AFB Tuning

First you need to know if it is stumbling rich or lean. If you don’t know, you don’t know to add or subtract weight from the counter balance. You can try adding front jet, it will make the cruise rich, but it is only a test to see if it helps the opening. If it does, you are probably lean on opening. On some AFB’s there is a secondary enrichment port that the tip of the butterfly swings by. It pulls a bit of fuel to help with the secondary opening transition. I run an AVS and have the same issue, on the data it spikes lean at the hit. I have all the pump shot and drilled the shooter out a bit and I am definitely using the carb WAY out of its comfort zone. I can only tighten the air door spring so much. With an AFB you just might want to live with it. AVS and you can play around with it pretty easy.