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Discussion Starter · #1 ·
Hello
my cm 400 t had the change of the hondamatic in prize.
Super acceleration, torque and higher power, but I have an excessive noise at 1200 rpm ... the minimum is accompanied by a clan.clan.clan.
At high rpm there is a hissing sound like in the turbo compressors
I replaced the converter with another used but the noise is the same.
The engine running without a converter is very quiet at all speeds.
Castrol oil 20/50 ..
How can noise be reduced to a minimum? Help help
Greetings from Italy
Orazio
sorry for my google English
 

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Discussion Starter · #2 ·
a greeting to the Friends.
I have analyzed the components of this wonderful motor to find the noise caused by the torque converter of my CM400 T / A.
1) my CDI at the minimum regime has an advance of 15 ° and not 7.5 ° as the matic.
Can this excessive advance result in excessive vibration of the drive dampers?
How many of you have had experiences around the torque converter?
Thank you for the answers
Orazio
 

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That is a lot of advance at low rpm, and many engines will make more noise/vibration. Can you adjust the position of the sensor that signals the ignition module when to send the spark?
 

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Discussion Starter · #4 ·
That is a lot of advance at low rpm, and many engines will make more noise/vibration. Can you adjust the position of the sensor that signals the ignition module when to send the spark?

Unfortunately, the sensor can not be moved.
The displacement of the advance is done automatically by the certraline CDI. My CDI (CM 400 T) moves from 15 ° to 48 °.
The CDI of the CM 400 A moves from 7.5 ° to 15 ° and then 48 °.
At the moment I would like to understand if the noise depends on this unit or another reason.
Only you experts can help me ...
In Italy there are no experiences on this engine.
Greetings
Orazio
 

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The timing advance has to have a reference pulse, to tell it where the engine is in its rotation; the ignition uses this reference to determine when to generate the spark, and how fast the engine is turning, to increase or decrease the advance. There should be some kind if sensor near the crankshaft or flywheel/rotor, that sends this pulse. Sometimes, that sensor can be adjusted; many times, it is fixed. Your new converter could have a small magnet on it, which passes the timing sensor, and its position could be what changed the base timing. If you can look at your original converter, you may find a magnet on it; it may be located 7.5 degrees from where the one on the new converter.

Anyway, 15 degrees advance is fairly high on an engine designed for 7.5 at idle, which could be the source of the noise. The spark coming too early can result in a brief pre-ignition, or knock, because the explosion comes before the engine is close enough to top dead center, and briefly tries to turn it backwards.
 

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Moved to SOHC Engine section
On the A model the timing is at 7.5* BTDC in neutral only. Once the transmission is engaged the timing is advanced to 15*. This functions as an idle compensation for the drag applied by the torque converter.
The bang type noise at low rpm may be the balancers bouncing internally due to worn insulators. When you changed oil did you find small bits of what seems like black plastic?
Not sure about a hiss noise, maybe someone with an A model can give some information.
 

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Discussion Starter · #7 ·
È vero , il motore in folle gira a 7.5 e in prima marcia passa a 15...la conferma la attendiamo dal signor Steve9e che possiede due hondamatic .Appena ci legge , ci dirà il suo parere.
 

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Steve9e who has two hondamatics is going to help him. Thanks, Steve.
 
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