That is a different problem than I have had.
I can't get the Digitron to properly register the EGT's.
This past weekend at MidOhio (interesting new surface) the only readings I was
getting were about 1800-1900F. Oddly, there wasn't a puddle of metal sitting
there and actually was able to pull the Fords on the start and kept going.
Freshly rebuilt Digitron DT54 will be freshly rebuilt again.
I don't know what the EGT really is, but the plugs are pretty wet still with
the recommended Tony Murphy settings.
I think this engine dumps more unburnt fuel into the manifold where it is
burning.
jim
----- Original Message ----
From: Ted Rudolph <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Sent: Monday, July 3, 2006 12:19:19 AM
Subject: [F500] (no subject)
Anyone else having trouble tuning a 493? Can anyone give any insight into
properly tuning one?
My engine (new from Tony Murphy in 2004) was running pretty well last summer,
although at the last race of the season (the Fun One at the Glen) the PTO
cylinder did not come up to temperature as quickly as the Magneto side. If we
let the engine run for a few minutes, did a lap around the paddock & then
changed the PTO spark plug the engine would run fine. Once we finished out
warm-up procedure it would run great - in fact, it was very fast all weekend.
We didnt do anything over the winter except remove the balance tube and plug
the holes. This year at the Pocono Double the engine was a bear. Same
problems getting the PTO cylinder to come up to temperature, although changing
the plug after warming didnt help things. The PTO plug would be wet when it
came out, while the Mag plug was a nice milk-chocolate brown color.
During the first on-track session, the Magneto Cylinder temp would spike high
(1500) at full throttle, while the PTO side would drop to nothing. If I
breathed the throttle a little, the cylinders would drop back to normal
(although the PTO was still low 800-900 degrees vs. 1200 on the Mag side).
Between sessions we went to richer jets the only ones available were 340s
(thanks again to Steve Moore!) instead of the normal 290s. It ran better in
the afternoon on the bigger jets, although a bit cool (EGT) and it certainly
lacked top-end power.
Next morning we moved the needles (stock needles) to lean the engine back a
touch and it ran better at the start of the race, but after five laps behind
the pace car it was loaded up and took the last two green laps to clear out
but boy did it feel fast on the cool-down lap.
At Pocono we tried swapping the Carbs, the plug wires from the coil, swapping
the reed valves and swapping the rubber carb flanges/reed covers (all from the
PTO to the Mag side & vice versa). None of them fixed the cold PTO problem.
Likewise, we also did a compression test both cylinders showed 120-125, so
they weren't totally out of whack.
Anyone have any ideas? All that seems left is the actual cylinders or the oil
circuit (too much oil fouling the plug? Can it become unbalanced on one side?
Ive read the Mikuni manual and it hasnt helped any. Is there a better
2-stroke tuning/performance book available?
Thanks,
Ted
#98 Raptor, NE Div
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