750 sf ignition problem

[Paul Marx]

Well Paul, To give you a quick summary of my issue with the ignition, I have an engine that starts, runs but the right exhaust is stone cold....No spark. Replaced the coil, plug wire and spark plug and still no spark and a cold pipe. I am assuming it's a condenser because I had one fail on a car of mine back in the 70's and the condenser failed when the car drove thru a dip in the road and the shock killed the condenser. The bike ran fine when I bought it and while driving home with it in the back of my truck, it must have jarred it enough to kill the condenser (I assume). So here I am and I have to put the new ones in but I need to grind off the rivets that secure them but that's an issue for tomorrow when I can take it to work where I have the facilities to do the job properly.
I am totally open to remote mounting the condensers but I have no idea on where to locate them or for that matter, how to even wire them up. I know they only have one wire but where do I connect the wire? Should I mount the condensers to an aluminum plate and go from there. I want them located in such a place I can replace them in a minute or so, assuming they are the Achilles heal to this engine. Does it matter how long the wires are and how far they are from the points? You may know by now I have no clue on the workings of an ignition system except that when it works, all is good.

You're not going about it properly.
I've been running my SF2 with the same condensers since 1992 and it's very likely that they were fitted by the factory in 1973.
Condensers do break down but they are not the Achilles heel of this engine which doesn't really have any.

That jolt could have done all sorts of things notably broken a wire or undone a loose connection.
You need to check, with a voltmeter or a 12 volt bulb, positive feed to the coils, positive feed to the points and the condenser from the coils, it's a common feed.
Are the plug caps receiving volts. You can swap plug leads from side to side and see if your problem changes sides or not.

It's a very simple system plus from coil to condenser and points. Static point and condenser are both earthed, condenser via it's body. The opening of the circuit when the points open causes the coil secondary winding to discharge via the plug which is earthed.

No doubt somebody better than me with electrics will come along and say that I'm talking balls. But that's it basically. Stay simple and test everything.
Forget your fixation on condensers.
And as has been mentioned, running an old mechanical contraption requires some basic skills. They all give problems at some time or other, even old BMWs.

Paul

 

[martymoose]

Yes you are... Won't run at all without condenser

 

[piranha-bro2]

I can understand your frustration, but unfortunately your lack of experience with very simple 12V electrics is clouding your judgement. As mentioned, a Laverda SF ignition system is nigh on bulletproof if its basic components are functioning (12V battery fully charged, twin condensers/points/coils/plug caps/plug leads/plugs). When I had points on my SF1 I covered 160,000km over a 5 year period through some of the most remote parts of Australia. I probably fitted new points once in all that time - never, not once, had to replace the condensers.

Your bike is old. OK, so fit new condensers as per the drill, screw and nut method outlined in this thread. But to achieve the result you want you need to know the absolute basics of the system - like where to attach the wires, so I'd suggest ...

Fit but do not connect the condensers. Take it to any auto elec with experience in points/condenser ignition systems. Have them attach the wires, adjust points gaps (.4mm - file and clean surfaces if nec), check the timing statically, trace the fault (if it still exists).

Absolutely no point blaming the bike for your lack of experience with its simple but robust makeup. But as mentioned, we do understand your frustration.

 

[Blackwolf]

I can understand your frustration, but unfortunately your lack of experience with very simple 12V electrics is clouding your judgement. As mentioned, a Laverda SF ignition system is nigh on bulletproof if its basic components are functioning (12V battery fully charged, twin condensers/points/coils/plug caps/plug leads/plugs). When I had points on my SF1 I covered 160,000km over a 5 year period through some of the most remote parts of Australia. I probably fitted new points once in all that time - never, not once, had to replace the condensers.

Your bike is old. OK, so fit new condensers as per the drill, screw and nut method outlined in this thread. But to achieve the result you want you need to know the absolute basics of the system - like where to attach the wires, so I'd suggest ...

Fit but do not connect the condensers. Take it to any auto elec with experience in points/condenser ignition systems. Have them attach the wires, adjust points gaps (.4mm - file and clean surfaces if nec), check the timing statically, trace the fault (if it still exists).

Absolutely no point blaming the bike for your lack of experience with its simple but robust makeup. But as mentioned, we do understand your frustration.

What is so frustrating is that it was working perfectly when it was loaded into the truck. I rode it up the ramps and secured it myself. It was not touched or left my sight until I arrived home. When I got home some 6 1/2 hours later, I released the straps and rolled it down the ramp. I fired it up and it seemed to run but was under powered. I knew something wasn't right. No hot exhaust from the right side. It has never fired on that right side. I can see if there was some damage or it fell over but nothing like that happened. It was working, and shut off. Then 6 1/2 hours later it wasn't. Simple as that. Why just one cylinder not firing?
If it doesn't work, I will try to find someone near me that can troubleshoot it and repair it. If I have to drive it 400 miles to get it done, I will. All it take is money.

 

[Vince]

Its been a while since I read this thread, are you sure you just haven't failed a plug. Running too long with the choke can do this easily. Have you tried new plugs

 

[Blackwolf]

Its been a while since I read this thread, are you sure you just haven't failed a plug. Running too long with the choke can do this easily. Have you tried new plugs

Yes, new plugs.

 

[chrisk]

What is so frustrating is that it was working perfectly when it was loaded into the truck. I rode it up the ramps and secured it myself. It was not touched or left my sight until I arrived home.

Put it back on your truck, take it to an auto elec, have a beer while they sort it, ruminating over something that happened 40 years ago isn’t helping.

Okay, seems the truck is the culprit ...... joke Joyce.

Put it back on your truck, take it to an auto elec, have a beer while they sort it, then ride it home. Don't tell the truck what you are up to?

All sound advise by the others here (and even a special response from Q the LF hermit), she'll be right.

 

[Blackwolf]

Okay, seems the truck is the culprit ...... joke Joyce.

Put it back on your truck, take it to an auto elec, have a beer while they sort it, then ride it home. Don't tell the truck what you are up to?

All sound advise by the others here (and even a special response from Q the LF hermit), she'll be right.

I think the bike was jealous of the truck for my attention. But I will have a cold one just to make sure. Can't be too careful.

 

[bazzee]

How do you go about re-locating the condensers? Do you just attach the wire to the coil? That seems way to easy. There must be more to it than that. I am all for simplicity and reliability.

not sure if condensors are essential (?) ... don't they just save the points from arcing? (should still run?)

p.s. I may be totally wrong!

If you're unfamiliar with electrics then likely best to stick with what you've got. Should be fine, I was just offering an opinion...
And yes, the condenser is necessary. that's why all points and coil ignitions have them. (Well there may be exceptions e.g. energy transfer magnetos?)

cheers,
bazzee

 

[chrisk]

Your wiring is 40+ years old, it gets brittle and breaks. Could be just a bad/broken connection somewhere.
The hardware may well be working fine, if it's fed the right smoke.

 

[Paul Marx]

Blackwolf,
Are you sure it's an electrical problem?
Once again, you haven't mentioned the basics unless I'm much mistaken?
You have a cold side to your engine, but is it sparking that side?
Is it getting petrol? A bike that has been restarted without a thorough cleaning of the carbs is going to suck up a load of crud into the jets. If the carbs were cleaned but badly rebuilt, that jolt could have dislodged a jet or a needle. The possibilities are endless.

Be systematic in your trouble shooting.
Spark?
Petrol?

And work on from there.

Paul

 

[Blackwolf]

Brand new needle and seats, new fuel lines, filters. I know for a fact I have fuel! I did get in contact with an Italian bike restoration shop. I will try to get it down to him over the Christmas holiday. Things are looking up.

 

[Paul Marx]

Brand new needle and seats, new fuel lines, filters. I know for a fact I have fuel! I did get in contact with an Italian bike restoration shop. I will try to get it down to him over the Christmas holiday. Things are looking up.

Good, keep us posted. Your problem is certainly simple but they can be hard to find.
After a while, you'll learn to keep away from bike restoration shops.

 

[Blackwolf]

I will have to invest in some diagnostic tools. Part of the issue is I also have limited space to work on vehicles.

 

[Shajota]

Brand new needle and seats, new fuel lines, filters. I know for a fact I have fuel! I did get in contact with an Italian bike restoration shop. I will try to get it down to him over the Christmas holiday. Things are looking up.

(Ok, promise this will be my last post on this subject, but I feel a sense of frustration at lack of 2 way info)
You say it was running fine until you took it home on a truck!! As already mentioned that points to something very simple however you haven't stated what checking has actually been done and have not replied to Pauls posts above where he suggests basic checks.
Before you spend money at a shop, have all the simple things mentioned been checked?? - Such as:-
(Sorry Paul, I know I am repeating what you have already said)
You say you definately have fuel - do you have spark?
Is your points gap correct? (Could be something as simple as one side not quite done up tight and closing up when jolted while on the truck)
Have you swapped plug leads over to try and narrow down where, if you are losing spark?
Is there power to both coils?
Have you checked wiring that one hasn't come loose somewhere and ensured earths are good etc etc?? (Obviously a broken connection may need narrowing down a bit)
If you have no room to work perhaps at least take the points cover off and turn it over with the starter motor and see if both points are firing regularly...........
Perhaps you have checked all of these things, however perhaps not as it's not obvious from posts................

 

[Blackwolf]

(Ok, promise this will be my last post on this subject, but I feel a sense of frustration at lack of 2 way info)
You say it was running fine until you took it home on a truck!! As already mentioned that points to something very simple however you haven't stated what checking has actually been done and have not replied to Pauls posts above where he suggests basic checks.
Before you spend money at a shop, have all the simple things mentioned been checked?? - Such as:-
(Sorry Paul, I know I am repeating what you have already said)
You say you definately have fuel - do you have spark?
Is your points gap correct? (Could be something as simple as one side not quite done up tight and closing up when jolted while on the truck)
Have you swapped plug leads over to try and narrow down where, if you are losing spark?
Is there power to both coils?
Have you checked wiring that one hasn't come loose somewhere and ensured earths are good etc etc?? (Obviously a broken connection may need narrowing down a bit)
If you have no room to work perhaps at least take the points cover off and turn it over with the starter motor and see if both points are firing regularly...........
Perhaps you have checked all of these things, however perhaps not as it's not obvious from posts................

I got the new condensers in and after struggling with getting the wires and those tiny nuts attached to the points it fires right up....on the left side . So it's off to the mechanic to deal with it. I have no way to diagnose an electrical problem. Electrical issues are best suited to those who know what to look for. I really don't want to spend a lot of money on it but it won't run if I don't. Nice to look at but it's spends more time just sitting there than being used.

 

[chrisk]

Laverda lesson #1. Turn those fuel taps off when sitting idle.
Hydraulic lock up is a common conversation here.

 

[Paul Marx]

You're not trying.
I'm an electrical virgin. All I know is that electricity must circulate between + and -.
You need a 12 V bulb or a tuppeny multimeter to check if juice is flowing.

Not expensive at all.

And wipe over your points with a non fluffy cloth imbibed with solvent. A dirty point will give the symptoms you have.

Paul

 

[Perry]

Still don't know if he's got a spark on the cold side. For some reason I feel I really need to know. Anyone live near by ?

 

[Blackwolf]

Laverda lesson #1. Turn those fuel taps off when sitting idle.
Hydraulic lock up is a common conversation here.

I did have fuel leakage thru the carburetors at one time. I pulled them off and cleaned them out. Bought new floats, needle and seats along with gaskets and fuel lines. I also put in a pair of inline filters. That problem is solved and fuel flow is as it should be.