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How Do I Adjust The Spring Tension In The Demand Regulator?

Published: 11/25/2016


This Information Will Be Helpful In The Event You Wish To Change The Spring Tension
Most Engines will run fine with the spring tension in the demand regulator set to the factory specifications. However there are times when an engine does not build as much vacuum as an identical engine setting right next to it, there is no rime or reason as to why this happens occasionally, 99.9% of all engines work fine at the factory settings. The symptoms are usually that the engine will not stay running after it starts unless you push the manual primer in, this can be caused if the engine is not building enough vacuum to pull the diaphragm down against the valve that allows the gas to flow which can be fixed by adjusting the spring tension in the demand regulator. The other thing that also causes the same symptoms is a vacuum leak somewhere, so it's best to check for any possible vacuum leaks first to rule out this issue.

To Adjust The Spring Tension
There is a screw driver slotted brass plug above the inlet on the front cover of the demand regulator, this is a locking plug against the adjustment plug under it which is where we will make the spring tension adjustment. Once you have removed the locking plug, you will find there is also lock tight on the adjustment screw or plug, you will need to turn this adjustment screw inward about 2 turns so you can get to the threads that have lock tight Using a pic or sharp point as found on the end of a 12 volt test probe, you will need to clean the lock tight out of those threads. Than apply WD-40 and proceed with turning the adjustment screw outward.

How Far To Adjust the Adjustment Screw
You can leave the locking plug out of the unit until you find the point at which the engine continues to run without pushing the manual primer. Here's a good example, let us just say that before you removed the locking plug, you counted 6 threads showing which is deeper into the chamber, so you might try backing the adjustment screw outward about 5 or 6 turns, which would then leave about 1 thread showing after you re-install the locking plug. If this is too far out or not enough spring tension you will know as the engine will flood out and quit running. You can also check to make sure you have enough spring tension by turning the gas supply on and simply listen for any flow of gas going through the demand regulator, if there is you will need to turn the adjustment screw inward until there is enough tension on the spring to stop the flow of gas, we only want the gas to flow when we push the primer, or once the engine has started and built up vacuum to pull the diaphragm down against the spring and opening the valve. Another way to check is to remove the vapor host between the demand regulator and the adapter, from the adapter end of the hose, leaving the hose connected to the demand regulator, then apply a soap bubble over the hose opening, if the soap bubble breaks then there is gas flowing through the demand regulator and you need to turn the adjustment screw inward until the soap bubbles do not break, which means there is enough spring tension to keep the gas from flowing until the engine has started and the engine vacuum pulls the valve open.

If you have any questions on this procedure please call us, we are here to help.


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