Interesting result from Sachse igintion - did I install it wrong

C

chrissoz

Senior member
Location
Sydney, Australia
On my 750SF1 recently replaced points with Sachse ignition. All went well and the bike is running much better. However...
... I have noticed a couple of times when putting the ignition key in but not touching any other controls there is a bit of noise from the engine, sounds like I have just tapped the starter button. Yesterday when I put the key in there was a puff of smoke from the carbs!

I was scratching my head about theses two rather odd occurences when it came to me - I popped a plug cap off, put the key in and Lo and behold there was a single spark after about 3 sec. What I think is happpening is that during the boot up of the electronic ignition it is producing a spark which is causing the small amount of unburnt fuel in the chamber to ignite, if the inlet valve is open this produces a puff of smoke, if not then it moves the engine a bit causing a bit of noise from the starter clutch.

Is this expected? I wired the +ve side of the ignition to the indicator fuse (as the bike has no indicators and it was a much shorter run than connecting it to the +ve supply for the coils), could this be the cause.
 
Toying with the idea of fitting a Sache to the SFC and getting it club rego so I can ride it more. I'm interested in how the 750 runs with it.
What do they roughly cost?
Sorry can't help with your question but your conclusion sounds feasible.
 
750 seems to run much better with it, starting is certainly easier and it seems to pink less at low revs. I have not managed to do more than town riding so far though. Fitting was pretty easy - did the whole positive stop/degree wheel thing but came to the conclusion that the factory TDC mark was pretty much spot on.

I bought it from Red - he can give you pricing  - and good service! Turned around a defective unit for me in <24hrs!
 
chrissoz said:
On my 750SF1 recently replaced points with Sachse ignition. All went well and the bike is running much better. However...
... I have noticed a couple of times when putting the ignition key in but not touching any other controls there is a bit of noise from the engine, sounds like I have just tapped the starter button. Yesterday when I put the key in there was a puff of smoke from the carbs!
Click to expand...
could be that switching on power on an electronic ignition there is a spark on all plugs... happened on a Duc Pantah in my garage. No influence on running behaviour though :D
 
could be that switching on power on an electronic ignition there is a spark on all plugs... happened on a Duc Pantah in my garage. No influence on running behaviour though
Click to expand...
Had this happen with an electronic ignition /Piranha/Newtronic) on my Guzzi Lemon.
Didn't do any harm.

Ernesto
 
motoddrob said:
Toying with the idea of fitting a Sache to the SFC and getting it club rego so I can ride it more. I'm interested in how the 750 runs with it.
What do they roughly cost?
Sorry can't help with your question but your conclusion sounds feasible.
Click to expand...


  They run very well indeed with a Sachse Rob, get one and fit it, you will fall in love all over again.. ;)


    Keith
 
I am not too worried about it now - when the smoke was coming out from under the tank I thought it was a major electrical problem and ripped the side panels off in the street to see what was on fire. When I realised it was coming out of the air filters I was just mysified. Now I am just glad I know what was causing it.
 
Hello Lads,

Unintended  spark in electronic ignition,  is something designers of these systems can struggle to control.  Engine running ( hot ) already condition and ignition off is ostensibly not a problem,  ie there will not be a spark produced at incorrect timing point. Even if it did occur there is little chance it will ignite at the worst time.

  However ignition power up is a different case,  dependent on design of the control system, unintended spark at power on is,  and can be a problem,  that does not solve with ease.  Ignition module control Reset and Initialisation states can be such that in an inductive discharge system,  one or more coils are saturated and at reset of control board,  the coil is turned off ie a spark occurs no matter the position of the crank.  Hope i make sense so far.

  At this time i know the DMC systems are not prone to unintended spark at power up,  though it is possible with a flame out after a cold crank and initial running engine,  ie the DMC resets the control system after flame out.  If a coil was saturated at instant flame out occurrence  ( Crank stopped ) it will initiate a spark when the coils is reset to the off state.  Sometimes evidenced as a small crank turn or back fire from the inlet system.  BTW that is the  much loved BTZ characteristic of massive backfires on 120 engined bikes,  the BTZ dumping the saturated coils under cold crank battery voltage sag.  One time i was asked to include this "feature" on the IIS for party trick times,  scaring the hell out of women and small children... know it spooked me when i first heard and witnessed this "feature".

  Back to the cold start spark,  know i worked hard to overcome the well known unintended sparking issue.  More so when i had a crank flick back on me while a large spanner was attached to the crank,  nearly broke my hand,  extreme case i know, yet it was a concern that had to be mitigated on any supplied IIS either TA ( inductive discharge ) or TCI  ( Capacitor Discharge system ).  Was tackled at the design level,  there is little choice.

  There are many conditions that can lead to any ignition providing an unintended spark,  no one maker has it beat 100%.  There is always the possibility that the condition is engine specific like others mention,  ie not an intrinsic design issue,  worked on many other electronic ignition systems over many decades.  MSD, to Piranah, to Boyer, to Lucas Rita,  factory electronic systems,  you name it i have worked on them.  Some have unintended ignition spark  and some do not,  it is a legislated rule in Europe at one time that made it an illegal operation on motor vehicles,  ie no spark at engine ignition on no crank.

  HTH John. 
 
My DMC2 will flash the spark plugs when turning the ignition on. Never a problem. Had several Rita systems on various machines that did the same. My BMW R75/5 with a Rita would give an engine "chug" from time to time when the ignition was powering up. The 3c has yet to do that with the DMC.

Just checked to see if the spark plugs flash when the ignition is turned off..no, only when the DMC powers up.
 
Waiting for my RGS to actually start when I turn the key! 

With the currently fitted low-resistance coils and special software on the DMC II, a BIG FAT spark on booting has become quite normal.

Any modern digital ignition is a giant step forward for any points equipped bike, Lavs being no exception.

piet
 
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