John---Does the A/F monitor show full rich only at idle speeds? If so, does the
monitor then recover into the rich area after rpm picks up? I need this info to
give more help! Meanwhile, I'll just guess as to the problem and possible
solutions.
a) The air valves are flying open because the oil in the dashpots is too thin.
b) The springs that help to keep the airvalve from coming up too fast are
either missing or weak.
c) One carburetor is running too lean, but the monitor is sensing richness
because the other one is too rich. (Measure the diameter of the needles right
where they exit the air valves. They should be identical.
d) While the needles may be too rich at idle, they are not thin enough just off
idle. (Your monitor is showing you the lean condition)
e) Be sure the ign. timing is advancing and following the engine speed.
There could be other problems, but making this list longer won't "get it
through"!
Dick
-----Original Message-----
From: John North
Sent: Monday, May 31, 2010 4:35 PM
To: Triumph 6 Pack
Subject: [6pack] Carburetor problems?
When I floor it at fairly low rpms, the engine coughs and splutters.
Very embarrassing in the auto cross. I have a K&N O2 sensor system
installed, it normally shows quite rich (2 green bars), but when I
floor it it goes to full lean until the engine recovers. Timing is
spot on, valves adjusted, gaps and points set, distributor rebuilt,
new rotor, new wires. Have swapped out the coil. Carbs are
balanced and set to mid range mix - two full turns from full rich,
doesn't seem to make much difference where they are set, O2 sensor
still shows well on the rich side and the engine stumbles horribly.
Dashpot oil filled.
This is a 76 with all the smog control equipment removed. 9.5-1
compression, mild porting, Good GP2 cam
Any suggestions?
John North
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