I have a YS 120 that is producing air bubbles from the pump to the engine. Where do I begin to look for a leak. All of the nipples and lines are in good condition. When the engine runs you can see the bubbles coming from the nipple itself. All information would be appreciated. Thanks

Put a darker colored fuel line on it so you can not see the bubbles. That is what Y-S did on the newer engines.

The bubbles are caused by the heat of the engine.

thanks w8ye I later found that out looking at their website. Ialso learned that is normal from other long time modelers.