air valve piston get stuck!

[richyboycaldo]

Hi, i bought two 240z one for parts and the other for restoring. a 73 (round carbs and a 71). he mecanic told me the carbs on the 73 air valve pistons were getting stuck because of use so the put the carbs of he 71 on the 73, and he later told me hat the air valve piston in 1 carbs is getting stuck because is to worn or used, but so every time i go to a yunk yurk its going to be he same and i don want to buy the complete carbs (i already have 4), could it be that he is NOT using the correct oil (eas 20 right??) o waht other factor can be? or simple i had bad luck with 3 worn pistons

[Ed]

Your mechanic is on the right track by replacing the 73 flat tops with the 71 round tops. The chances of getting 3 worn pistons seems a bit excessive. Maybe you should take your car to a different mechanic? When I was learning about the carbs the guys over at Z whizz helped me out, they are in San Diego just look them up in the phone book. Depending on conditions determines what type of oil will work best in your carbs but 20wt should do fine. I use ATF in mine and am very happy with it.

Instead of messing with these used carbs you should get some rebuilt ones from Z therapy this way you will know that your carbs are performing correctly. Get their tuning video at the least it will help you tremendously.

Whats a "yunk yurk"? Junk yard?

[richyboycaldo]

thx ED yeah is yunk yard sorry . i like ztherapy ,but there expensive (for me) i will probably search for another carbs on yunk yards, or another 240z that is full of rust taht are sold cheap, i bought one for 250 buks!!! while searching for carbs with rebuilt engine and trany but lot of rust inthe body. thx for the help ill go buy your oil

[Ed]

If your inclined to do a little work on your own carbs, take the bowls off and clean the piston with some fine steel wool. Use a little bit of carb cleaner to get all the deposits off. Lube it a little with the new oil and put them back together.

Becarful when you go to take off the screws that hold the bowls in place. Alot of times they are stuck and are a pain to remove. Tap them with a small hammer and put some penatrating oil on the screw from the bottom. If the screw doesn't budge first try then instead of taking a chance on stripping it use an impact screw driver (the kind you hit with a hammer).

Also remember how the bowl assembly goes. There is a spring in there that will come out when you remove the bowl. Take care not to damage the needle.

I think you will be wasting your money getting more used carbs. Remember all these carbs are 30 years old and most of them have seen atleast 100,000 miles. The brass shaft that holds the butterfly valve wears out and creates vacume leaks. Save your money and get the rebuilt carbs.

Good luck.