500cc ignition system

Lyndoneil

Lyndoneil

Full member
Location
Towcester uk
I'm having trouble getting a decent spark at my plugs and hence starting problems, not made easier with high comp pistons and high lift cams, have shortened the ht  leads to good wire,  have not checked the coils yet apart from making sure all connections are good, as it does not appear to be that easy a task for some one that is not actually an accomplished auto electrician,  but  I have seen on other threads relating to the triples and 750s that the ballast resistors on the coil low tension leads are not necessary and can be removed to increase the voltage to the coil. Would this be applicable to the 500s too, I've removed them at the moment and the spark seems brighter, but don't want to damage the Bosch control boxes.
 
Yep, ballast resistors can safely be dispensed with.

Carefully check and clean every connection in the ignition 12v wiring, including switches and earths. Don?t forget battery connections and also well worth servicing the starter motor.  Objective is to minimise voltage drop wherever possible.
 
If you have the original ignition system it will require the best possible voltage to get at least enough high voltage energy to fire that engine, they are no different to the ignitions for the triples of the time any voltage drop and your starter will chew up the bulk of the power required to fire the engine.
 
Rob said:
Yep, ballast resistors can safely be dispensed with.

Carefully check and clean every connection in the ignition 12v wiring, including switches and earths. Don?t forget battery connections and also well worth servicing the starter motor. 
Click to expand...

Also the fuses and fuse-holder contacts.
 
Thanks guys.
Will try anew, ditch the resistors,  and methodically clean every thing.
Its not as if I can go anywhere else.
I have the carburator adjustments to make, and want to set up the ignition timing.
It's towards the end of a long and increasingly expensive rebuild, I'm almost at the point where I'm thinking I should have threw the original bike in a skip, then brought all the individual bits  from the likes of Wolfgang and Richard Slater and assembled them together. Probably would have been quicker.
 
Rob said:
Objective is to minimise voltage drop wherever possible.
Click to expand...
+1.

The only risk you run when ditching the ballast resistors is of the coils heating up once the bike is running and full voltage is being supplied to the coils.

But:
a) This isn't really your problem at the mo', is it?  :D

b) It's a risk that is probably more theoretical than real.  Bosch/Nippon Denso were playing safe ...
 
first step is to remove the battery terminals (both ends) and scrupulously clean everything that bolts up and reassemble with a bit of Vaseline for anti corrosion, but after you have bolted all up tight, then proceed as Rob advises, I would even remove the battery from the bike to clean the terminals, use a fine file, and make everything shine, wear shades.
CLEM
 
Rob said:
Not true!!  Bosch were 'playing safe' but the coils are rated at 12v.  The ballast resistors were specified by Bosch to guard against the BTZ boxes being inadvertently destroyed by non-standard HT impedances.
https://www.laverdaforum.com/forum/index.php/topic,85578.msg216329.html#msg216329
Click to expand...

Ah yes, I had forgotten John's rather ..  convoluted alternative explanation  :D.  Whatever ... the end result is the same: yes, you can safely remove the ballast resistors  ;)
 
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