Triumph Repair: 1973 TR6, john deer tractor, vacuum test

Question
Thanks for your time, I have SU carbs on my 1973 TR6, I think this just might be my problem? I am losing power when I am in first gear and all gears? I did have my TR6 sit in my garage for about 6 months so I changed my fuel filter. My TR6 starts fine and sounds nice but no power? please advise

Answer
Hi Joseph,
Yes, it can be the SUs along with about a hundred other items.

When a car is brought in to a dealership with such a problem we have to run tests and go through a procedure to get the engine running at it's potential.

First run a manifold vacuum test. Should have good vacuum at idle (20s) and it will drop as you raise RPM. If you raise the RPM up high and hold it there and the vacuum continues to go down, you should test for a partially stopped up exhaust system.

If that is ok, run a compression test (throttle open) (125 PSI to 160 PSI on all cylinders with little difference between cylinders)

Set the timing to specs.

Only after all that is done can you look to the SUs.
Did you drain the old gas out and put in fresh gas? After warm up and at idle lift the pin under the lip of the top pot to see what reaction is. If the engine dies you either have the throttle linkage between the two carbs not set right or the opposite carb is too lean. If the engine speeds up and stays fast the other carb is too rich. When it is correct the engine will drop down to a very low idle and sound like a an old John Deer tractor. check both carbs the same way.
Then confirm the oil level in the top pots.

When that is finished and a road test indicates there is still a loss of power especially under load or at speed you need to put a "T" fitting in the fuel line at the carburetor and check fuel pressure at idle and at sustained high RPM. (should be 1.5 PSI to 3 PSI)

Howard