750 sf ignition problem

Just to update everyone.
I've fitted a another duel outlet coil, TEC MP08 off of a VFR, fitted new HT leads and new non resistor spark plugs, (NGK plug caps), and it is again sparking and running on both cylinders.
Haven't tried it out on the road yet as we are having a wet spell, seemingly especially when I'm not at work, but generally if it ticks over it should be ok.
 
Lyndoneil said:
Just to update everyone.
I've fitted a another duel outlet coil, TEC MP08 off of a VFR, fitted new HT leads and new non resistor spark plugs, (NGK plug caps), and it is again sparking and running on both cylinders.
Haven't tried it out on the road yet as we are having a wet spell, seemingly especially when I'm not at work, but generally if it ticks over it should be ok.
Click to expand...
Do you have resister spark plugs or leads? My understanding is that having no resister at all can cause interference to all sorts of stuff, but shouldn't double up on it (e.g. resister plugs and caps).
Good to hear that you got it sorted in time for the summer.
 
electricity is weird shit! (as are a lot of the sciences (think quantum mechanics / super-fluids / evolution etc. etc.)) and even just a basic setup like an ignition can befuddle most. Opinion only, but I'm guessing that the answer (resistive leads or plugs) is somewhat of a 'balance'.

The interference thing is to avoid stray currents being generated in nearby systems. It's likely that the guy in the car next to you can hear the buzz of your ignition through his radio (old school) but it can also interfere with your own black box (if that's your setup).

Then there is the concept of resistance 'compressing' the spark to be a shorter duation and hotter. Maybe? But I've successfully run a few cars and bikes on copper or stainless leads with no problem. I've even read that the plug gap should ideally be larger than the average 30 thou., and even a lawn mower will jump a few inches (weakly, but enough to ignite fuel). At the end of the day, it's a balance, before even getting into coil impedance etc..

For anyone who has read this so far .... I have absolutely no idea of what I'm talking about or what's right / wrong! But I prefer R on the plug(s).
 
Lyndoneil said:
Just to update everyone.
I've fitted a another duel outlet coil, TEC MP08 off of a VFR, fitted new HT leads and new non resistor spark plugs, (NGK plug caps), and it is again sparking and running on both cylinders.
Haven't tried it out on the road yet as we are having a wet spell, seemingly especially when I'm not at work, but generally if it ticks over it should be ok.
Click to expand...
I expected that you would narrow it down to the coil. The old wives' tales about points being the better option hold no water with me. Boyer ignitions are bulletproof IMHO and will provide decades of trouble free service.

Good to hear you're back up and running
Gerald
 
Just to update further, tried it on a ride, still same problem, left cylinder miss firing and sooting up the plug so will have to start measuring resistance on components, have been in touch with Boyer to ask what the optimum coil set up is with these ignition, but haven't had a reply yet.
Information on the internet is contradictory, if single coils are used it seems they have to be wired inline, which is pretty much the same as a dual outlet coil.
I've 2 PVL 6 volts coils that I have never used, brought for another project, some seem to indicate that these give a better spark, but it's behind my understanding as to whether they are compatible.
 
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Doubt that the dual outlet TEK coil is the problem. You'd be very unlucky to have swapped the duff original coil for a duff replacement.
I'd be looking at stuff you haven't changed. Wiring and their connectors... and the trigger (or pick up) that is firing the LH cylinder.

Advocates of the PVL coil believe that they are quicker to saturate and so provide the maximum spark voltage especially at higher revs. I've not seen any definitive data to support the claim. I run twin output TEK coils on my 6 plug triple which runs cleanly to 9000 rpm on the dyno. There's a YouTube video of that...
 
Both of my 750's run twin ND coil, IIRC a common coil used in various Jap bikes.
You should be able to source a cheap second hand coil.

Gerald
 
1200 JOTA said:
I've successfully run a few cars and bikes on copper or stainless leads with no problem.
Click to expand...
Stainless spark plug leads don't have a stainless conductor. It's just a braided stainless steel outer sleeve, like those used on braided brake lines. Its purpose is mainly to protect the wire against mechanical damage and perhaps provide some RF shielding. The conducting core of the lead is still copper or carbon.

Stainless steel is a lousy conductor of electricity with about 40 times the resistivity of copper and 10 times the resistivity of ordinary steel. If you're using stainless to carry electricity (for example, an earth return via stainless indicator indicator stalks) it'll be OK as long as the cross sectional area is large, but stainless wire is more like a heater element than a conductor.
 
Lyndoneil said:
Just to update further, tried it on a ride, still same problem, left cylinder miss firing and sooting up the plug so will have to start measuring resistance on components, have been in touch with Boyer to ask what the optimum coil set up is with these ignition, but haven't had a reply yet.
Information on the internet is contradictory, if single coils are used it seems the have to be wired inline, which is pretty much the same as a dual outlet coil.
I've 2 PVL 6 volts coils that I have never used, brought for another project, some seem to indicate that these give a better spark, but it's behind my understanding as to wether they are compatible.
Click to expand...

A dual output coil is not the same as 2 6V coils in series.

A dual coil only has one secondary (high voltage) circuit and the spark plugs are wired in series.
With 2 x 6V coils, the primary circuits are wired in series, but they have two (independent) secondary HV circuits (one to each spark plug) that are wired in parallel.

When the spark plugs are wired in series as with your dual coil, the same 'sparking' current is passing through both plugs*. So if one spark plug is fouling and the other isn't, the problem is very unlikely to be with the coil.

You could have a dodgy plug (that's passing current but not sparking properly - could be a cracked ceramic insulator for example), or there's some mechanical issue with that cylinder, such as bad fuel mixture, poor compression, or oil getting into the mixture.

Here's the diagnostic test to work out what's going on:

Clean the spark plugs (burn the shit off the fouled plug with a propane torch) and swap them into the opposite cylinders.

If the fouling problem follows the plug to the opposite cylinder, you can be 100% sure that have a dodgy spark plug.

If the same cylinder fouls up again while the other cylinder continues to run OK, then there's some kind of problem with that side of the bike. There's a possibility that you could have a faulty spark plug lead or cap that's allowing the sparking current to track down the outside of the plug, or jump to some nearby earth - remember that the current must be going somewhere to allow the other plug to fire. However, I reckon it's more likely that you have a fuelling or mechanical problem with that cylinder and it's nothing to do with the ignition system.

* Yes, I know the polarity of the plugs is different, but that shouldn't cause the problem that Lyndoneil is experiencing.
 
Make sure the choke mechanism on the carb is going off fully. If the cable is sticking or short it will run rich on that cylinder.
 
Lyndoneil said:
Just to update further, tried it on a ride, still same problem, left cylinder miss firing and sooting up the plug so will have to start measuring resistance on components, have been in touch with Boyer to ask what the optimum coil set up is with these ignition, but haven't had a reply yet.
Information on the internet is contradictory, if single coils are used it seems they have to be wired inline, which is pretty much the same as a dual outlet coil.
I've 2 PVL 6 volts coils that I have never used, brought for another project, some seem to indicate that these give a better spark, but it's behind my understanding as to whether they are compatible.
Click to expand...
I feel your pain. I have the same problem except non-fire on the right side. Replaced coil, plug wires and plug... no difference. I bought 2 new condensers thinking one might be bad. Went to replace them and guess what, they are riveted in place along with the cam wiper.
I will have to remove everything, take it to work, grind off the rivets and probably braze up the oversize holes, re-drill and then tap the holes. Then screw in the new condensers. Even then it's a crap shoot that it works and fixes my problem. I had to wait over a month to get the parts so you can say I am a bit frustrated.
If all works well, it might.....might work but I have my doubts. This bike ran fine when I bought it years ago and when I trucked it home, it never ran on two cylinders again. Luckily I own a couples of BMW's. Most reliable motorcycle on earth! The Laverda isn't a bike I would take more than walking distance from home. Just like a hot woman, nice to look at but she'll take your money and stab you in the back.
I wish I could find somebody to work on it, or to buy it. I hate the thing.
 
Blackwolf said:
I feel your pain. I have the same problem except non-fire on the right side. Replaced coil, plug wires and plug... no difference. I bought 2 new condensers thinking one might be bad. Went to replace them and guess what, they are riveted in place along with the cam wiper.
I will have to remove everything, take it to work, grind off the rivets and probably braze up the oversize holes, re-drill and then tap the holes. Then screw in the new condensers. Even then it's a crap shoot that it works and fixes my problem. I had to wait over a month to get the parts so you can say I am a bit frustrated.
If all works well, it might.....might work but I have my doubts. This bike ran fine when I bought it years ago and when I trucked it home, it never ran on two cylinders again. Luckily I own a couples of BMW's. Most reliable motorcycle on earth! The Laverda isn't a bike I would take more than walking distance from home. Just like a hot woman, nice to look at but she'll take your money and stab you in the back.
I wish I could find somebody to work on it, or to buy it. I hate the thing.
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Not sure why replacing the condensors needs to be such a big job!!
You don't have to "remove everything". Just take the points plate off and carefully drill the old rivets, they will come out easily and bolt on your news ones using appropriate size nut and bolt - 10 min job (cut to length if necessary). Put plate back on and adjust the gaps and timing.
Hard to comment on your other problem, you have an old motorcycle with simple ignition system so just a matter of going through the basics........Much like you would do with an old BMW! (although if the condition of your wiring and connectors is unknow, finding broken wires or dodgy earths can be frustrating - like any brand often depends on who has worked on the bike before)
 
All my 750s going back 47 years and 100s of thousands miles never had ign problems. Never not got me to wherever I was going either. Just saying they're pretty bullit proof and as reliable as any BM, but way more exciting to ride. The ign is very simple with points so shouldn't be an issue sorting it. Follow Peter's direction replacing the condensers and go from there.
As for not taking it more than walking distance from home,
You are missing out on a fantastic ride. I love my BM but it's used for off road and back tracks. For tarmac the laverda is first choice.
 
Shajota said:
Not sure why replacing the condensors needs to be such a big job!!
You don't have to "remove everything". Just take the points plate off and carefully drill the old rivets, they will come out easily and bolt on your news ones using appropriate size nut and bolt - 10 min job (cut to length if necessary). Put plate back on and adjust the gaps and timing.
Hard to comment on your other problem, you have an old motorcycle with simple ignition system so just a matter of going through the basics........Much like you would do with an old BMW! (although if the condition of your wiring and connectors is unknow, finding broken wires or dodgy earths can be frustrating - like any brand often depends on who has worked on the bike before)
Click to expand...

I’m feeling a points/electronic argument about to erupt..... enter Paul.
 
In 7000 km since the sf2 hit the road again, i have had 1 failed coil, 1 failed condenser, 1 failed voltage regulator. All good now, nice little run up the old rd and back this morning, bella machina😍
 
A good argument against points ignition. If you'd installed electronic ignition, those ignition failures probably wouldn't have happened.
An electronic box doesn't use condensers and the electronically controlled dwell gives the coils an easier life and allows them to run cooler.
 
martymoose said:
In 7000 km since the sf2 hit the road again, i have had 1 failed coil, 1 failed condenser, 1 failed voltage regulator. All good now, nice little run up the old rd and back this morning, bella machina😍
Click to expand...
I was up at The Pits yesterday in the car and noticed something, not pleasant. Lots of Agresive screaming, I asked what it was about and was told some idiot doing laps had come into the car park to do a ride through at speed and crashed into another bike. He wanted to leave before the cops arrived and the screaming was him being told to not leave the scene of the accident.
This car park is narrow and tight and crowded. Stupid dangerous thing to do. It was getting heated when I was leaving.
 
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