A question for motorbyce freaks

[Boncuk]

A friend of mine owns a Honda Magna 750 and asked me to build a "CANCEL UNIT" for him.

All he has on hand is a complete electric wiring diagram of the byce and a brief introduction about how to connect the device.

I guess the cancel unit is necessary to keep cylinder head temperature within limits at (tropical) high ambient air temperature.

I'd appreciate any description (possibly a circuit schematic) of the device on behalf of my friend. (The byce is 30 years old and supposedly no more cancel units are manufactured for it.)

Kind regards

Boncuk

 

[cr0sh]

"motorbyce"..."byce" - is this some kind of slang where you live? Does it mean "bicycle"? As in "motorized bicycle" - or is it more like "motorcycle" (aka "motorbike")?

I mean, I am pretty sure you are meaning some kind of motorized 2-wheel device, but it could be anything from a motorized bicycle to a moped, to a full-sized Harley...

??? LOL ???

 

[Boncuk]

"motorbyce"..."byce" - is this some kind of slang where you live? Does it mean "bicycle"? As in "motorized bicycle" - or is it more like "motorcycle" (aka "motorbike")?

I mean, I am pretty sure you are meaning some kind of motorized 2-wheel device, but it could be anything from a motorized bicycle to a moped, to a full-sized Harley...

??? LOL ???

Blame it on the language barrier.

Anyway it doesn't answer my question at all.
lol lol

BTW, I wouldn't call a 750cc motorbike a "moped".

 

[cr0sh]

Blame it on the language barrier.

Anyway it doesn't answer my question at all.
lol lol

BTW, I wouldn't call a 750cc motorbike a "moped".

Ok, ok; fair enough - but what is a "cancel unit"? Is this its actual name? How does it work? I'm not seeing much of anything relating to engines when I google the term (I get plenty of hits for something to do with turn signals)...

 

[BrownOut]

I tired googling too, and all I came up with was a turn signal cancelling unit. Maybe that's what this is all about???

 

[Boncuk]

I tired googling too, and all I came up with was a turn signal cancelling unit. Maybe that's what this is all about???

As far as my information goes the Honda Magna 750 is fitted with extra coils in the HV cable of each cylinder (4) for a stronger spark. The spark plugs do not look like the usual ones with a center electrode and a hook shaped ground electrode, but have a ring of ground electrodes.

A stronger spark also means higher combustion temperatures which might lead to cylinder head over temperatures at high ambient temperatures and a lean fuel-air mixture. (in Thailand up to 46deg/C (115deg/F) during the hot season)

To avoid this the cancel unit shorts out the coil for a weaker spark. (There is no device to control fuel-air mixture like it is used with piston type aircraft engines.)

Thanks for your replies anyway.

Regards

Boncuk

 

[BrownOut]

Sorry I can't be more help

 

[HiTech]

So it appears as if you need a temperature sensor of some sort (be it thermistor or bi-metal contacts) to trigger a relay or solid state switch which in turn shorts the primary of an ignition coil. I gather the sensor would get mounted to the cylinder head.

What perplexes me is in all of Honda's infinite wisdom and engineering excellence, why would the engrs. choose to switch off combustion efficiency and performance? They could have designed the head out of better material as well as fix a lean fuel mixture with an ECM (engine control module). Modern diesels and Top Fuel dragster motors have engines that are running way hotter temps than a street bike and the heads aren't failing along with lean-burn mixtures being a concern.

 

[Boncuk]

Hi HiTech,

you might have missed the fact that the motorcycle is more than 30 years old. I'm sure technical know how wasn't that high level when it was built.

Further, not the primary side of the ignition coil has to be shorted (which is done within the ignition distributor already), but the extra coils in the HV cable - one for each cylinder. Shorting out the coils the combustion is still satisfactory without causing smoke - with just a minor loss of peak power, hence efficiency.

I also guess a dragster engine requires a complete overhaul after a race.

My friend has worked it over completely and it looks like new. He's just a bit worried driving it at those high ambient temperatures in Thailand.

Boncuk

 

[shortbus=]

As far as my information goes the Honda Magna 750 is fitted with extra coils in the HV cable of each cylinder (4) for a stronger spark. The spark plugs do not look like the usual ones with a center electrode and a hook shaped ground electrode, but have a ring of ground electrodes.

A stronger spark also means higher combustion temperatures which might lead to cylinder head over temperatures at high ambient temperatures and a lean fuel-air mixture. (in Thailand up to 46deg/C (115deg/F) during the hot season)

To avoid this the cancel unit shorts out the coil for a weaker spark. (There is no device to control fuel-air mixture like it is used with piston type aircraft engines.)

Thanks for your replies anyway.

Regards

Boncuk

The energy of the spark has no measurable effect on the temperature of a engine, The same as the temperature range of a spark plug does not change the temperature of a engine.

Yes Top Fuel engines and even the clutches are rebuilt after each run.

Ther are several Magna forums, maybe ask the question there?
https://www.google.com/search?q=hon...fDiKSuAQ&ved=0CIYBENUCKAU&fp=ea5733a97aebfa72

 

[Boncuk]

The energy of the spark has no measurable effect on the temperature of a engine, The same as the temperature range of a spark plug does not change the temperature of a engine.

Yes Top Fuel engines and even the clutches are rebuilt after each run.

Ther are several Magna forums, maybe ask the question there?
honda maga 750 - Google Search

Hi shortbus=,

thanks for your input. Even if cylinder head temperature is almost not affected the spark plugs might get beyond their temperature limit.

I'ts not advisable to stop a vehicle on country roads (neither intended nor unintended) in Thailand.

You might end up with your head chopped off by a machete while repairing the motorcycle - which will ruin your day.

A neighbor's husband got shot off his motorcycle in the canyons near Chiang Mai to rob him for a few Thai Baht.

I'll check out the link you gave me.

Thanks again.

Kind regards

Boncuk

 

[atferrari]

What a choice of a country you did, Hans!

I will be happy (or surprised?) the day I will hear you to tell something good from there. Maybe you cannot...

Are you happy living there, after all?

 

[shortbus=]

Boncuk - These bikes use a water cooled engine, is it possible that the unit you a asking about is a aftermarket add-on? Maybe a intermittent water spray to cool the radiator when temperature gets too high. These bikes are known to run hot.

Here is Honda site for free downloads of service manuals. Not knowing the year you will have to look it up your self. Maybe the unit will be in the manual. **broken link removed** Hope this helps

 

[Boncuk]

Hi shortbus=,

I downloaded the service manual and went through all 223 pages. There was nothing to find about a cancel unit.

I'll ask my friend to contact a German club for more info.

Regards

Boncuk