Bosch CDI ignition control box

Lyndoneil

Junior member
Location
Towcester uk
This is a very tenuous Laverda question, actually barely Laverda at all, but you're a bright crowd, so I'd sooner ask here than elsewhere.
I believe I know the answer to my query, but would value clarification.
I have a Montjuic on which I have replaced the Bosch ignition with a Sachse ignition system, thus I now have two Bosch ignition modules.
I also have a Ducati 500 Pantah, which has a ignition problem around the 4000 rpm range, it back fires, hesitates and momentarily cuts out, fine if I power past that range, or change down to keep the revs up, but it gets tiring riding like I am on a race circuit all the time.
I changed the pickups on the Pantah a few years ago, made little difference, also the problem seems to be getting worse.
The Bosch ignition modules 1217 280 034 are identical on both bikes, so presumably it will just be a case of replacing them with the ones off my Monty, to see if that is the cause of the issue.
The advance/retard seems to be the cause of the problem, which I guess is controlled by the Bosch CDI box.
 
Yes, and there is a typical sudden one-step jump to full advance. They suffer from breakdown of ignition wire insulation from hot oil as well. Give the swap a try, but be careful, nice and steady with a few plug checks. Look for salt and pepper deposits on the plug, that's bits of piston. Melting pistons isn't fun. BTW that's 500s, and 600s the 650s came with a Japanese ignition, forget its name but it started with a K, something like Kusarni? that had 2 advance steps.
 
Advance/retard is also controlled by the pick-up/rotor gap. The gap determines when exactly the advance jump occurs, if it is uneven between the cylinders, a certain amount of jerkiness can be expected.

Don't know from where exactly the Pantah rotor is driven, but if that shaft is bent or its' bearing/bush has slop, gap will surely differ.

If the box is knackered, a/r usually won't occur, they usually remain stuck at full advance and don't retard at all. Other than a completely dud box, that's about all that goes wrong with these things. At least this won't kill your engine... just somewhat inconvenient at start and idle.

piet
 
Me and a smarter other bloke played around with my Pantah pickup gap trying to fix a sudden poor power off idle thing, I had been repeating stuff for ages trying to fix this and changing that gap was a hail mary move. I had to take off from traffic lights like an over-geared 2 stoke, it was a pain to ride it like that. Eventually fixed by discovering my fuck up. The carbs were out of sink by 5mm or more. I was using vacuum gauges to sink them, and that had them way off. Hearing the click as they closed and finger on the slide fixed it. This other bloke had a set of brass feeler gauges, no idea where he got them from but helpful with the non-magnetic effect between the magnet and the feelers and we spent a day doing multiple gap changes and seeing the effect. It did change where the spark timing happened but not a huge amount, maybe 10 to 15 degrees change and zero effect on my real issue. Bloody tedious draining oil to do the changes on a very hot engine over and over. Pantahs are such a fun bike when they are running right, very addictive with so much grip from there front ends. Or at least mine does with its 38mm fork.
 
Piet was right, if anything was even worse, worth a try I guess, great once above 4000 ish revs, bit of a dog below, guess will have to check pickup clearance, messy jobs on Pantahs and if I can't improve the running, will have to consider an after market ignition system, as it's almost unusable like this.
 
Yep. I'd strongly endorse the aftermarket ignition idea. You'll probably find that it'll transform the bike.

My Ducati MHR was always a bit of a dog to ride. Was OK beyond about 4000 RPM, but was difficult to start and I could never get it to idle well. It was also a bit rough on the transition from idle to higher revs. One of the Bosch units eventually died completely, so I replaced them with an aftermarket ignition (I used Ignitech but pretty much any modern ignition will be OK). It was like a different bike - started easily and settled to a nice regular idle when warm. I instantly regretted waiting until the Bosch unit died. If I'd known that those Bosch ignition units were the cause of its bad manners, I'd have got rid of them way earlier.

Incidentally, that was my very first Ignitech installation in about 2004 and it's still going strong. Blimey, those 20 years have flown by! It's obviously a pre-2004 version of their ignition. I don't remember what version number, but it was before the software had a graphical representation of the advance curve. It was just a table of numbers. While doing some research online, I found Ignitech's website and quite liked the specifications, and it was very cheap compared to other products. I asked around my contacts in the motorcycling universe, but nobody I knew had heard of Ignitech at that time. I figured for the price it was worth a punt - what could possibly go wrong? I'm glad I took the gamble because I was impressed with the ignition. I reckon I've done about Ignitech 20 installations since then on a whole range of different bikes. That's not a lot compared to guys who work on bikes full-time, but I'm just a home tinkerer who occasionally works on bikes belonging to mates.
 
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