.::YAMAHA::. | ||
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YAMAHA RD 350
ALL YOU WANT TO KNOW.....! |
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Advance = the amount of
angular measurement that the spark happens before the piston reaches
top dead center (TDC) on the power stroke.
Retard is less amount
of advance
Internal combustion
engines need to start the combustion fire before the piston reaches
TDC because it takes an amount of time to get the gases burning. The
spark happens before TDC, this is called BTDC. If you don’t start
the gases burning BTDC a lot of the energy will be lost. Obviously
making the burn happen at the right time is important in the
production of power.
Many automotive engines
have a mechanism to change the ignition timing as the revolutions
per minute (RPM) goes up. The faster an engine turns the ideal time
of ignition varies (the faster it turns the more advance is needed).
Yamaha RDs do not have an ignition advance mechanism. Some
automotive engines have mechanical advancers and some have
electronic advancers. Your bike has neither. The specification from
Yamaha is that the ignition happens at 2.00 MM BTDC. They could have
said 19 degrees of crank angle but that is harder to measure. You
would need some kind of degree wheel attached to the crank to
measure degrees. With a dial gauge you can measure 2.00 MM BTDC,
which is a very good substitute for angular measurement.
So how do I time the
bike??????
If you have a dial
gauge you use it to make sure the ignition marks on the rotor and
stator window line up at the time you want ignition to occur. If you
do not have a dial gauge, I guess you have to trust Yamaha that they
manufactured the bike with some quality controls in place and the
marks are at least close to correct. Before you attempt timing you
need to make sure the ignition points are set correctly. Why?
Because the coils need a minimum amount of time to saturate (gain
full charge). The manual suggests a point gap of 0.3mm. Make sure
the points are all the way open before measuring and adjusting and
make sure they are clean. Wipe them when they are closed with a
white business card (you know the kind that a businessman has with
his name and address on it). When the points are closed, open the
points with your finger and insert the card (.25mm white card stock
will work) close the points and slowly remove the card without
tearing. Do this until the points leave no mark on the white card
stock. Timing the bike you want the points to open at exactly the
same time as the timing marks come into alignment. If you have
timing light this is easy to do. But in case you don’t have a timing
light you can use an ohmmeter to do the same thing. Hook up the
meter and watch it and the timing marks at the same time. As the
marks come into alignment the needle on the meter should swing from
0 ohms to infinity ohms. Oh you don’t have an ohmmeter?????????? Try
this little trick; the ignition switch needs to be turned on for
this trick to work. What you do is hook up a small light bulb (12V)
to the ignition points as one connection and positive terminal of
the battery as the other. The points are closed sending electricity
through the condensers to earth, hence the bulb doesn’t light up.
When the points open the coil fires and your bulb lights up at the
same time. You want your bulb to light up as the timing marks align.
Simple?
Timing…the next
frontier. Since you do not have an advance mechanism on your RD you
have to chose a number and live with it. 2.00 MM will be OK both top
and bottom. You have to decide what is best for you. Be careful
about advance. Some gasoline works better than other gasoline. Some
like advanced ignition timing(93 octane and more), other gasoline
does not like advanced ignition timing(87 octane). Hence if somebody says retard your timing they mean make it fire closer to TDC or with less advance. .::BACK::. |
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