TR4/4A Strombergs again.....

[karls59tr]

After the motor has started and the choke pushed back should the carb pistons fall back down to the bridge...mine seem to be hanging up about 3/8" above the bridge?

 

[Sarastro]

They shouldn't fall all the way down when running, but they should when the engine is off. I don't know how high they should be, but 3/8" seems too much at idle. Do they move smoothly and drop all the way to the bottom when the engine is not running?

 

[Merlin63Tr4]

What is your idle speed?

M.

 

[karls59tr]

They shouldn't fall all the way down when running, but they should when the engine is off. I don't know how high they should be, but 3/8" seems too much at idle. Do they move smoothly and drop all the way to the bottom when the engine is not running?

When the engine is off they stay up. When the engine is off I can put a small screwdriver under the pistons and lift them up but they do not fall all the way down. The thing is this is a project car that is going up for sale so I do not want to get too invoved in overhauling the carbs but would rather leave that for the next owner. I was hoping there was a simple fix. I'm an SU guy and Strombergs have always intimidated me. Only thing I have done to the carbs is oiled the linkage and checked the diaphragms which appear new.

 

[karls59tr]

What is your idle speed?

M.

I haven't really got it to idle yet as I spent some time sorting out the ignition system and timing. I can get the motor to run with the choke fully out and carefully playing with the throttle otherwise it wont idle.

 

[pdplot]

Try this before going nuts. Loosen the screws holding the cap down and then try raising and dropping the piston. If it drops down, slowly tighten the screws a bit at a time and then test the piston drop.

 

[Merlin63Tr4]

Sounds like the jets/needles are not centered....

M.

 

[Sarastro]

The previous two suggestions are spot on, I think. The Strombergs are not that different in principle from the SUs--a binding piston will definitely give you trouble, but it can be easy to fix. Center the jets in the same way you would for SUs, and be sure the piston is not binding elsewhere.