA-6's ran OK too. It's the MA series that are so poor.

http://www.avstardirect.com/
 
JAWS said:
98-01-06 PRECISION AIRMOTIVE CORPORATION: (...)

(3) If a one-piece venturi is already installed, or installed in accordance with sub-paragraph (2) of this paragraph, and the engine subsequently runs rough or experiences power loss, accomplish either of the following:

(i) Modify the carburetor in accordance with paragraphs (c), (d) or (e) of this AD, as applicable; or

(ii) Install a carburetor containing a two-piece venturi and resume the repetitive inspections required by paragraph (a)(2) of this AD.

(b) For Precision Airmotive Corporation Model MA-3 series carburetors: at the next annual, 100-hour, or progressive inspection, whichever occurs first, after the effective date of this AD, inspect the carburetor to determine if the primary venturi is loose or missing. If either of these conditions are found, prior to further flight, repair the carburetor by installing a serviceable two-piece venturi, or replace the entire carburetor with a serviceable carburetor. Repeat this inspection at each annual, 100-hour, or progressive inspection.

(c) For Precision Airmotive Corporation Model MA-3SPA series carburetors with part numbers (P/N) 10-4894 or 10-4115-1, installed on Teledyne Continental Model O-200A series engines modified on or after the effective date of this AD by installing a one-piece venturi, install a new fuel nozzle in accordance with Precision Airmotive SB MSA-7, dated September 30, 1994, at the time of installation of the one-piece venturi.
Click to expand...
You do realize that a loose Venturi is very rare, they've had 7 in 35 years prior to 199? With that info Precision Airmotive got Terry Stoddard (of the SEA FSDO) to give them an emergency AD that started this whole mess.

This was the premier example of a company selling parts thru the AD system.
 
Tom-D said:
You do realize that a loose Venturi is very rare, they've had 7 in 35 years prior to 199? With that info Precision Airmotive got Terry Stoddard (of the SEA FSDO) to give them an emergency AD that started this whole mess.

This was the premier example of a company selling parts thru the AD system.
Click to expand...

Maybe, maybe not. Makes no difference at this point. An AD has been issued and needs to be complied with. If it comes to pass that the OP chooses to revert his carb back to a two piece venturi, then the AD inspections will come into play again. He should know that so he can make a good decision.
 
JAWS said:
Maybe, maybe not. Makes no difference at this point. An AD has been issued and needs to be complied with. If it comes to pass that the OP chooses to revert his carb back to a two piece venturi, then the AD inspections will come into play again. He should know that so he can make a good decision.
Click to expand...
And lots of A&Ps require their owners to update their carbs because they are too lazy to do the AD, I've even been told by A&Ps that the carb must be removed to do the Venturi check.
 
You must log in or register to reply here.
Back
Top