Steve:
A guess would be 400 RPM cranking speed. But I would expect it to start
even
if the cranking speed were, say, 300 RPM or less.
Some things to check:
1. Spark plug gap. They should be around 0.025" or so. Make sure they
are all
correct.
2. Cap and Rotor. Make sure you have the correct rotor and cap for your
model
year. The design changed during the production run, and you cannot mix and
match the cap/rotor. Also inspect the inside of the cap to make sure there is
no damage and that the cap is clean inside. Inspect the rotor for any damage
as well.
3. Firing order. Make sure your wires proceed ANTI-CLOCKWISE around the
top
of the dizzy cap in the following order: 1-5-3-6-2-4.
4. Spark plug wires. The wires are resistor wires, and can go bad. If a
plug
is not firing reliably, try swapping a wire from a cylinder that does fire
reliably. If that solves the problem for the bad cylinder, replace the plug
wires. You can get wires from any good auto parts store. Bosch makes a set
that will fit.
5. Timing. Surprisingly easy to get wrong. Set the timing at 10 BTDC
with the
vacuum line to the dizzy disconnected and plugged. The shop manual is
confusing and a failed vacuum pot will give a false reading, so this is the
safest way to get the correct result.
6. Dwell (or point gap). Make sure the gap on the points is correct, or
better yet set the dwell using a dwell meter. If this is wrong, the points may
not open or close fully and missing sparks will be the result.
7. Spark coil. Make sure you have the correct coil. High performance
coils
draw more current and if your battery or wiring is marginal, may cause
problems. I do not recommend the use of high performance coils, although many
people have great success with them. Check the resistance of the primary side
of the coil. It should be about 3 ohms if you have a stock coil.
That will keep you busy for a while. If that doesn't do it, let us know
and
we can start talking about the carbs and/or cam timing.
Vance Navarrette
Cogito Ergo Zoom
I think, therefore I go fast
-----Original Message-----
From: 6pack-bounces@autox.team.net [mailto:6pack-bounces@autox.team.net] On
Behalf Of Stephen Lindquist
Sent: Monday, December 15, 2008 12:00 PM
To: 6pack@autox.team.net
Subject: [6pack] Proper starting rpm
What rpm should the engine crankshaft be turning at when the starter is in
good shape and the battery fully charged?
I am trying to diagnose a lack spark to my plugs. I get a nice spark off
the coil if I attach a plug wire to the coil output but not all spark plug
wires seem to be firing at 1/6th of the coil spark rate. And since the
engine wont start I am trying to diagnose the problem from starter
rpm/camshaft rpm and the numbers don't seem to make sense.
68 TR250
Thanks, Steve
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