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DRG-ler · 06-07-2022, 02:40 PM

Hi guys, my A is giving me some problems.

It's consuming too much and backfiring on coasting/decelerating.
What has been checked so far... A pressure drop test was done which showed no problems. Inlet valves, outlet valves, piston rings were tight.
The engine got a new head gasket. A visual inspection of the valve seats was also carried out there. Also without any abnormalities. Also, no stuck/hanging valves were found when turning by hand. (The problems existed before the head gasket was replaced.)

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ignition

Ignition was set according to the setting instructions and checked with a flash gun. Ignition timing with the lever at the top is 0 degrees.
Capacitor on ignition distributor was measured and declared to be functional.

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Carburetor

Carburettor got new jets. Jets are flow tested by David Renner.
With the new jets, the engine runs much cleaner and quieter, and starts better. But the misfires remain!!!
Only the running was tested when stationary, not while driving! Furthermore, the float level was readjusted. The Schmimmer is now at 15.5 mm with the needle valve fully closed. About 5/8" as I could see in a YT video. Measured to the carburetor body separation. Furthermore, it makes no difference whether I screw the idle mixture screw all the way in or out. The engine doesn't run any differently, and it doesn't stop either!! Even a change to the GAV does not bring any change! (Should actually only be under load / driving.) Loud popping / misfires when going down EVERY gas shock!

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manifold

The intake/exhaust manifold was reground together at the engine builder. This one is straight again. The seals are new and seated correctly. The manifold was sprayed with brake cleaner while the engine was running. He draws no secondary air, is not leaking! The carburetor flange was also sprayed off and is also tight.
The only thing that hasn't been replaced yet is the breaker contact. However, that's what my previous owner did. I think it hasn't done 5000km yet. The modern version has already been retrofitted.
Now the question is, where are the misfires coming from? These do not occur when driving under load when accelerating. Only when decelerating.

Greetings Andy

06-07-2022, 02:40 PM	#1
DRG-ler Senior Member Join Date: Dec 2018 Location: Berlin / Germany Posts: 182	Backfire, I'm running out of ideas... Hi guys, my A is giving me some problems. It's consuming too much and backfiring on coasting/decelerating. What has been checked so far... A pressure drop test was done which showed no problems. Inlet valves, outlet valves, piston rings were tight. The engine got a new head gasket. A visual inspection of the valve seats was also carried out there. Also without any abnormalities. Also, no stuck/hanging valves were found when turning by hand. (The problems existed before the head gasket was replaced.) ------------------------------------------------ ignition Ignition was set according to the setting instructions and checked with a flash gun. Ignition timing with the lever at the top is 0 degrees. Capacitor on ignition distributor was measured and declared to be functional. ------------------------------------------------ Carburetor Carburettor got new jets. Jets are flow tested by David Renner. With the new jets, the engine runs much cleaner and quieter, and starts better. But the misfires remain!!! Only the running was tested when stationary, not while driving! Furthermore, the float level was readjusted. The Schmimmer is now at 15.5 mm with the needle valve fully closed. About 5/8" as I could see in a YT video. Measured to the carburetor body separation. Furthermore, it makes no difference whether I screw the idle mixture screw all the way in or out. The engine doesn't run any differently, and it doesn't stop either!! Even a change to the GAV does not bring any change! (Should actually only be under load / driving.) Loud popping / misfires when going down EVERY gas shock! ---------------------------------------------- manifold The intake/exhaust manifold was reground together at the engine builder. This one is straight again. The seals are new and seated correctly. The manifold was sprayed with brake cleaner while the engine was running. He draws no secondary air, is not leaking! The carburetor flange was also sprayed off and is also tight. The only thing that hasn't been replaced yet is the breaker contact. However, that's what my previous owner did. I think it hasn't done 5000km yet. The modern version has already been retrofitted. Now the question is, where are the misfires coming from? These do not occur when driving under load when accelerating. Only when decelerating. Greetings Andy