72 SU chokes stick

[THE73Z]

73, L24, with 72 SU's. Did a few searches but didn't find the answer, books aren't helping either.

Trying to avoid the inevitable learning by removal, disassembly, reassembly, and reinstalling... I know I should but I really don't have the time these days.

With the choke cables detached from the carbs, both chokes stick - the front considerably worse than the rear.

Can I remove and repair the chokes without removing the entire carb?

Do they just unscrew? I have an entire book on SU's that doesn't help at all.

Thanks, Z

[DaveN]

This site is a good source of SU info. It's run by British car buffs, but they admit the best maintenance articles available were written for Hitachi SU's.

http://www.teglerizer.com/sucarbs/index.html

Nozzles come out easily. Just take out the one screw at the bottom that attaches the linkage and disconnect the gas feed tube. If they weren't sticking they would fall out in your hand.

Sticking can come from a varnish accumulation if the carbs haven't been cleaned in a while, from the "anti-stick" coating on replacement nozzles, or from badly bent needles.

If they need cleaning you only need to remove the nozzles and dome/piston/needle assemblies to have access to all the areas that collect dirt. The carb bodies can stay on the car.

Here's the history of the nozzle coatings: The earliest Z nozzles had no coating and were sensitive to varnish/dirt accumulations. In late 71 or early 72 Datsun began using a thin black PTFE coating, but found it would begin wearing through in a year or less of service. They switched all replacement nozzles to a more durable but slightly thicker (clear, green tinted) coating in the mid 70's. That coating is soft and sometimes a bit too thick, making the nozzle OD a bit too big for the bores in the carb bodies and giving a sticky fit. When that happens you have to polish the nozzles by hand (with rubbibg compound, hard finish cloth, etc.) to reduce the coating thickness.

Bent needles are the least common cause of a sticking problem. The wear they cause isn't repairable, both needles and nozzles have to be replaced. (With 72 carbs you can ignore instructions about aligning nozzles in the carb bodies. That only applies to 70-71 bodies.)

[THE73Z]

You're awesome!

Thank you VERY much.

Z

[Bruce Palmer]

... Our JUST SUs video ZTV09 might be a good thing to have on the shelf. It will walk you thru all that and a whole bunch more.....

[THE73Z]

OK, so I took Dave's advice and polished the nozzles and now they slide up and down smoothly. However, there are some springs hooked onto the hose clamps at the nozzles that are presumably to keep the nozzles in the up position when the choke is off. But they only seem to cause the nozzles to bind (because they pull at an angle) and seem like somebody's quick fix.

With the choke cables properly adjusted, the springs seem completely unnecessary if not detrimental to the performance of the choke.

Are the springs OEM or Jackass installed?

Thanks, Z

Btw, after wrecking my back for an hour bent over the engine bay, I discovered that the carbs are at the perfect height to work on by kneeling next to the front tire. OMG, what could be better!