I just got our engine back from Aero Engines for the Pponk conversion and installed it. We're seeing a very large vibration from idle to 1750 RPM during ground runs. It feels like it's around 5 Hz at idle and is large enough that looking at the instrument panel will make you sick and is unairworthy. We adjusted the idle mixture both rich and lean, and ran the mixture control at all speeds trying to smooth it out with no success. Since it smooths out at 1750, the issue seems to be an idle circuit issue. We are running our original C66 prop that ran smooth prior to the overhaul, does not have balance weights, and is clocked as it was before. Lycon performed the carb modification and bench flowed it. Aero Engines performed a test cell run with this carb down at sea level prior to shipping to us here in Colorado at 5050' elevation.

We checked for leaks on the intake system and found nothing. Mag drops are equal at about 80 RPM. It doesn't feel like a dead cylinder but we can't be certain as we have only a single point EGT and cylinder temp. We checked all the mounts. I did buy a new Knisely exhaust.

Anyone have a similar issue with their Pponk conversion? The engine shop has a loaner carb that we are on the wait list for. Sounds like this must be common if they have a loaner carb....

Thanks!

I hung an overhauled 88" C201 on my 180 last year. Flw great, except when I slowed down in the pattern for the first landing. Just about abeam the numbers (can't recall the rpm), it developed a horrible shake. Prop shop recommended removing the propeller & turning it 180 degrees. Doesn't make any sense to me but that did the trick. Although even after dynamic balancing it's still not as smooth as my old 82" C203.

I put a P-ponk on early this year; no similar issues. In the absence of an multi-probe or other EGT; write with colored chalk on the exhaust pipe of each cylinder. Run it up; if it's a duff cylinder, it will retain its color. All the others will turn white. You can also do the runup on left and right mags after fresh marks, and determine which mag if it's electrical. HTH, Ron

Had a buddy with a Pponk 182 that did similar thing when they hung a Mac 401. It ran smooth prior with, I think, a two blade. Anyway, they could never get it right and I sold him my old C66, problem solved.

Also, when we installed the 0-470-U/TS with a fresh overhauled C204 the thing vibrated pretty bad below 2400RPM in cruise, and not smooth at idle/lower RPM either, tried turning prop 180 and only minor reduction. Went and had it balanced and it was like 1.46 out, not even on the pie chart!!! Got it down to .05 and it was tremendously better, gained like 200+ fpm, crazy difference. Thus, before y'all tear into the engine, might try balancing the prop.

Did you run it briefly and put your hand on the cylinders, that'll tell if you've got a dead jug? Also I've experienced similar symptoms from a dead spark plug, but a mag check should reveal that? Hope it's something simple, probly is since it was run on test cell. Let us know what happens!

All that above, including a couple of things. Like the chalk trouble shooting, go ahead and borrow a temperature gun. Run it with the cowl off and see if you see a cold cylinder. Also trouble shoot for a vacuum leak.

I doubt it is a dead cylinder as it smooths out repeatably as soon as we hit 1750 RPM.

Flat cylinder

Ace007 wrote:I doubt it is a dead cylinder as it smooths out repeatably as soon as we hit 1750 RPM.

Probably, but easy enough to check and eliminate. the temp would at least tell you if you fuel/spark issues at low RPM. I doubt it's compression, as I've seen a "o" psi cylinder (rings) run like a top. I fought roughness for a while on my 520.

Is the cowling on or off? Cowling rubbing on the exhaust makes a HUGE vibration in the airframe.
Pretty common after fresh installs due to new isolators and exhaust placement.
There is no "common issue" with the carb anymore then there is a common issue with any airplane carb. It's just a regular carb with a bigger jet and a different economizer adjustment.
All good suggestions so far. Here is the chalk stick. Electrical tape works the same way as well.

Did you rebuild the mags? Check the plugs? Single cylinder CHT/EGT is as useful as tits on a boar hog. Get a 6 cylinder CHT/EGT so you can see what is happening.
DENNY

Is your propeller indexed properly???

MTV

Prop an only go on in one of two ways, 180 degrees across from each other.
But as I pointed out in my case, turning it can make a difference.

Tried prop in both clocking positions - no change.

All cylinders are hot.

There is popping sounds in the mid range.

New carb shows up today.

The factory carb that was sent to us by the rebuilder ran great so it narrows it down to the Pponk'd carb that was performed by Ly-con. I'll keep this thread updated with what we find out for others. Very odd that the carb ran well for the rebuilder during the test cell run.

Thanks for the replies.

Just one more thing to verify. You do have an intake manifold with the crossover balance tube? I have had several friends that didn't have the balance tube and had issues after a Ponk upgrade. Installed the crossover intake and problem solved. Even mixture and no more lean hot cylinders.

RockHopper wrote:Just one more thing to verify. You do have an intake manifold with the crossover balance tube? I have had several friends that didn't have the balance tube and had issues after a Ponk upgrade. Installed the crossover intake and problem solved. Even mixture and no more lean hot cylinders.

Huh? There's big continentals that don't have a crossover in the intake system? I've never seen one. Those forward intake tubes do come in different sizes tho...

Ace007
So far I have found 27 variations of the MA-4-5 "series"
So far unable to determine differences.

Link has good info - have to scroll around a bit.

http://www.insightavionics.com/pdf%20fi ... Manual.pdf


There is another link but it did not look as good.
Will edit this POST if I can find more.

EDIT-1: See page 4 right column beginning with: ADDITIONALLY ---

http://www.kellyaerospace.com/articles/ ... ry_AMT.pdf


EDIT-2 Official service bulletin list:

http://msacarbs.com/technical-data/serv ... etins.html



Nuff for tonight

Halestorm wrote:

RockHopper wrote:Just one more thing to verify. You do have an intake manifold with the crossover balance tube? I have had several friends that didn't have the balance tube and had issues after a Ponk upgrade. Installed the crossover intake and problem solved. Even mixture and no more lean hot cylinders.

Huh? There's big continentals that don't have a crossover in the intake system? I've never seen one. Those forward intake tubes do come in different sizes tho...

FYI-The balance tube addition was per Steve Knop. Both times it solved the mixture issues. Just reporting what was done to solve the problem per the stc developer and owner.

RockHopper wrote:

Halestorm wrote:

RockHopper wrote:Just one more thing to verify. You do have an intake manifold with the crossover balance tube? I have had several friends that didn't have the balance tube and had issues after a Ponk upgrade. Installed the crossover intake and problem solved. Even mixture and no more lean hot cylinders.

Huh? There's big continentals that don't have a crossover in the intake system? I've never seen one. Those forward intake tubes do come in different sizes tho...

FYI-The balance tube addition was per Steve Knop. Both times it solved the mixture issues. Just reporting what was done to solve the problem per the stc developer and owner.

Ok, I'm confused.



Do you see the balance tube below the nose of the pictured IO-520? All 470 and 520 engines have one of these tubes that balance the intake. You're saying your friends were operating pponk O-470-50 engines that did not have such a tube? That seems impossible to me, they would have needed to plug the end of the intake with something.

I believe what happened was Steve advised them to use a different size balance tube, I would be curious to know what tube that was.


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I believe that you are probably correct on the larger tube size. It has been a few years, about 20 give or take, so the details are fuzzy. I remember that there were lots of issues with a couple of cylinders running lean and hot. Several different carbs with different jet sizes were tried and no real change. I believe that one of the installs was a replacement retro in an early 180 being updated to later style of engine. Maybe replacing an "A or J ". In the past I heard of engine builders that were " licensed" to build engines with the stc who were not complying completely. Call Steve Knop to get the exact details. He is very approachable and knowlegable. He built my last engine for me and is meticulous and reputable.