View single post by Darth V8R
 Posted: 03-10-2023 02:37 am
PM Quote Reply Full Topic
Darth V8R



Joined: 12-27-2022
Location: Beaverton, Oregon USA
Posts: 37
Status: 
Offline
 What makes you say the needles are too lean? Are you using the "lift the slide" technique to read the mixture? It is extremely technique sensitive, and if done incorrectly (as it almost always is) it will show the carbs as lean.

When using the lift the slide technique, you lift the slide approx 0.5mm (0.020"). The engine speed will change according to the mixture but only for about 2 seconds, and then will return to a normal idle. If the normal idle does not return, you did the test incorrectly (probably lifted the slide too much) so try again. The idle speed will change a very small amount (less than 100 rpm) so you must listen carefully.

If this sounds tricky, it is because it is. I gave up trying to get repeatable results, and now use plug cuts exclusively. You can also use a color tune or O2 sensor.

As to a source of needles, the best source is Burlen Fuel in the UK. I counted about 80 different needles for the Zenith carbs using the 0.10" jet, and a similar number for the smaller Zeniths. Be aware however that Burlen's web site lists only a small sample of what they carry. Get their hard copy needle catalog and it lists everything. If you know which needle you want, you can do a search on their web site and the needle will come up even if it is not listed in their on line catalog.

Joe Curto is also an excellent source, although he does not carry every needle.

Vance

Last edited on 03-10-2023 02:43 am by Darth V8R