I switched my SR22 to Tempest Finewires (€ 800 investment) and I like those much better. Runs smoother, starts even better.
Is there any chance you left the primer unlocked initially? This will allow extra fuel to be drawn into the cylinders from the gascolator and through the primer itself. It makes the engine run rough as you describe. If anyone doesn’t believe me then try it next time you’re in an aircraft. It will chuff out an excessive amount of black smoke at the same time. The primer doesn’t need to be pulled out far for this to occur, just unlocking it and pulling it 1/8" will do it.
Running rough with both mags on, is not usually a mag/problem.
After that, it may be flooded that prevented a further start. Best to walk away, have a coffee or two and sneak back to it after the excess fuel has evaporated.
Most Lycomings start on one mag as only one has an impulse coupling. The ignition switch has a link to earth the non-impulse mag out when selected to ‘start’. O-235s in C152s normally have dual (Slick) impulse mags, PA38s don’t and can be even more of a pain to start than a 152. Impulse coupling springs go weak and are normally the cause of intermittent starting issues on most Slick mags.
In my humble experience of maintaining a fleet of PA28-161s and many privately owned and operated PA28s etc for many years, I have never found (in the UK) the need to lean on the ground. My 200hp RV-6 preferred as do other 200hp+ Lycomings and TCM engines to be leaned out on the ground for taxying.
Strangely, the Warriors (161) often foul a top plug with a sliver of lead that leaning at power wouldn’t clear.
181 Archers exhibit a definite stumble in the rpm as the throttle is advance through around 1500rpm as the carb goes to the main jet – very noticeable if you open the throttle slowly.
PS Follow Lycoming’s shut down instructions and it will help keep plugs cleaner:
There are scavenging agents in 100LL that are designed to prevent plugs from fouling but work at higer combustion chamber temperatures than encountered at idle.
Prior to shut down, run the engine up to around 1700-1800rpm (as long as you’re not blasting anyone or anything behind, especially open hangars…) for 15-20 seconds. Then back to 1200 and instantly to ICO.
This works well – especially with O-235s that are mobile lead generators – even with REM37BY plugs installed.
I don’t want to be the smart guy here. But:
I fly diesel. You just turn on the ignition and start. Fouled plugs, leaning during taxi, magnetos, LOP, ROP, EGT? This all doesn’t exist in the diesel world…
The problem is that the engines don’t exist either, at least not yet, and for most of our planes.
If you run a nuclear reactor, you don’t worry about the gas pipeline. But you might have still have some problems, here and there 
Maybe even a little complicated preemptive maintenance, now and again. 
Hi aerofub,
Thanks – to you and all other posters for their opinions so far.
Is there any chance you left the primer unlocked initially?
Hardly. The primer in the Archer III is a push button rather than the pull lever in the Cessnas I know. It cannot and does not require to be locked. Also, AFAIK, it has no effect as long as the fuel pump is off?
After that, it may be flooded that prevented a further start. Best to walk away, have a coffee or two and sneak back to it after the excess fuel has evaporated.
That was our guess and I have walked away twice now for a 24 h coffee and snack break. This has not helped and finally, we’re giving up and the club’s mechanic is going to come up to Hamburg and check what’s going on…
181 Archers exhibit a definite stumble in the rpm as the throttle is advance through around 1500rpm as the carb goes to the main jet – very noticeable if you open the throttle slowly.
What we experienced on Sunday was definitely not just a definite stumble. ;-) Really, the entire aircraft was shaking around violently…
There are scavenging agents in 100LL that are designed to prevent plugs from fouling but work at higer combustion chamber temperatures than encountered at idle.
Prior to shut down, run the engine up to around 1700-1800rpm (as long as you’re not blasting anyone or anything behind, especially open hangars…) for 15-20 seconds. Then back to 1200 and instantly to ICO.
This Piper has been modified to run on MOGAS – not sure about the applicability of this then?
Is there any chance you left the primer unlocked initially? This will allow extra fuel to be drawn into the cylinders from the gascolator and through the primer itself. It makes the engine run rough as you describe.
That happened to me once. The rough running was pretty amazing.
In my humble experience of maintaining a fleet of PA28-161s and many privately owned and operated PA28s etc for many years, I have never found (in the UK) the need to lean on the ground.
That’s my experience, too. In my previous flying life (80’s-90’s) ground leaning was not an issue. It never happened and was never even discussed. In 12 years of flying back then (including PA28-161s) I never had to abort a flight because of a rough running engine. A few times I did have to lean during run-up to burn off deposits, but that was all.
Ah, you never said it was an Archer III, just a -181 and I erred on the side of the more common.
My comment on plug fouling prevention was a general comment about good house keeping regarding plugs. Obviously when running on unleaded MOGAS, you unlikely to see any lead fouling. You may get a plug oiled up (very new or older engine) and the leaning out to clear/higher rpm at shut down theories should still work when using unleaded to combat oil contamination.
That’s my experience, too. In my previous flying life (80’s-90’s) ground leaning was not an issue. It never happened and was never even discussed.
And mine. At our flying school, we have a fleet of Pipers (different variants of the Pa28 and Pa44). We are not supposed to lean on the ground for fear that the students may take off with a too lean mixture in case they forget to push the lever back in during line-up. Especially when doing IFR training flights that require a large gap between the airliners we have to wait at the holding point for quite some time. On several occasions it took me 45 minutes (!) from start-up to takeoff. All the time with the engine at 800-1000RPM and full rich mixture. But maybe they adjust the carburetors specially for this kind of flying school operation?
