Jerry, it sounds like you have covered all the bases except one. Check your
float
level in the rear carb (and front one too). It appears that you can not lean
out the rear enough,
possibly because the float level is too high.
If it is OK, try lowering it to artificially lean out that carb.
I have seen this sort of problem, and occasionally it is a REAL bear to fix.
In that one case
everything was looking fine, but it was lean. Raising the float level helped
somewhat...
Message text written by INTERNET:owner-triumphs-digest@autox.team.net
>From: jgoulet@finning.ca
Subject: IS THERE AN SU CARB DOCTOR IN THE HOUSE?
I have been tuning the engine of my TR3A over the last few
weekends and have run into a puzzle.
The engine runs rough during idle and also there seems to be
less power, so I tried the test of pulling a spark plug wire one at a time
while the engine was idling (1200rpm).
Cylinders 1 & 2 both caused speed loss as expected but
cylinders 3 & 4 both caused no change when their leads were pulled out.
I have swapped cap and plug wires with a spare set with the
same result.
Wires are connected 1-3-4-2 going counterclockwise on the
cap from the first pointed a plug one.
I have swapped the plugs 1 - 4 and 2 - 3. Yet cylinders 3 &
4 do not seem to have fire even though they have spark and fuel.
I cleaned and gapped the plugs at 35 thou....there is a
sport coil (40000 volt)
The plugs were sooty black, worse on cylinders 3 & 4.
Also, I have balanced the SUs with Unisyn and leaned them
out as far as they will go, but the rear SU (for cylinder 3 & 4) still
causes the rpm to rise and stay up when the lift pin is pushed.
The valves have been set to 10 thou.
Compression test shows about 140 psi in each hole.
Could the rear SU cause this?
Can you suggest any more tests?
Jerry Goulet
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