0-200A correct idle speed and best deal on new MA-3SPA carb...

[150GFlyer]

I've gotten some conflicting info on the idle speed for the 0200A and i'm wondering if any of you experienced 0200 gurus might have some input on this.

I've found from different sources on the web idle speed recommendations any where from 525-800RPM. Continental doesnt list an idle speed in its specs for this motor... so whats the best idle speed (sea level elevation) that wont load the plugs? 525 seems way too low to me and i know i've read plenty of people stating that you want the idle higher, more like 800 so any expertise out there would be greatly appreciated.

Also, where can i find the best price on a quality overhauled MA-3SPA Marvel Schebler carb? They are $700 + $600 core on Spruce's site.
I've found them at Air Power for $569 but its the AvStar version which i'm not familiar with... anyone have experience with the newer style AvStar carbs?

 

[Skylane81E]

Assuming a 150 from the screen name, Cessna gives the idle speed.

 

[Dan Thomas]

800 RPM is too high. Such power makes landings longer and burns out brakes during taxi.

You can minimize plug fouling by leaning for taxi and by running the engine up to 1700 or so for a few seconds just before shutdown.

What's the matter with the old carb?

Dan

 

[150GFlyer]

Our 150 is a recent purchase and it seems to run a bit rough at warm idle, around 575rpm.
Cold idle is about 700 and seems much smoother. Im suspecting possible timing adjustment needed and maybe points/dwell.
Starts easy and seems pretty smooth otherwise. My partner is my brother who is a longtime AP and professional avionics tech but most all of his experience is in the big jets from his Air Force and Airborne Express days.
We were thinking about replacing the carb with a fresh rebuild just to be safe since the plane has been run partially on Mogas and hasnt flown a lot in the past 6 years. Less than 10 hrs per year. Figured if it has sat with mogas in the carb it might be a good idea to replace it for our own peace of mind, may not need it but couldnt hurt.

Anyone have any experience with the Avstar carbs?

 

[Tom-D]

500-550

NEVER buy a new carb, repair the one you have.

disassemble clean, replace the parts that it requires, and reassemble.

the new carbs are crap that run WAY too rich and foul plugs.

the OEM carb will run 5-6.5 GPH, the new Kelly aerospace carbs will run 7-8 GPH and are not auto fuel approved.

 

[150GFlyer]

Thanks Tom D that is good info to know. I hadnt heard that before. We both have rebuilt carbs many times.. There isnt anything especially difficult about these Marvel Scheblers is there? I believe we will read up on the OH manual and check into a kit. Seems i've seen them running about $450 or so (yikes!).
Seems kinda steep for a carb overhaul kit. Im assuming it will come with the newer design floats (gold plated?.. Ha)

 

[Tom-D]

Thanks Tom D that is good info to know. I hadnt heard that before. We both have rebuilt carbs many times.. There isnt anything especially difficult about these Marvel Scheblers is there? I believe we will read up on the OH manual and check into a kit. Seems i've seen them running about $450 or so (yikes!).
Seems kinda steep for a carb overhaul kit. Im assuming it will come with the newer design floats (gold plated?.. Ha)

DO NOT buy a kit, buy only the parts required, and never sign it off as a rebuilt, or overhaul, because there is a mandatory parts replacement list. simply repair it and place it back into service

Yes the parts kits are priced stupidly.

I have a supplier in BC that has the total inventory of Precision Airmotive when they went out of the carb business, the accelerator pump is $110. and the top plate gasket is 47 bucks.

never go to the single piece Venturi. stay with the 2 piece, and do the 100 hour AD.

Replace the throttle shaft bushings as needed, they are 37 cents at ACE hardware. ream to fit your worn shaft, and this carb will run for ever.

Never use the newer floats, they are plastic and auto fuel eats them for breakfast.

 

[Dan Thomas]

never go to the single piece Venturi. stay with the 2 piece, and do the 100 hour AD.

Very good advice. There were three iterations of that AD, as I remember. The original demanded that the two-piece venturi be replaced with a new one-piece to preven the secondary venturi's loosening end getting sucked into the engine. This new venturi had squared-off support legs that cause turbulence and poor homogenization of the mixture, and consequent rough running. An amendment to the AD demanded a new crossdrilled fuel nozzle to better atomize and homegenize the flow. It didn't work well in most cases, so another amendment allowed you to reinstall all the old stuff and check the venturi for looseness every 100 hours. Good deal, except that Precision had taken back the old venturis and destroyed them, and most of us were stuck with the new junk. One rebuilder I know would smooth off those support legs and get smoother operation.

An associated problem with rough running on the O-200: The intake manifold (known as the spider) is mounted on two studs under the crankcase. The IPC shows Lock-O-Seal washers above and below the spider on both studs, and the overhaul manual instructs you to do up the castellated nuts finger-tight and install the cotter pin. I have learned the hard way that there is a reason for this; if the nuts are done up tight, the engine's vibration will shake the carb side-to-side and slosh fuel from the bowl vent into the induction and cause some really rough performance at certain RPMs. The whole thing needs to flex on those studs, damped by the intake tube rubber sleeves.

Dan

 

[Tom-D]

Very good advice. There were three iterations of that AD, as I remember. The original demanded that the two-piece venturi be replaced with a new one-piece to preven the secondary venturi's loosening end getting sucked into the engine.

[COLOR=[B]"Navy"]No, it simply gets loose twists side ways and stops being a venturi. and the engine quits due to no fuel flow.[/B]
[/COLOR]

This new venturi had squared-off support legs that cause turbulence and poor homogenization of the mixture, and consequent rough running. An amendment to the AD demanded a new crossdrilled fuel nozzle to better atomize and homegenize the flow. It didn't work well in most cases, so another amendment allowed you to reinstall all the old stuff and check the venturi for looseness every 100 hours. Good deal, except that Precision had taken back the old venturis and destroyed them, and most of us were stuck with the new junk. One rebuilder I know would smooth off those support legs and get smoother operation.

An associated problem with rough running on the O-200: The intake manifold (known as the spider) is mounted on two studs under the crankcase. The IPC shows Lock-O-Seal washers above and below the spider on both studs, and the overhaul manual instructs you to do up the castellated nuts finger-tight and install the cotter pin. I have learned the hard way that there is a reason for this; if the nuts are done up tight, the engine's vibration will shake the carb side-to-side and slosh fuel from the bowl vent into the induction and cause some really rough performance at certain RPMs.

They will not do that when the float level is set correctly.


The whole thing needs to flex on those studs, damped by the intake tube rubber sleeves.

Dan

The 3 ADs were a direct result of the Precision Airmotive lawyers trying to sell parts by AD.

 

[Dan Thomas]

They will not do that when the float level is set correctly.

We spent two weeks fooling with the carb on an O-200, having it overhauled by two different shops and having everything double-checked, including float level. It wasn't until I discovered that little paragraph about the finger-tight nuts and special washers (rubber inserts in them) that we finally got the thing to stop barking and hesitating and losing RPM in the takeoff roll.

Dan

 

[Tom-D]

We spent two weeks fooling with the carb on an O-200, having it overhauled by two different shops and having everything double-checked, including float level. It wasn't until I discovered that little paragraph about the finger-tight nuts and special washers (rubber inserts in them) that we finally got the thing to stop barking and hesitating and losing RPM in the takeoff roll.

Dan

That's a new one on me, got P/Ns for the washers?

 

[Dan Thomas]

That's a new one on me, got P/Ns for the washers?

538556. from the manual:

Install lock-o-seal washers between the crankcase and intake manifold and below the intake manifold. When required, install the carburetor air box support assembly on the forward stud. Install castle nuts and tighten finger tight. Advance as required to install cotter pin. Do not use wrench on castle nut.
(See Figure 38.)


Dan

 

[Tom-D]

538556. from the manual:

Install lock-o-seal washers between the crankcase and intake manifold and below the intake manifold. When required, install the carburetor air box support assembly on the forward stud. Install castle nuts and tighten finger tight. Advance as required to install cotter pin. Do not use wrench on castle nut.
(See Figure 38.)


Dan

I just ordered the washers (Stat-O-seals) 1.87 each.

I have always placed a hard washer on top and below tightened a MS210--nut on until it was snug and backed it off 1/2 turn.

Show me some one who knows it all, I'll show you some body that scares the hell out of me.

I'm starting to worry about you.

 

[Dan Thomas]

I just ordered the washers (Stat-O-seals) 1.87 each.

I have always placed a hard washer on top and below tightened a MS210--nut on until it was snug and backed it off 1/2 turn.

Show me some one who knows it all, I'll show you some body that scares the hell out of me.

I'm starting to worry about you.

That figure I posted was shrunk too much. Try this one.

Don't worry about me. I'm not fixing little airplanes anymore. I'm working on Lockheed Electras, converted to bombers for firefighting. Learning all kinds of stuff I never knew. All big turbines, totally different wing structures, massive propellers. Almost 16,000 horsepower between four engines. The only disadvantage? I'm not qualified to fly them.

 

[Tom-D]

I'm working on Lockheed Electras, converted to bombers for firefighting.

Aerounion?

once upon a time I worked the gear box, torque meter, and power section shops at Whidbey. for the T-56-14A engine rebuild facility. (400 division)

 

[Dan Thomas]

Aerounion?

once upon a time I worked the gear box, torque meter, and power section shops at Whidbey. for the T-56-14A engine rebuild facility. (400 division)

Air Spray. Canada. They bought the Aero Union STCs after Aero went broke.

Dan

 

[150GFlyer]

Thank you Tom and Dan both for some very good information. Much appreciated.
Tom im wondering if you could PM me with the contact info for your supplier of the carb parts?

 

[Tom-D]

Thank you Tom and Dan both for some very good information. Much appreciated.
Tom im wondering if you could PM me with the contact info for your supplier of the carb parts?

As soon as I can dig it out.

 

[bluerooster]

Agree with Tom, just "IRAN" it, and be sure to install the new blue epoxy float.
I would also get a new accelerator pump plunger (MSSB-13), and pump discharge valve (depending upon the internal condition of the carb).
And check the play of the mixture control shaft, if there is excess "wiggle room", you'll need to install a bushing.
There is a service bulletin (MSSB-11 revA) concerning an improper repair to tighten up the mixture shaft, where the hole has been staked, a bushing must be installed if that is the case.

And for some reason, (don't know why) There are two gasket sets for the MA3-SPA
each set has it's own part number, and they are priced about $6 apart. But they both contain the same identical parts, with the same individual part numbers. I know this because I bought both sets from the same supplier, not knowing what the difference was. There is no difference other than $6.
Then you can log it as compliance with MSSB-2 revB, about float replacement.
and no overhaul has taken place.
Total cost of parts would be ~$300 or less.

 

[Henning]

I've gotten some conflicting info on the idle speed for the 0200A and i'm wondering if any of you experienced 0200 gurus might have some input on this.

I've found from different sources on the web idle speed recommendations any where from 525-800RPM. Continental doesnt list an idle speed in its specs for this motor... so whats the best idle speed (sea level elevation) that wont load the plugs? 525 seems way too low to me and i know i've read plenty of people stating that you want the idle higher, more like 800 so any expertise out there would be greatly appreciated.

Also, where can i find the best price on a quality overhauled MA-3SPA Marvel Schebler carb? They are $700 + $600 core on Spruce's site.
I've found them at Air Power for $569 but its the AvStar version which i'm not familiar with... anyone have experience with the newer style AvStar carbs?

Idle speed is not the primary factor in loading up really. The J-2 I flew on floats had an O-200 set with a idle below 600 and it ran just fine there without loading up, but I lean hard whenever at idle.

 

[Tom-D]

Agree with Tom, just "IRAN" it, and be sure to install the new blue epoxy float..

That plastic float is part of the problem, they are not
auto fuel compliant.

the good old brass float was good for 80 years. and still is.

 

[Henning]

That plastic float is part of the problem, they are not
auto fuel compliant.

the good old brass float was good for 80 years. and still is.

I'm with you, I prefer brass floats to poly. Even in cars when the formulation of gas would change we'd get a bunch flooding cars with saturated poly floats come in.

 

[flyer]

500-550

the new carbs are crap that run WAY too rich and foul plugs..

Thats not the experience I had when I bought a rebuilt carb for my O320 E2D. Mine was running way too lean and I had to send it back to the factory twice before they got the mixture set rich enough.

 

[bluerooster]

That plastic float is part of the problem, they are not
auto fuel compliant.

the good old brass float was good for 80 years. and still is.

Which plastic float? there have been many.

 

[Tom-D]

Which plastic float? there have been many.

Name one, they are all crap.

 

[Tom-D]

Thats not the experience I had when I bought a rebuilt carb for my O320 E2D. Mine was running way too lean and I had to send it back to the factory twice before they got the mixture set rich enough.

Doesn't that tell you that they can't get anything right.

Remember that "Kelly Aero Space" has been the parts manufacturer since the early 90's.