Tillotson help please


I have a hr196 alcohol carb on a sudam 125cc the problem is it will not fire or refire after 10 min or so with out cupping/choking carb .The carb has had new seat gasket ect and pop off is set at 13lbs holding 11 .Is this pop off to high causing a no fuel signal upon start ? The carb running sounds good and crisp but the starting of it ? Any help would be greatly appreciated

alvin l nunley

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I had a problem, don't know if it's similar to yours, but maybe. After coming off the track, the heat of the engine and carburetor would build an air bubble that would force the fuel back towards the tank. Once I noticed this (I was running direct drive) I would choke the carburetor with my hand and rocked the kart back and forth (it was direct drive) and this would let the pumpers clear the air out of the line, letting the fuel back into the carburetor. Don't know if this is your problem, but it's worth a shot.
I agree with JT you need to be around 8 for alky, especially with the HR196 because it has the biggest venturi of all the HR's at 1.300. Fulcrum height is critical, .065 below the body with no gasket is the alky setting. when you richen both of those parameters be prepared to bring the needles in some.


This along with what jon brogden stated , seems out of whack .
He's talking about the body where the main gasket sits, I mean the little channel it sits in. I don't know the numbers, I just know they get pushed down sometimes. I'd check the gasket holes for the pumper too.


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Sorry for changing the topic of this post but I do have an HR191G EC built for an ope n2 cycle engine a friend of mine had and I have been using it on my Sudam. Very pleased with it but at the last GN it was not holding pop off pressure anymore and this particular carb was built with a special ball jet valve or Grose jet which is not sealing anymore. That caused the engine flooding which took me to close needles more than I should and stuck the engine. I am calling EC Carburators but I guess it is gonna be very difficult to find that kind of seat and ball anymore unless my friend finds a spare one in his shop. Any help? This has been by far the best carb I have ever had in any engine.
Might help both carbs with a new ball valve. Speed Parts Company had them a couple of years ago. I bought some from them. Google speedparts.com. It is a vintage engine shop.
Rainman , that carb should have slots machined in the seat threads like the newer Tilly's come stock with, if not it's an easy machine job. With the slots in place , fuel can exit two .050 cross holes in the bottom of the seat and enter the body plus all the fuel that can slip by the needle itself. Bottom line is it will deliver plenty of alky even for the bigger engines and seal up good. No need for a grose jet in a Tilly with the newer seats and the vertical slots.

Can you describe what you mean by "slots machined in the seat threads". Does this mean a slot from the low speed to the high speed inlet passages in the carb body itself or something else ?

Bob K.
Bob , I'm referring to the threads that the inlet seat screws into, two vertical slots opposite each other, 1/8 inch long shank mill to reach it, radius is plenty big cut in about .050. Stay about .050 off the bottom if your cutting one and leave an old gasket in while you find the bottom, mill not turning would be a good idea. For the fuel delivery to the high and low side pickoff holes they used to be called, I do a Y-slot which is a better version of the old T-slot with better flow and a shorter path.


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Thanks, Jon. I do not own the right machine equipment and I am not travelling in a near future to visit my friend Troy in VA, who is the one who has all the machines we use to work on these engines/carbs, so I might send it to EC Carburators.