Frequently asked questions


Q-    My muffler is already tapped for smoke can I use the existing port?

A-    Many mufflers come pre tapped with smoke ports from the factory. Typical  smoke nipples inject a stream of oil straight through the fitting. BDS atomizing nozzles spray at roughly a 45° angle to the centerline of the nozzle. For best smoke performance, a new tapped hole positioned to direct the spray of smoke fluid across the exhaust port window opening.  Just not up and into the engine cylinder or onto the piston face.  This will produce the best results for your smoke system.   

Q-    Do I really need a check valve?

A-     A check valve will prevent siphoning of smoke fluid through your pump which can lead to smoke run-on when the smoke pump is switched OFF.  A delay or lag time can then be experienced when switching the smoke ON again as your re-priming the line.  Positioning a check valve just before the smoke nozzle will eliminate the lag time and provide more positive smoke switching at precise timing during your routine.

Q-     I’m setting up a twin cylinder setup and plumbing diagram shows multiple check valves. Why?

A-     A single check valve before a tee fitting split or no check valve at all will allow venting through the straight portion of the tee fitting leading to each nozzle. Uneven exhaust back pressure between cylinders can cause pressure or a venting action to force smoke fluid to the weaker cylinder. This can result in smoke run-on from one muffler or a loss of smoke line prime meaning slow smoke ON switching.  Some smoke pumps advertise no check valve required-  This is true for keeping the pump head primed, but this does not account for the inherent venting action of multiple nozzles when fed from a single supply line and tee fitting from the pump output.  

** Equal lengths of smoke tubing after the tee fitting & through the check valves,  continuing to  the smoke nozzles is also very important in maintaining equal back pressure.

Q-     Do nozzles require cleaning?  

A-      If running a rich fuel  premix ratio nozzles can occasionally carbon up.  This can be more common on 4 stroke engines.  Most nozzles can run for years without issues. A good practice is to remove and inspect smoke nozzles at the end of a flying season just as you would inspect or exchange fuel lines. If nozzles should require cleaning a simple soak in a carb dip such as barrymans carb dip and a scrub with a fine wire stainless steel or brass brush works well. A pipe cleaner and acetone can be used to clean the nozzle interior followed by a careful backflush of compressed air.  More aggressive cleaning risks damaging the nozzle and spray pattern. Please never pick or poke anything into the tip of your nozzle.  The tip can be damaged and spray pattern compromised.