John,
Did you rebuild your carbs as part of the engine rebuild? If you did
rebuild them and replace the needles and jets, how deep in the carb
throat did you locate the jets?
I had a similar problem caused by the PO when I first purchased my TR6
9 years ago. The PO had rebuilt the carbs and had installed new jets
even with the throat of the carb. In doing my research and ordering
the parts to rebuild the carbs from Apple Hydraulics, I asked how deep
the jets should be installed. I was told that when Apple rebuilds
carbs they install the jets 85 to 120 thousandths below the throat
surface. I got out my dial indicator and installed mine at about 100
thousandths. When I reinstalled the carbs, my problem was solved as I
could now adjust the richness enough to make it run properly. With the
jets installed even with the throat body, there was not enough
adjustment in the needles to get the richness required to keep the
backfires from happening. Even if you didn't rebuild your carbs, those
jets may not me deep enough in the throat with the GP2 Cam for the
needle adjustment to get you rich enough. Long shot, but thought I
would mention it in the event if works for you.
John Shewmake
'74 TR6
Chattanooga, TN
-----Original Message-----
From: John North <johncnorth@gmail.com>
To: Triumph 6 Pack <6pack@autox.team.net>
Sent: Mon, 4 Aug 2008 7:24 am
Subject: [6pack] Missing under load
Tuning following my engine rebuild... When I put the pedal to the
floor in any gear, the engine misses badly, and smooths out when I
back off the throttle. This is especially true at 2000 rpms or less.
Once over 2500, it accelerates pretty well, still misses
occasionally.
I have 9.5:1 compression, Goodparts GP2 cam, smoothed ports. I am
running with stock ZS carbs.
I have checked timing, points, plugs multiple times. Have advanced
and retarded timing a few degrees. Replaced wires, rotor, dizzie cap
with known good ones. Changed carb needles for B1E. All these with
little effect. Dashpots have 5/20 oil in.
Vance called the GP2 a hairy cam, as I recall, and I am starting to
wonder whether that might be the issue. Maybe it needs to run over
2500 rpms...
Any other experiences out there or suggestions for where to go from
here?
John North
6pack@autox.team.net
http://autox.team.net/mailman/listinfo/6pack
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