Ive noticed something interesting with my pponk engine...im not really concerned with it but it is very different then what i would expect out of a carbed engine.

Ive noticed it more lately with ambient temps being higher now...getting near 90.

Once ive run the engine, and shut down for fuel or any reason, if the engine is still warm or hot, i have to almost hot start it like a fuel injected engine, which is fine since i fly the biggest pain in the ass injected engine of them all in a turbo baron!

I can crank with the mixture rich, and it will just crank away, if i go idle cut-off and open the throttle while cranking the engine will start right up with no problem whatsoever! Ive never been in a non fuel injected plane that ive ever seen that done to start a hot engine.

Its a ported and polished engine, and ive been told that when you polish them out it doesnt "mix" the air and fuel in the cylinders as well, im thinking this could possibly be the situation here...any ideas??


Mike

Procedure I use on my Pponk when motor is hot and will have a hot restart is to kill engine with mags not mixture. Then on restart no prime, throttle barely cracked, crank and when fires feed a little more fuel. I had hot start problems when killing with mixture and either priming or too much throttle on restart.

My experience with a couple different Pponks has been that if I so much as breath on a knob, be it throttle or mixture, it is going to require a hot start procedure like you describe. But if I just get back in, turn the key and hit the switch it lights on the first blade...

My experience has also been that the carbs could stand to be modded richer...

It got me for a while too. The old O470 like a hint of prime to start when it was hot. The PPONK just fires up by turning the key. If your engine is actually flooding when you shut down, You might want to take a peek at the carb. Perhaps the float isn't seating the needle all the way and fuel is dripping down the throat.
RP

Are you running MO gas? If so its boiling in the carb, not uncommon this time of year with the winter blend, as for polishing the ports causing a problem like this, not a chance. DRP1 suggestion is on the money.

Does your 520 Pponk conversion shake or vibrate or tick.

Two years ago a good friend and I send 2 470 engines down to a well-known Pro in the lower mainland for the 520 conversion.
Received and installed into our 180’s we both installed the new three bladed Hartzel propellers.
My friends motor was near perfect with good oil pressure from top end to hot idle, but seemed to vibrate in flight mostly at cruise power setting and some days it seemed worse than others.
His idle was rough like a camed up race car engine. We did hear that they do idle lumpy. My motor ran terrible, a shake in flight to periodically stumbling in flight. The idle was rough and hard to keep running on start-up. Seemed like you would have to keep priming, select carb heat or rev-up to 1500 RPM when cold. My oil pressure high as 50 PSI flying but down to 5 PSI at hot idle, a big variance. We consulted the PRO’s numerous times on the oil pressure as well as vibrating issues and lots of recommendations like some guys are installing sea plain engine mounts to change your balance tube, your fuel supply line lost its flex. Your vacuum pump hoses are hard, cowl flap hinges are loose. To even as stupid as your tires are too big. We even talked to Hartzel numerous times.

My engine also developed oil leaks one mag quit working lifters periodically started ticking and still impossible to set idle mixture setting, with roughly only 20 hours on the engine. The supplier agreed to look at it. This time I flew it down to him. Our time and expenses plus four hours X 2 plane, rooms’ meals, gas and the return home.
Several weeks later it’s ready. 6 lifters changed new rod bearings, high flow oil, pump installed, new carburetor and no more leaks. This is all under warranty all I have to pay for is the new oil and filter?
Because I was on holidays my two good buddy’s went down to retrieve it. His remarks were it still vibrates and shit idle, but no oil leaks. Seen 80 PSI oil pressure but still in red at hot idle?
Now spring time and I am back in town a few test flights around town and off to anchorage airmen show on an 8hr flight of periodic stumbling with some vibration. I am still not happy. I get my prop balance in anchorage and that did help some. On the return flight home 2 more lifters started ticking periodically and then quit! No problem the pro sends me two more under warranty I just have to pay someone to put them in? Still hard to keep running on cold start up and definitely worse at sea level. The PRO’s comments were you should always select carb heat hot on start up?
I guess I have to change my start up procedures on the engine. Always tipping me off that it’s, just me, now with numerous flights of stumbling and vibrating.

And 85hrs on the engine. I was in Spring Bank Alberta a 3hr light home after start up I noticed lifters were again noisy. Things seemed ok on run up, so I taxied for runway. There was heavy traffic and I get pressured into take- off which was not good. On the climb the shake was terrible the compass was unreadable. You would have sworn I lost a propeller blade. I do engine checks, fuel checks, I select carb heat hot. This was not good descending into Terrain. So carb-heat cold after gaining some altitude it cleaned up again so I continued home. We diagnosed this problem with a mechanic and we were finding the lifters were bleeding down 3-5 min after started up. That is unheard of.
I now have had enough and out with this engine and sent it to someone new.
Good for my first supplier but bad for me. He just cut off any warranty issues and if I have any more issues or complaints I would have to contact his attorney. I guess I should have returned to Spring Bank and condemned it right there, then I might have had a case then.
Torn completely down and reassembled the main bearings were changed, rod bearings, 12 new factory lifters (with high flow exhaust lifters meaning I should have lower oil pressure at idle). They used the same oil pump. On the top ends assembly they find the valve covers painted or powder coated internally and peeling off, possibly making its way to the lifters, Beed Blasted out cleaned and assembly completed.
On their test run my oil pressure variance tightened right up 80-40 not 80-5 and even with high flow lifters, but they don’t collapse anymore, so my valve lifters are cured! Next they can’t get my carburetor to idle so they think I need a new one a bigger one from my 4893 to a 5284. Aware of my rough idle and hard to keep running cold issue I agreed and all on my own expense! Another motor job, another carb and nothing on warranty, what’s next?
Well finally installed and onto start up, oil pressure is really good way better but this carb different again, real smooth slow idle but 1200 RPM not so much shaking, black smoke just pouring out. Good top end on test flight, I am impressed with the top end power and smoothness but shake in flight with power cut back? Pull carb heat on and shit just about killing engine. Different yet again so out with this carb now onto the third one. Send back to the new supplier upon arrival the yellow tag saying repaired.
I get curious and give the shop a call to discuss what was repaired and not much! Checked out float level it was ok. I put back in box and sent back well what the hell? He’s calling it primer leaks or balance tube problems. Yah right just like the rest!
My buddy and I are calling it carburetor problems so out with buddy’s carburetor a 4893 the same as what I started with, and shit just about perfect! A lumpy idle to kick ass top end so it is the carburetor causing lean at the bottom end shake, hard to keep running, shaking in flight to my periodic stumbling in flight all these issues were just the carburetor!


We get into the air metering JET or also called the mechanical air bleed enrichment circuit and its wire tied with a lead seal on it on the base flange of the carburetor.
First setting on my OID carb the 10-4893-1 was screwing the JET out one turn and this made it worse and impossible to keep running at cold idle, and shake in flight just like a prop blade was missing. Next adjustment was screwing this JET seat in 2 turns. Now the cold start-up was good no more staling, no more selecting carb heat hot to keep idling. Run up through RPM was almost perfect, so then we tried right to end of adjustment just before the butterfly won’t open fully. Boy what difference start up perfect, idle perfect right down to the 500 RPM. No more camed up race car, really amazing to watch the prop swing around with no shaking. The test flight turbine smooth with no periodic stumbling all the vibrating issues are gone!
It’s all in this air setting not liking this adjustment screwed all the way in. We decided to play with the 5284-1 brand new Carb, so we cut the wire and lead seal off and screw the seat out one turn for a leaner mix and wow its perfect! Low end idle to top end power- no more flooding at 1200RPM selecting carb heat on final was now normal drop in RPM.
My buddy quite mechanically inclined gets his wife to print out a precision air motive MSA float carburetor hand book and troubleshooting techniques. Everyone including the PRO’s should read this and in there under the trouble shooting top end or low end rough engine rich, (Economizer setting misadjusted).
Rough engine lean, (Economizer setting misadjusted) and many other troubles leaning to this adjustment.
Then reading farther on settings they say the carburetor setting for this roughly ½ inch in from base, (ROUGHLY)? Well mine was less than this and my buddies was like ¾ inch in, that’s a big difference in performance and the only reason his motor ran better than mine at this time.
So the question is (what carburetor to use)? The 10-4893-1 with the air bleed or economizer jet setting screwed all the way in to make it run richer or the 10-5284 and adjust to make it leaner, or are the modifications incorrect? we also adjusted my buddies 10-4893-1 carb in approx. 2 ¾ turns to end of adjustment for perfectly smooth idle to almost perfect top end.
Earlier on before we go into the carbs he also changed his lifters from remanufacture to factory made this was an improvement, but not like this carburetor settings. This setting has a plug that’s wire tied and a lead seal crimped into it. The PRO’s tell me you cut that seal you can’t return it and plus you’re not allowed to. This got us thinking even more of how often has this metering jet been apart or cleaned? On the back of the carburetor is an air vent cap under this cap is a fine screen like filter not completely plugged but right full of dirt, lint and rust. This is very important for this circuit to work right!


This shit was in there for a long time and definitely not from my few hours of flying. This circuit was not even looked into when the carburetor was modified who’s to say maybe the wrong jets are being used.
End result I don’t recommend rebuilt lifters your (valve covers shouldn’t be internally painted). Your fuel economizer air mixture bleed screw setting is very important and can cause your engine to vibrate in flight, rough idle, rich vibration, lean vibration, hard to keep running at idle when cold, periodic stumbling in flight. Vibrate on full power the PRO’s can’t tell you anything about this setting or don’t even know other than the lead seal is a don’t go there zone! Print out and read the hand book it could save you a lot of money.

Cliff Nelson
(250)262-2891