You wrote "Moving chock in and out after first start makes no difference."

Hi Harvey.

Yes it looked like a VERY tiny valve seat insert but it was brass - no need for a separate machining in a brass jet. It was also inside the screen, on the wrong end of the orifice. It could have been swarf, but it looked too perfect. It was so small I had to stick it to electrical tape to keep a hold of it. I remain puzzled!

The carb, ordered new, also came with both dashpot springs. Found that when trying to find the problem. I only used one of them, but don't recall which one!

Moving the choke in/out should decrease/increase the rpms. The choke mechanism on the carb has a cam. When the choke is pulled the cam contacts a screw on the throttle cam which turns the throttle which ads rpms. It is possible the choke cam is not hitting this screw. You need to adjust the screw out so that the choke cam  

Dan, you mentioned a piece of unauthorized brass. I was thinking you meant trash/shrapnel/swarf. Your second picture sure looks like a tiny valve seat. Just curious, does the carb inlet needle close into a pressed-in seat? Maybe that one got lost. Harvey

With a HIF6, it most likely has a spring-loaded metering needle, so it should not be sticking in the jet.

Suspicion turns to the fuel inlet needle and jet.

You need to remove the carb and invert it to remove the bottom bowl cover. (You may need a fresh rubber seal to get it back on later.)

1. Check for dirt.
2. Check the float is moving freely. If not, determine why. Remove the float.
3. Inspect the bi-metal lever that adjusts the metering jet to see that it is in its proper position. Don't move the idle mixture screw.
4. Remove the bi-metal lever to access the inlet jet.
5. Remove the float, being careful to not shift its adjustment tab.
6. Remove the inlet needle and inspect it carefully. Is it clean? Is the tip perfectly formed or is is showing wear or distortion?
7. Using a socket wrench, remove the brass jet.
8. The jet should have a tiny filter screen on it. Inspect it for dirt.
9. Remove the filter screen from the jet. Look for debris inside the screen and in the jet orifice. (See note below)
10. Check both the fuel inlet passage and the overflow passage are clean and clear.
11. Once you are satisfied everything is clean and proper, reassemble in reverse order.

I had similar problems with a Brand-new HIF44 (6) that stymied even a pro Mini mechanic. When I got down to removing the filter screen, I discovered a tiny piece of brass as shown in the second photo. (An undocumented factory-original special part??) It would bob around in there and occasionally settle over the orifice, blocking the fuel supply. You may have something like that going on.

Another thing I had great trouble with was the inlet needle sticking, but it would occur when the engine was hot. It was an interference issue where he needle and/or jet would expand with heat and eventually stick, usually in the open position. The engine would flood. Not your problem, but it shows how finicky these thing can be.

My suspicions are you have a piece of debris causing an obstruction or your fuel inlet needle is sticking in the jet. These come in various types - beyond my pay grade. Since your carb was recently rebuilt, find out what type is in there and try changing the needle and/or jet.

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Cholk is working fine. It does as you noted and is used to turn the car on. The problem is the needle or float, just not sure what to look for when I take the carb apart.

Moving the choke in/out should decrease/increase the rpms. The choke mechanism on the carb has a cam. When the choke is pulled the cam contacts a screw on the throttle cam which turns the throttle which ads rpms. It is possible the choke cam is not hitting this screw. You need to adjust the screw out so that the choke cam contacts it when you pull out the choke.  

Electric fuel pump and I hear it working fine. Carb was recently rebuilt with all new seals. It’s a hif6 with the float bowl below the carb.

Are you using the choke to start it? Yes using the chock to start. Does using the choke make a difference? Moving chock in and out after first start makes no difference. Does it start OK on the second try? Once the carb is tapped, and whatever is stick frees up, it starts and runs perfect, no issues.

You did not say if it was a HS type or HIF type.
What type of fuel pump do you have - electrical or mechanical?

For either, Ian's suggestions apply.

Are you using the choke to start it?
Does using the choke make a difference?
Does it start OK on the second try?

 Running for only 15 seconds suggests to me that the weather and engine may be too cold. 15 seconds is not long enough  to warm anything up. On a HS type, the "choke" moves the jet down to provide a richer mixture to overcome cold starts. On a HIF type, the "choke" opens a valve in an auxiliary passage to provide the richer mixture.

A 15 second run and tapping on the side of the carb to make it work suggests to me that the fuel inlet float valve is sticking. While the car sits, perhaps some of the fuel in the bowl evaporates, leaving only enough for the short run. When you tap on the carb, it knocks the needle loose and the bowl gets more fuel. The answer to that is to remove and clean the inlet jet and needle, and then check the float level - easy to do on a HS type where the bowl cover can be removed. For a HIF type, it requires removal and dismantling of the carb.

Fuel Pump: When I start my Mini, I turn the ignition on ("run" position) and listen for my electrical pump to fill up the carb - usually 2-3 clicks. Then I turn the key farther to crank the engine. With a mechanical pump, you have to crank the engine until the carb fills.

I think I would be looking at the needle and seat first...

Have you tried sticking your finger down the carb and seeing what sore of response you get when you lift and let the piston drop???

Cheers, Ian

When the car is turned on from cold start, it runs for 10-15 seconds before turning off. It will not start again until you hit the side of the carb. This does not happen when warm. What to look for?