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MG TD TF 1500 - Is it mixture or timing?

I am embarrassed to ask this question because I should know the answer after all I have owned a Brit Car every year since 1956 and worked with SU's all during that time. I guess old age is beginning to settle in (67).
My BIG question: When the engine is cold , but starts right up, idles fine with enough choke to have it fire right up, but if I try to give it a little throttle (open the butterflys) it spits back out the carb, not quite a flame but spits out just the same with a nice scary pop. Once it reaches operating temp. (160deg) it never happens. I can give it all the throttle I want and and no problem no spitting. So, I ask is this related to mixture or Ignition timing (the only thing I haven't touched on the car)? Greg & Grimm
G.J. Cenzer

I vote for too lean! I would try the choke all the way out and ease off gradually until it starts to warm up. I would also check to make sure that the dampers are working okay...enough oil and that neither of the rods are bent as this could keep the dampers from sealing properly in their bores.
Steve Tobias

Steve,
Everything is new (rebuilt) throttle plates, shafts,needles,gaskets,seals,springs,jets,washers,fuel lines,banjos,cotter keys,etc.. Pistons work fine with no hesitation. Lift and fall smoothly. Slight problem with choke cable. Installed a new one from MUSSMTRS and the nut was too big and interfered with the secondary wood dash so I tried to grind dowd the sharp corners on the locking nut but it is made from cast POTMETAL and dissintegrated in my clamp as I was grinding, but I have over come that buy using circlips.
Greg & Grimm
G.J. Cenzer

Fllowed the shop manual exactly as far as setting jet adjusting nut and throttle adjusting screws. I have an air gage from my Rover 3500 days so I can set the velocity equal on both carbs. Test of lifting piston 1/32" on each carb at a time react as being proper adjusted. If I give it a real lot of choke it really puffs black smoke out the back. I'm still getting a blast out the carbs until she's fully warmed up. I need some thoughts from others. Greg & Grimm
G.J. Cenzer

If the mixture is lean there should be run on when a hot engine is is switched off and the idle rpm is 800 or more.
John James

I have occasional cold spits on our 1952 MG and quite often on the 1931 Model A. Problem is the valves sticking when cold. Once the cars warm up and the oil gets flowing, thngs settle down and run OK. I let them idle for a minute before taking off and avoid fast starts for the first mile or so. By then things get warmed up. I don't like to get up in the morning either, but the MG is 52 years old and the Model A is 73. It takes me a while to get going too.
John Masters

Well don't know what it was but it's gone now. fuel pump was always clicking nicely when ign was turned on. I did some deep thinking and said well I redid carbs, electrics, BUT I NEVER TOUCHED the pump. So I got out the manual and my SU tuning book on pumps and commenced to clean and check all parts of pump. Re-assembeled and now no spitting thru carbs, no loss of power when heated up just ran great today never missing a beat.
My prayers go out to all fellows in the hurricane area, hope all turns out OK.
Greg & Grimm
G.J. Cenzer

This thread was discussed between 27/08/2004 and 04/09/2004

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