D2 carb (@#$^%&*%#)

Cylinders flooded with gas?

well, I pulled the plugs and they seemed dry.

I poured some gas in to the neck of the carb, as a last resort, that found its way to the plugs.

well, I pulled the plugs and they seemed dry.

I poured some gas in to the neck of the carb, as a last resort, that found its way to the plugs.

That little plug in the bottom center of the bowl has a really small hole in it that usually gets plugged and wont let fuel through.

No EXTERNAL plug with a jet hole in it in the Zenith carb bowl. Lots of simple small air cooled engines do have that plug in the center of the bowl that holds the bowl on AND meters the gasoline into the carburetor.

However, there is a drain plug that if you can get it out with the carb installed will help you evaluate the supply of gasoline into the bowl. Turn on valve and then remove drain plug. If you get a gush and then just a drip you know your supply from the tank is restricted or float valve is clogged. Lots of the pony tanks are so full of rust and sediments that you can’t really get enough gas out of them to support the engine running under load. No amount of choke helps a supply problem.

If you remove the drain plug and get a gush and then a continuous flow of gas, you can eliminate the supply from the tank and float valve and move on.

Carburetors on ponies that will run only with a lot of choke can have the passageway across the bottom of the bowl from the main jet to the removable high speed metering well so clogged with crud that only reaming with a drill bit will restore them. I’ve had one I could blow compressed air through that was almost like a new engine after drilling the soft plug and proper cleaning. Only drilled it out in desperation but was pleasantly surprised at the response. Part of that cleaning process is removing the high speed metering well above the hex plug near the throttle body. I always clean it with spray, but I’ve never seen one clogged. The sediments seem to collect in the passage across the bottom of the bowl and not get up to the metering well orifice.

There is another passage in the bottom to the middle of the bowl where the compensator jet is located that can be reamed out only after drilling out a soft plug, but I’ve never done that one as long as I could spray carb cleaner etc through it. I might be missing something!

I’ve never removed the actual brass jets that are threaded into the bowl casting. Those are easily cleaned with plastic broom bristles, very fine wire etc. Tried to get one or two out once but it didn’t come loose so I didn’t persist in my efforts to remove them.

Another thing to check is that the gasket between the bowl and cast iron Venturi/throttle body is two concentric rings. Have heard of the center ring going missing and completely disabling the carb.

No EXTERNAL plug with a jet hole in it in the Zenith carb bowl. Lots of simple small air cooled engines do have that plug in the center of the bowl that holds the bowl on AND meters the gasoline into the carburetor.

However, there is a drain plug that if you can get it out with the carb installed will help you evaluate the supply of gasoline into the bowl. Turn on valve and then remove drain plug. If you get a gush and then just a drip you know your supply from the tank is restricted or float valve is clogged. Lots of the pony tanks are so full of rust and sediments that you can’t really get enough gas out of them to support the engine running under load. No amount of choke helps a supply problem.

If you remove the drain plug and get a gush and then a continuous flow of gas, you can eliminate the supply from the tank and float valve and move on.

Carburetors on ponies that will run only with a lot of choke can have the passageway across the bottom of the bowl from the main jet to the removable high speed metering well so clogged with crud that only reaming with a drill bit will restore them. I’ve had one I could blow compressed air through that was almost like a new engine after drilling the soft plug and proper cleaning. Only drilled it out in desperation but was pleasantly surprised at the response. Part of that cleaning process is removing the high speed metering well above the hex plug near the throttle body. I always clean it with spray, but I’ve never seen one clogged. The sediments seem to collect in the passage across the bottom of the bowl and not get up to the metering well orifice.

There is another passage in the bottom to the middle of the bowl where the compensator jet is located that can be reamed out only after drilling out a soft plug, but I’ve never done that one as long as I could spray carb cleaner etc through it. I might be missing something!

I’ve never removed the actual brass jets that are threaded into the bowl casting. Those are easily cleaned with plastic broom bristles, very fine wire etc. Tried to get one or two out once but it didn’t come loose so I didn’t persist in my efforts to remove them.

Another thing to check is that the gasket between the bowl and cast iron Venturi/throttle body is two concentric rings. Have heard of the center ring going missing and completely disabling the carb.

[quote="Richard~J~W"]Did I mention how much i hate petrol/gas motors?

I got a customer with a D2 that about 12 months ago started and ran fine, then last winter he rang to say "no starty, Boss"

Long story short after about 20 or 30 pulls on the rip cord we got the vaguest of murmurs that sounded like it might go, presumably a bit of vapour......but didn't

The magneto been cleaned and there's a handsome spark coming off it. It is timed correctly, on the "C" mark. The leads are the right way around and with the plug pulled we get a nice spark.

Took the carb off, cleaned it out, then today have been back to install....full of expectations and quiet confidence....well, it was a big fat nothing-burger. In fact it almost seemed it did the same, the murmur of a start, just to build up my enthusiasm, but nothing.

I took the lid off the float chamber, there is petrol/gas present. The little poppet is free and allowing fuel in.

I pulled the plugs out of the bowl, blew them through, all seems fine.


Can someone please give me a lightbulb moment and suggest anything else that it could be

thanks[/quote]
G'day Richard
Just pulled my pony down today out of my D4 7u and noticed the magneto was on the "M" mark. hope i'am right and this helps.
John