Listers,
I'm going mad. Mad I say. My mostly stock 76 TR6 has a bad case of
stuttering on acceleration. Almost any kind of acceleration, it stutters,
sometimes backfires at carbs, has popping noises at the exhaust on
deceleration. It starts fine, idles fine, then gets bad as it warms up. When
cold, it behaves itself but quickly gets bad as the engine warms up. And -
it's not always this way. Sometimes is runs just fine for a few minutes, then
goes bad. I've got the timing at 12 BTDC, vacuum retartd disconnected and
plugged. I can usually make it driveable by puching t he timing to about 25
BTDC (!) but it still sounds like it's either missing or sputtering. And
often the carb bores are very wet with gas. So I went around and around going
between carb and ignition. I may have to enter an institute for the
criminally insane. In all of this, after every turn, the manifold vacuum at
idle is a fairly steady 17 mmHg. That sounds good, doesn't it?
Here's what makes no difference, in no particular order:
ignition: swap plugs, wires, cap, rotor, points/condensor, coil I eve
ntried changing the distributor/oil pump drive gear by a tooth (no fun to
ensure that the oil pump is propely located). I did notice somthing odd here
- the rotor position, just as the points break, is about 10 degrees before the
rotor aligns with the #1 stake on the dist cap. So advancing the ignition
brings it closer but then the timing is, well, advanced and it still sputters
a little. Also I have a few caps and rotors but only one combo really makes
it work ok. That sounds weird and I wonder if anyone else has had such a
sensitive cap/rotor combination.
.....and still more that makes no difference:
carb: ended up rebuilding the carbs - pretty much everything including
throttle bypass valves (not temp compensators), diaphrams, floats, needle/seat
(regular, not Grosse) spindle seals, etc. Still the same problem. What
could it be? I'm wondering about the float height. I used 16 mm for the
distance from float bowl to highest part of float. At that time the floats
are not level but the setting is to spec I think. 16 mm is about 5/8" is that
ok? I'm suspicious because of the wet carb bores after a run. Is it worth a
shot to increase that distance and thereby lower the gas level in the bowl?
Or has anyone had this problem before? I apprecaite in advance any help from
the wisdom of the list.
George Loriot1976 TR5
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