What did you do to or for or with your Laverda today?

Agree with you John, it is not just the spark plug causing the problem. Back then SF2 and 3 came to Australia jetted very lean, 40 pilots that had them really hard to get a good idle, and 140 mains that were too lean, at least for full throttle on that long hill heavily loaded. Not many bikes were subjected to that back then, although SF generally have been known to like holed pistons, (which is not as horrific as the triples taste for busted rods). Subsequent swap to 45 and 145 and it was fine, living in Darwin with no open road speed limit, lots of flat out riding without a problem. I did a race meeting a few years ago and took advice from a top tuner here who said to use the hottest plug you can get away with, so swapped the 9s for 8s and had no problem at all, as the bike was jetted and everything else set up correctly. Next meeting I got the heebie jeebies and went back to the colder plugs though.
Those Bosch GT40 coils had a bad reputation back in the day, fortunately there was rarely a need to replace the original coils from the factory.
There was much discussion previously here about plug chops being useless indicators with modern/lead free fuels. Is that still the case?
 
Last weekend, I rode across Sydney to the rego BBQ without wearing custom-made earplugs. It's been many years since I hadn't worn ear protection, and I wanted to see the effect. The first thing I noticed was a loud churping noise on every bump, which concerned me greatly. That sound was my left muffler wobbling back a forth, approximately 15mm. I knew it was moving a bit, but I didnt expect all the sound being generated. It needs a good looking at as both ends are tightly attached, the muffler front end with thick solid Conti style Ducati stainless hoseclamps 30mm long and 2mm thick, great quality and standard, pretty new double rubber muffler mounts attached with stainless niloc nuts. The point I am making is it's good to ride occasionally without earplugs to notice new sounds, including PINGING, that go unnoticed so easily. The other muffler is attached the same way, and it's solid except for its correct flex on the rubber mounts. The only difference is a slight cutout on the muffler mount plate to clear the 3c rear brake light switch on the loose side. Maybe that plate has work-hardened and cracked?
 
MarnixSFC said:
One thing is for certain, running B8s on a small valve S or SF is NOT a good idea.

Marnix
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That used to be true.
I run 8s in my S, I used to run 9s, but now they foul. I've put about 10 000 km on the S like that.
I've also gone down from 55 pilots to 47 otherwise the bike is too rich. 45 would be better but I'm holding back.
Likely that opening out the inlet ports from 27mm to 30 is also to be taken into account.
Paul
 
Must be different fuel you get over there, Paul. I've run 9s or equivalent since i got my SF1 in early 1975 and am yet to foul a plug. Have built numerous motors and always specified 9s - never had a customer complain of fouled plugs. You have to take into account how hard you push your motor as well. My bikes will consistently see high revs and on the open road they'll see high speed.
 
lavgert said:
Hi Marnix, what spark plug would you recommend for a small valve S or SF?
Ciao, Gert
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B9ES or similar. No fancy versions like Iridium, just the basic thing.
I use them in all my 750s, except the Elettronica (B8ES).

In my early Laverda days (mid 70ies), everybody raved about the Lodge racing plugs as being best. In that vein I started to use B10E which worked well in the days when I used to ride to the south of France with 160 cruising speed with two up, Krauser cases, tents and a tank bag that I could barely look over. All worked well until we reached our destination where we only did the ride of a few km from tent to beach and vice versa on unpaved road through the vineyards. That’s when they started to foul big time..

Using B9ES in my Egli with small valve engine on the racetrack, and on my just finished 750S project, which has a small valve engine too, yet with an SF2 crankshaft. Did a few upgrades in the rolling chassis depertment.. 😉 Boy do I love the result!

Marnix
 

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Vince said:
Last weekend, I rode across Sydney to the rego BBQ without wearing custom-made earplugs. It's been many years since I hadn't worn ear protection, and I wanted to see the effect. The first thing I noticed was a loud churping noise on every bump, which concerned me greatly. That sound was my left muffler wobbling back a forth, approximately 15mm. I knew it was moving a bit, but I didnt expect all the sound being generated. It needs a good looking at as both ends are tightly attached, the muffler front end with thick solid Conti style Ducati stainless hoseclamps 30mm long and 2mm thick, great quality and standard, pretty new double rubber muffler mounts attached with stainless niloc nuts. The point I am making is it's good to ride occasionally without earplugs to notice new sounds, including PINGING, that go unnoticed so easily. The other muffler is attached the same way, and it's solid except for its correct flex on the rubber mounts. The only difference is a slight cutout on the muffler mount plate to clear the 3c rear brake light switch on the loose side. Maybe that plate has work-hardened and cracked?
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I often forget to put earplugs in and sometimes if I am not going far I don’t stop - but without my 2022 Triumph triple really does sound like a bag of nails -but the 120 engine in the Corsa sounds much sweeter than my 180 and the Formula is the same as the 180 for mechanical aptitude 😳
 
piranha-bro2 said:
Must be different fuel you get over there, Paul. I've run 9s or equivalent since i got my SF1 in early 1975 and am yet to foul a plug. Have built numerous motors and always specified 9s - never had a customer complain of fouled plugs. You have to take into account how hard you push your motor as well. My bikes will consistently see high revs and on the open road they'll see high speed.
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I can only surmise that amongst other factors, fuel has to do with it.
On all my 750s, if I hadn't leaned the pilot jets, the plugs would be dead after the third start from cold if not the second. And they'd foul the plugs, and that includes the SFC which would need the plugs changing after less than 10 km of leisurely use to warm it up or after the second or third start from cold. I've gone down five points on the pilots and it's become civilised again which it always was years ago, but now on NGK 8s rather than 9s.
Friends with British bikes have noticed the same phenomenon.
Paul
 
In between trying to watch a bit of racing and complete the groundwork for moving the summer house to make way for a bigger shed, I’ve also been spending a bit of time in the workshop, with my able assistant, Martin M completing a bit of post testing/parading maintenance.
 

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The Sock said:
That is a beautiful 750, Marnix! Love the colour!
Pretty much my ideal spec, 'S' tank, slash cut exhausts, twin disc on 38mm Cerianis. The only thing I'd change would be to polish the fork sliders.
If you ever think of selling,...
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Thanks. A lot of thought went into that front end. I had a choice between two 38mm forks, one polished and one black, and the original 35mm drum forks, all NOS. Also have a selection of Grimeca and Laverda drum brakes, as well as Ceriani and Fontana drums. The latter two would look mighty cool, but as race drums they can bite when cold, plus they have no speedo drives which is impractical, but after considering everything, deep down I really wanted, and chose, the trusted Brembo brakes.
The black sliders are a touch of old S, I think they look right with the black frame. I also considered mounting the old Bosch headlight and Smiths clocks, but that to me just did not look right, so in the end I decided for the SF2 headlight and ND clocks, and they look lovely in combination with the line of the rest of the bike. More importantly, I did choose a pair of 750SFC triple clamps which run parallel to the headstock, just like the S had. It makes handling pleasantly light.

Built up the engine entirely from spare parts, with a NOS SF2 crankshaft as a basis, the rest is all S spec. These engines were quick but prone to detonation and this one is no exception, despite the use of B9s and so I’m happy to have the DMC to alter the advance angle and curve.

Heaven sent!

Marnix
 

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It's a beautiful combo of bits, Marnix. What's the 4S cam like? Looking at cam timing figures, the 4S isn't far off a 5C. My SF1 (13768) supposedly had a 5/1 but mine was unmarked and I always wondered if it might have been a 4S - it was very willing at high revs. I have another cam in my box of bits that looks very much like a 5C but that is also unmarked ... it's entirely possible it was the actual cam that came out of my motor when I went to 5C cam and valves.

One of the reasons I ask is that being close to 5C timing I was curious about how it works with the twin mufflers, where a 5C just doesn't like std mufflers. I fitted std SF headers and Contis to get a roadworthy and the motor was choked - it was gutless. Maybe the slightly more conservative timing of the 4S over a 5C enables the motor to breathe with mufflers and negates the choking?
 
piranha-bro2 said:
It's a beautiful combo of bits, Marnix. What's the 4S cam like? Looking at cam timing figures, the 4S isn't far off a 5C. My SF1 (13768) supposedly had a 5/1 but mine was unmarked and I always wondered if it might have been a 4S - it was very willing at high revs. I have another cam in my box of bits that looks very much like a 5C but that is also unmarked ... it's entirely possible it was the actual cam that came out of my motor when I went to 5C cam and valves.

One of the reasons I ask is that being close to 5C timing I was curious about how it works with the twin mufflers, where a 5C just doesn't like std mufflers. I fitted std SF headers and Contis to get a roadworthy and the motor was choked - it was gutless. Maybe the slightly more conservative timing of the 4S over a 5C enables the motor to breathe with mufflers and negates the choking?
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What's the difference in lift between a 4S and a 5C?
5C was intended for a machine with 7mm valve stems. No doubt makes a huge difference in the way the engine goes.
In no way does my S ressemble my SFC with a 5C. Even if the 5C is very forgiving at low and medium revs on the SFC, my S has a load more stomp low down.
Paul
 
Paul Marx said:
What's the difference in lift between a 4S and a 5C?
5C was intended for a machine with 7mm valve stems. No doubt makes a huge difference in the way the engine goes.
In no way does my S ressemble my SFC with a 5C. Even if the 5C is very forgiving at low and medium revs on the SFC, my S has a load more stomp low down.
Paul
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Not sure about lift - good point. But the small valves, inlet ports and carbs on the S will definitely account for the low end grunt.

I think the main advantage of the 7mm SFC stems is lower weight, not horsepower (although there would be a slight advantage in flow from a narrower stem in the port) - they are identical size at the head to big valve 8mm SF..
 
piranha-bro2 said:
Not sure about lift - good point. But the small valves, inlet ports and carbs on the S will definitely account for the low end grunt.

I think the main advantage of the 7mm SFC stems is lower weight, not horsepower (although there would be a slight advantage in flow from a narrower stem in the port) - they are identical size at the head to big valve 8mm SF..
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Revs.
The stomp of the S is also down to the 5 or 7 kg more on the crank than the SFC.
Paul
 
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