Triumph Repair: 1964 Triumph TR4, john deer tractor, triumph tr4

Question
This year when I start the car, it backfires and bucks. It goes away when I pull out the choke but comes back. It takes about 30 minutes of driving around the city before it runs smooth. Any ideas? It was not happening last year.

Answer
Hi Paul,
Your symptom does not pin point the problem but you might first clean or replace the plugs and then check the oil in the top pots on the SUs and give them a mixture test by lifting the spring loaded pin under the lip of the pot after it warms up to see if they need to be set a little richer.

When it is at idle lift the front pin and if the RPM drops off and it sounds like an old John Deer tractor it is correct. If it speeds up and stays fast it is too rich. If it drops off and dies it is either too lean or the two butterfly shafts are not in sync.

When you lift the front pin you are checking the rear carb. (This is not the method written in most manuals) and when you lift the rear pin you are checking the front carb.

Howard