This is interesting as Russ and I got 2/3rds of the way through making a copy of the best silencer Heinkel offered. That being the oval one which was fitted to early three or four wheelers. This is a very complicated bit of kit inside. It has three chambers and about 5 cross pipes. It is also stronger as the pipes are in the middle rather than the far end where they get increased leverage in shaking. Most Trojan type era silencers loose their tailpipes.
While this project was in work I offered them to the Club. They were not very interested despite my having a prototype cutaway that shows the internals along with two halved originals used as patterns. The claim was that the club silencer was just as sophisticated inside. I have no reason to doubt this, save cost. I know what ours will cost and Russ makes original and modified Messerschmitt silencers which are being greedily bought direct from him since the MOC took a decision to create a situation leading to dispensing with his services thus removing there 40 plus % mark up on the product. Seems a bit of an own goal but what ever, good news for the Schmitter, as Russ bits are now cheaper and available to all not just members of that single club! He also makes Tiger exhausts and lots of panels and brackets while I am banging that drum. See
www.messerschmittclub.org.uk known as KaRoScene.
The Heinkel exhaust is actually a tuned instrument and applies certain two stroke principles to get the gas moving. Just bunging a random box on it does not work. This was proved back in the day with MIck Leeson as Bismark had a home made extractor system as part of its modified engine. This unit would burn off a Messerschmitt and do 60 mph. Admittedly not for long but that was as far as we got before Mick died. A tragedy for many reasons apart from the expectation of a big valve, oil pump served cross drilled crank with small oil cooler, downdraft powered engine that would have resolved the heinkel engine issues and offered more reliable power.
The centre pipe Russ exhaust will be completed and made but only once Russ has caught up with his Messerschmitt parts orders and got his house finished. I am confidant that once put on a few cars it will be seen to be a superior item just as his other units are.
Sounds like you have checked the usual suspects. Bing carbs are passed masters at supplying weak mixture as they leak air like a sieve. The Pallas is a much better item, but rarer, as it has a slide seal and tuffnel sleeve sealing the manifold joint. The slide is less prone to wear as well.
The advance and retard is greatly ignored on Trienkels. It is not sufficient to check the unit is rotating. They have a issue where the hard steel of the bob weight springs wear away the bob weight making the assembly loose and ineffective. Once certain then the timing can be played with. Fuel has been changed in the period you have not been running the car. It has more volatile gases in it. I do not know the characteristics to advise but I suspect it burns faster as there is less energy in the fuel and thus the charge now. I certainly had to wind the Steyr Puch engines way back to stop predetonation. Ignoring three sets of timing marks on those engines must mean things have changed in terms of fueling.
Lastly make sure the heater flap is closed so the maximum amount of air is passing through the cowling. There should be a prescribed gap, not least filled with the usual missing warm/cold start nozzle, between exhaust silencer and the exit for hot air. If the silencer is shoved up hard against the exit of air it will interfere with air flow out of and round the engine, possibly passing it over the carb plus radiate heat back and even boil up the petrol in the tank! Hot fuel is not only rather dangerous but it weakens the charge making the engine run off true.
Lastly if you have a in line fuel filter fitted, get rid of it. Air cooled engines do not like them. There should be a filter gauze around the float bowl union bolt.
