Jota 180 CDI ignition problems

PeteK

PeteK

New member
Location
Milton Keynes
On my way to a monthly club meeting recently, my 1978 Jota started misfiring and quickly worsened to running on one cylinder. I have done some checks and found that I have no spark on the two outer cylinders. The bike is standard with a Bosch CDI ignition (module with 3 integrated coils) and the Bosch cylindrical stop relay. I have done the following, but still same issue:
1. Flywheel removed and found insulation broken down on top pulse coil - repaired with heat shrink sleeving.
2. Checked voltage from charge coil (red wire) = 80VAC with engine cranking
3. Checked resistance to ground on red wire = 362 ohms (green book says 3000 ohms, but that seems high?)
4. Checked resistance of pulse coils (red/black to red/white = 58 ohms, white/black to white = 56 ohms, which seems OK (approx 60 ohms in green book). Test done at connector under tank with ignition on.
5. Same check as 4 above, but with ignition off shows short circuit on both coils, so stop relay working OK.
6. CDI removed and plug connections cleaned as far as possible.
7. Earth connection behind headstock checked with loop direct to battery negative.
8. New B8ES plugs, plug caps and HT leads fitted.
9. One strange result? I swapped the the pulse coil pairs over at the connector, to see if the fault would change to cylinder two, but no spark anywhere? Swapped back and spark returned on the middle cylinder.

I will take the flywheel off again and check the gaps on the pulse coils (forgot last time) and borrowing a scope meter to check the pulse coil outputs (anyone know what I should expect here?).

Once that’s done, I’m running out of ideas, so any suggestions greatly appreciated. I know the best advice will be to fit a new Sachse system, although having just retired, if I can repair my existing system, then plan the conversion later, I would prefer. Ultimately, I don’t do many miles on the bike and never at night, so the existing alternator doesn’t cause me any issues. Anybody, already converted and has CDI parts they would like to sell?

Thanks in advance, Pete K
 
Pete, ref checks 4,5 and 9.
My suggestion would be to isolate the stop/start relay. By-pass the relay and wire pick ups directly to the HKZ box. Test with plugs earthed (or battery negative before the guru corrects 😁) to the head. The old torpedo tandem relay is not the most reliable of components. If this is the cause, maintain the pick ups wired directed to the HKZ box and put a relay in the HKZ power feed wire. As I read your diagnosis tests, these have been done with all components still in circuit.
 
PeteK said:
I know the best advice will be to fit a new Sachse system

Thanks in advance, Pete K
Click to expand...

Sachse do not sell an ignition system for the Series 1 engines anymore since Volker died, you have a choice of the Witt or the Redax system for the Series 1 bikes
Redax system which is the one I make has the 250 watt x 3 phase charging system but try and fix your CDI if possible
Far cheaper
I have plenty of CDI kit in stock if you need bits, all used and as removed from bikes but am in Australia and postage costs these days is out of control

Looking at the tests you have already carried out you know what you are doing electrically so believe you will work it out
 
Pete, I have a CDI (BOSCH) from a 78 it should bolt right up, it is yours if you want it for the cost of postage, PM me. What you are describing is exactly what happened to me many years ago (mid 70's) while riding back from Melbourne to Perth. Just outside of an Esperance detour the CDI went on one (center) cylinder, tried everything to fix it, and was getting ready to find a farmer's backyard to park it in when I gave it one more try, it worked and got me back to Perth running on all 3. A week later it died completely, and Bosch in Melbourne replaced it for free (it helped to have a Laverda owner friend who worked for Bosch) The one I am offering you has never been used, I carried it as a spare in South America. Cheers Dave
 
FWIW, take up the very kind offers of redundant HKZ items, including any exciter coil(s), ( "Red" wire connection, 400Vac generator ). The small ignition coils are less than 1 Ohm primary resistance, actually reused these coils on my variant of a "HKZ" format, CDI for want of a correct term. Nice small coil, in the HKZ configuration, two primaries are in series, the centre coil obviously a single input output coil arrangement.

Should you have any ignition coil producing a spark, then the "Red" wire is ostensibly intact, plus or minus intermittent connection issues. Your correct to inspect the insulation of all wiring, especially the ignition coil primary wires secured to the metal frame work, seen this insulation cold flow and crack at the tie down partition.

Have repaired HKZ in the past, including replacing the internal SCR's, not a proposition these days, given there are fellow riders offering their never to be installed again systems. Carry a spare and off you go, have a warm spot for the HKZ, not so much Bosch as such, rather the quirky copper and iron nature of HKZ, and the bucking coil regulator, throwback to Mr Tesla era engineering.
HTH j.
 
Laverdian said:
Pete, ref checks 4,5 and 9.
My suggestion would be to isolate the stop/start relay. By-pass the relay and wire pick ups directly to the HKZ box. Test with plugs earthed (or battery negative before the guru corrects 😁) to the head. The old torpedo tandem relay is not the most reliable of components. If this is the cause, maintain the pick ups wired directed to the HKZ box and put a relay in the HKZ power feed wire. As I read your diagnosis tests, these have been done with all components still in circuit.
Click to expand...
Momentary open circuit of the 400Vac coil is not best practise, should i understand Laverdaian correctly, he is indicating a shorting to frame/battery negative then that is useful, as owner/rider have to decide if an active "short" or a fail safe mode, ie normally open contacts or normally closed contacts implemented. You will not damage the exciter coil with a short circuit, its output is "shorted" ie shunt regulated internally by the HKZ SCR that holds the maximum DC voltage to around 350Vdc for impression across the ignition coil primaries.

Mmmm, post here in order for hard won knowledge over the decades, to be, and is recorded, for reference and assistance.First principles applied at each opportunity, from those first principles and new age problems for old Laverda's, can be solved without a reinvented wheel being turned. Should i come across as pedantic, guilty, part of the process. In my electrical engineering classes, indicating to the students, a process of "how to learn", was not my job to "teach", for i could teach them what i know, and that is what they will only know.

Also taught in electrical trades, watching the young folk struggle with formula was heart rendering, was one of them once myself. Did "teach" the trade students, one technique, Transposition, remember one formula, and then derive the variant formula from that one basic retained in memory. Gave those challenged students a new tool, took only 30 minutes, yet relief was palpable on their faces and classroom well being. Never class myself, as guru, not even close, will as ever proffer first principles each time it has merit, apologies to the few whom find the technique an unwanted distraction. Wont be here forever, will be part of a solid foundation, better or worse, others can decide upon. HTH j.
 
I never tried remembering Trig Functions, why waste brain space when you can write it down for future reference? Good idea if you start with limited brain storage like me. Learning how to apply them is a different proposition
 
Many are the demands in a life, Vince, well we know, especially young minds, contending with much these days. Maths had the better of me, mainly Algebra, seemed illogical, more how it was taught in the day perhaps. Trig, loved trig, just worked for me, fascinating really, deriving distances and heights with only two out of three parameters... lucky me, j.
 
Ditto John, I loved Geometry and Trig. So pretty, elegant works better as a descriptor as to how it worked. Algebra not so much, with the exception of Quadratic Equations. Them I got. I think they missed quite a few rules when they taught me Algebra as every time I tried the target moved.
 
My dog can do quadratic equations. If I throw a ball, he can predict the parabolic flight path (solving the second order polynomial in his head in a fraction of a second) and then position his open gob in exactly the right place to catch it.

I quite liked maths at school and was reasonably good at it. I got put in advanced maths classes. Algebra and geometry were a breeze. Differential and integral calculus was OK, but I got out of my depth at university when Lapalce transforms appeared on the agenda. That stuff completely undermined my self-confidence in maths. I still have no clue what they're about. I can read the words, but they make no sense to me at all. I'm still emotionally scarred by my unmitigated failure to even get a glimmer of understanding.

Have a look at it. If it makes sense to you then you're a mathematical freak.

Laplace transform - Wikipedia

en.wikipedia.org en.wikipedia.org
 
78jotadave said:
Pete, I have a CDI (BOSCH) from a 78 it should bolt right up, it is yours if you want it for the cost of postage, PM me. What you are describing is exactly what happened to me many years ago (mid 70's) while riding back from Melbourne to Perth. Just outside of an Esperance detour the CDI went on one (center) cylinder, tried everything to fix it, and was getting ready to find a farmer's backyard to park it in when I gave it one more try, it worked and got me back to Perth running on all 3. A week later it died completely, and Bosch in Melbourne replaced it for free (it helped to have a Laverda owner friend who worked for Bosch) The one I am offering you has never been used, I carried it as a spare in South America. Cheers Dave
Click to expand...
Hi Dave,

Thanks for your offer. That would be great if possible? I think I have PM’d you, but not sure if it worked? Could you contact me by email on pete_kirkham@ btinternet.com
Thanks Pete K
 
redax5 said:
Sachse do not sell an ignition system for the Series 1 engines anymore since Volker died, you have a choice of the Witt or the Redax system for the Series 1 bikes
Redax system which is the one I make has the 250 watt x 3 phase charging system but try and fix your CDI if possible
Far cheaper
I have plenty of CDI kit in stock if you need bits, all used and as removed from bikes but am in Australia and postage costs these days is out of control

Looking at the tests you have already carried out you know what you are doing electrically so believe you will work it out
Click to expand...
Thanks. Any idea what I should expect in terms of signal from the pulse coils when cranking the engine. Seems to be about 250mV at the peak of the pulse, although both the same. One producing a spark and the other not? Thanks Pete K
 
Laverdian said:
Pete, ref checks 4,5 and 9.
My suggestion would be to isolate the stop/start relay. By-pass the relay and wire pick ups directly to the HKZ box. Test with plugs earthed (or battery negative before the guru corrects 😁) to the head. The old torpedo tandem relay is not the most reliable of components. If this is the cause, maintain the pick ups wired directed to the HKZ box and put a relay in the HKZ power feed wire. As I read your diagnosis tests, these have been done with all components still in circuit.
Click to expand...
Thanks for the reply. I hope to try your suggestion tomorrow. I’ll let you know how it goes. Thanks Pete K
 
Last edited:
Dellortoman said:
My dog can do quadratic equations. If I throw a ball, he can predict the parabolic flight path (solving the second order polynomial in his head in a fraction of a second) and then position his open gob in exactly the right place to catch it.

I quite liked maths at school and was reasonably good at it. I got put in advanced maths classes. Algebra and geometry were a breeze. Differential and integral calculus was OK, but I got out of my depth at university when Lapalce transforms appeared on the agenda. That stuff completely undermined my self-confidence in maths. I still have no clue what they're about. I can read the words, but they make no sense to me at all. I'm still emotionally scarred by my unmitigated failure to even get a glimmer of understanding.

Have a look at it. If it makes sense to you then you're a mathematical freak.

Laplace transform - Wikipedia

en.wikipedia.org en.wikipedia.org
Click to expand...
Do come out with gems the odd if not many times Cam, clever dog, catching a ball is a specialist calling, can he/she see without glasses...i cant.... a large smile here...j
 
hello Peter in Milton keynes, , I am a lot nearer than Red or 78JotaDave, I have a surplus HKZ unit with three mini coils, one of them has been interferred with, the wiring replaced (or some such) I cant recalm exactly, but since you seem to have a far better knowledge of electronics that i ever will, I am willing to give it to you, you can use it or rob it for parts, or even open it up, it will be yours, not bothered about postage, just send me your name and addes and its in the post. I do know that it was removed from a running bike, because it was me who remived it!
CLEM
 
CLEMTOG said:
hello Peter in Milton keynes, , I am a lot nearer than Red or 78JotaDave, I have a surplus HKZ unit with three mini coils, one of them has been interferred with, the wiring replaced (or some such) I cant recalm exactly, but since you seem to have a far better knowledge of electronics that i ever will, I am willing to give it to you, you can use it or rob it for parts, or even open it up, it will be yours, not bothered about postage, just send me your name and addes and its in the post. I do know that it was removed from a running bike, because it was me who remived it!
CLEM
Click to expand...
Thanks Clem

I have sent you a PM. Have you received?
 
Also you may like to inspect and measure the 5Kohm spark plug covers, presently installed, perhaps NGK of age indeterminate.

New, if able to secure the now rare NGK, 115degree variant, ensures some years of reliability for at least that vital component. HKZ have very fast rise time primary current. While not common, cross/misfire can happen, in the absence of correct covers.

HKZ will fire through a failing spark plug cover, much better than an inductive discharge type. Ditto the spike termination for 6m/m ( or 7m/m,cannot recall exact ) HT cable at the coil end. If not secure upon the spike, spark errosion of the termination causes considerable damage. Copper HT cable ( lawn mower shop ) applied only, no graphite/silicon HT cables, that type internal fractures on motorcycles HTH j.
 
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