[TR] Dieseling and pinging

Randall tr3driver at ca.rr.com
Mon Oct 12 12:55:38 MDT 2009


Sorry for the delay, Wayne, I'm still cleaning out my inbox after TRfest.

> Any instructions for adjusting ZS 175 carbs ?

Try Nelson's article at
http://www.buckeyetriumphs.org/technical/Carbs/CarbsIII/CarbsIII.htm

> The Bentley manual instructs me to raise the piston inside 
> the carb air inlet 1/4", and if the engine idle has an 
> immediate increase, it means the carbs are set rich, if not 
> the carbs are weak.

Those instructions don't' necessarily apply to 'emissions' carbs.  They are
supposed to idle somewhat on the lean side.

> Should I touch the carbs to try and fix my pinging and 
> dieseling issue?

The pinging is unlikely to be carb adjustment, IMO, unless the engine is
also overheating.  I would look first to fuel and ignition timing to solve
pinging issues.

However, getting the idle rpm down will definitely help with dieseling.

On my Stag ZS carbs, I found that the idle adjustment was not lowering the
idle rpm with the vacuum retard disconnected.  It turned out that the
throttles were being held open by the float bowl vent valves, and the
provided adjustment for the vent valves did not have enough range.  I had to
bend the clips somewhat to get it all adjusted properly.

Of course, the other option is to reconnect the "anti-run-on" equipment,
which the factory added in 1973 precisely because these engines have a
tendency to run-on (aka diesel).  There is a solenoid mounted to the bottom
of the carbon canister, which applies manifold vacuum to the canister and in
turn the float bowls when the engine is shut off, in order to prevent
dieseling.

-- Randall  


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