Tickler tech details so no flooding

Off Brit Iron List a few days ago.----


I like ticklers and think they are a good
addition to a motorcycle carb for someone how can use them.<<

I used to think that ticklers simply flooded raw gas into the intake, much like pouring some gas into a V8 carb throat will get a balky engine to fire.

But, that's not the way they work. If you look closely, the drain hole on the outside of the tickler is below the level of the intake port, and would never get raw gas into the cylinder.

There are really two carburetors in a concentric carb - the big one with needles and slides and all that, and a very small one called the pilot circuit which operates independently during startup and small throttle openings. It has a mixing chamber under the floor of the carb throat on the engine side of the main slide. It is supplied with air from the pilot air screw, and with gas from the pilot gas jet (a fixed brass jet .017" orifice). The pilot gas circuit pulls gas up from the float bowl through a relatively large drilled passage (about .125" IIRC). Since the pilot mixture vent in the carb throat is also quite small, it is very difficult to create enough vacuum when kickstarting a cold engine to fill the pilot gas passage with enough fuel to fire the engine.

Hence the tickler. It depresses the float far enough that fuel can fill up the pilot fuel passage to the pilot fuel jet. The tickler has a drain hole at the level of the pilot jet which prevents flooding raw gas into the intake. Once the engine is running, there is enough vacuum to keep the pilot fuel passage full, and it takes a little while after stopping to drain back down.

Hope that helps...

Mike Randell

Thanks,
Tom

Check out YouTube videos --"Stripping and servicing a Amal 930 concentric carburetor #1of2 and #2 of 2" to see Hobot's comments in action. The first time I had a cigarette in over forty years.

Tom