Zenith 40 TIN Jet Identification and Size

[dennisv]

Hi folks. I am rebuilding a set of Zenith 40 TIN carbs. I'm trying to confirm that the existing jets are correct. Looking at the factory manual, it appears that stock for a 1970-71 US with enrichment would be:

• Main Jet: 115
• Air correction jet: 195
• Idle fuel jet: 47.5

I believe the jet on the far left is the main. I can't find any markings on it. Is that normal?

The other two at least have marketings that appear to be correct. At what point do I just ditch them due to uncertainty?

[Nditiz1]

The one on the left is not the main unless you pulled it out of the holder. A side view would be a better determination. You should see 115 on the side. If unsure measure with a drill bit or jet measuring tool.

[dennisv]

Originally Posted by Nditiz1

The one on the left is not the main unless you pulled it out of the holder. A side view would be a better determination. You should see 115 on the side. If unsure measure with a drill bit or jet measuring tool.

Thanks for you assistance. I obviously don't know what I'm looking at! Here is the side view of the same part from the far left of the original photo. I still don't know what it is, but should be able to put it back where it came from if I look at my progress photos. Float bowl check valve?


I was not looking for a holder, but think I found it now. It says Solex 0115. So I guess I'm better off than I thought!

[targa72e]

I would check your jet sizes. The Zeniths I just rebuilt had idle jets that had been drilled out to 60. The hole is so small that they looked the same as stock. Since I had mixed parts from a couple different carbs I ended up with 4 idle jets at 60 and 2 stock 47.5. This made it quite hard to get the tuning to work

john

[Zuffenwerker]

Pin gauges are your friend on these old crabs…the rule of law is to file off the jet size if you drill it…most people break the law so you always got to check

[dennisv]

Originally Posted by targa72e

I would check your jet sizes.

Do the numbers found on Zenith, and presumbably Weber, carbs directly correlate to a size (i.e. the diameter of the orifice in hundredths of mm)? So main jet with stamp of 115 should measure 1.15 mm? I am reading that depending on the carburetor manufacturer, the numbers on jets could be arbitrary.

Originally Posted by Zuffenwerker

Pin gauges are your friend

Pin gauge sets are not cheap. It might cost me less to just buy new jets. Maybe I am searching for the wrong thing or in the wrong places.

[dennisv]

Now that I'm getting my bearings on jets, I'm trying to inspect them in more detail. It appears to me that one of them doesn't even have a hole. WTF? This is after it sat in carb cleaner overnight and then been brushed. Twice.