Newby needing advice

[Laverdalothar]

See and judge yourself if it was an overhaul or a restoration... (oh - and I was wrong, it has been more than 15 years ever since...)

"How it all began" or "Can you be re-infected again and again?

well - there are two... one is a surely either a gearbox thing (a high "wiiiiiiiii" that changes with revs; sounds like a bearing...) and the other is a ratteling sound from the front. Maybe the cam-chain or a valve... :-\ Also since some 200 Kilometers, the seal between cylinders and...

laverdaforum.com

 

[Alan]

See and judge yourself if it was an overhaul or a restoration... (oh - and I was wrong, it has been more than 15 years ever since...)

"How it all began" or "Can you be re-infected again and again?

well - there are two... one is a surely either a gearbox thing (a high "wiiiiiiiii" that changes with revs; sounds like a bearing...) and the other is a ratteling sound from the front. Maybe the cam-chain or a valve... :-\ Also since some 200 Kilometers, the seal between cylinders and...

laverdaforum.com

Just read through the thread again Lothar, you've had a remarkable time with your bikes over the years. You mentioned in one of the photos showing the 750 head that a mod had been done to improve oil flow to the cams. I'd be interested to hear more of what the mod is for future reference.

Al

 

[piranha-bro2]

Just read through the thread again Lothar, you've had a remarkable time with your bikes over the years. You mentioned in one of the photos showing the 750 head that a mod had been done to improve oil flow to the cams. I'd be interested to hear more of what the mod is for future reference.

Al

Might be the mod the factory made with the SF3 - drilling two small holes from the central channel (that carries oil from front to rear studs/rocker spindles). The holes are angled to spray oil (sort of) directly onto the top of the cams. IMHO a mod best done in conjunction with the fitment of a 10mm SFC oil pump (std SF is 6mm). I drilled the holes in my SF1 head thinking it must be a good thing, but later blocked them up, as with a 6mm pump, I preferred all the oil going through the spindles to under the rockers and cam. I only drilled the holes again after fitting a 12mm oil pump.

If everything is clear of blockages, the cams get plenty of oil with a stock 6mm pump. The key is to ensure the middle four studs front and rear can't block the entrance to those central channels in the top inner face of the head. All it requires are thin L-shaped pieces of wire to make it impossible for the studs to block any oil. Some top covers even need to have the middle four holes ovalised slightly to allow the thin wire to fit, which probably means the holes were actually pulling the studs in and causing that very blockage.

 

[JimmyO]

Attached is pic of front hub/brake. Frame /engine numbers match, on basis of replies bike seems to be 72/73 model so SF1. Looks straight and unmolested, it hasn't been used much in recent years. Main issue seems to be the crazed paint at the tank. $64,000 question is price- quoted at £7k so roughly €8500.

 

[Paul Marx]

Attached is pic of front hub/brake. Frame /engine numbers match, on basis of replies bike seems to be 72/73 model so SF1. Looks straight and unmolested, it hasn't been used much in recent years. Main issue seems to be the crazed paint at the tank. $64,000 question is price- quoted at £7k so roughly €8500.

It does look like an SF1.
Price is way too high. Make sure that there's no putty under that craze paint.
Paul

 

[Laverdalothar]

Just read through the thread again Lothar, you've had a remarkable time with your bikes over the years. You mentioned in one of the photos showing the 750 head that a mod had been done to improve oil flow to the cams. I'd be interested to hear more of what the mod is for future reference.

Al

Might be the mod the factory made with the SF3 - drilling two small holes from the central channel (that carries oil from front to rear studs/rocker spindles). The holes are angled to spray oil (sort of) directly onto the top of the cams. IMHO a mod best done in conjunction with the fitment of a 10mm SFC oil pump (std SF is 6mm).

Exactly the modification OCT did to the head, including the larger Oil-Pump Engine was running very smooth. Many 750 move backwards when you have them on the center stand and open throttle. Have even seen one that turned in a circle... mine was standing completely still. Great job Piet has performed while at OCT, worth every cent I spent!

 

[piranha-bro2]

Piet knows his shit when it comes to balancing - he just gets it right. I've ridden a crazy variety of ex-factory SFs with vastly differnt vibe characteristics - makes me think the balancing work was a bit hit-and-miss.

 

[Paul Marx]

Piet knows his shit when it comes to balancing - he just gets it right. I've ridden a crazy variety of ex-factory SFs with vastly differnt vibe characteristics - makes me think the balancing work was a bit hit-and-miss.

Laverda cranks ex factory are phased from 356 to 364 ° which is what the splines on the centre piece allow.
My S crank was at 357° before Phil Todd rebuilt it a long time ago.
That and 27mm inlet ports for the 30mm carbs.
All hand built.
Paul

 

[Alan]

Might be the mod the factory made with the SF3 - drilling two small holes from the central channel (that carries oil from front to rear studs/rocker spindles). The holes are angled to spray oil (sort of) directly onto the top of the cams. IMHO a mod best done in conjunction with the fitment of a 10mm SFC oil pump (std SF is 6mm). I drilled the holes in my SF1 head thinking it must be a good thing, but later blocked them up, as with a 6mm pump, I preferred all the oil going through the spindles to under the rockers and cam. I only drilled the holes again after fitting a 12mm oil pump.

If everything is clear of blockages, the cams get plenty of oil with a stock 6mm pump. The key is to ensure the middle four studs front and rear can't block the entrance to those central channels in the top inner face of the head. All it requires are thin L-shaped pieces of wire to make it impossible for the studs to block any oil. Some top covers even need to have the middle four holes ovalised slightly to allow the thin wire to fit, which probably means the holes were actually pulling the studs in and causing that very blockage.

Thanks for the detailed reply. All food for thought as usual.

Al

 

[sfcpiet]

Although it is possible for 750 cranks to have been manufactured out of phase, it is pretty rare, likely far less than 0.5%. Mostly a lot less than Pauls' quoted range too. The crank webs are not dependant on the splines of the centrepiece, new webs don't have any! More a case of a web shifting slightly before final pressing. Unfortunately, not much can be done, except perhaps finding a centrepiece with better-matching splines. The splines were machined randomly, so each centre pair of webs and their journal turn out unique and must be considered as a pair/set and cannot be randomly mixed with bits from other cranks.

On a whole, factory balancing was quite OK. Most vibes result from worn-out or crooked cranks, or far-too-heavy/light pistons. After an overhaul, even the harshest vibrators mostly come out quite smooth and docile.

Camshafts seem to be a whole different story though, I've found them up to 13° out! Perhaps some rogue batches found their way into the spares supplies, cams were not always replaced as pairs.

piet

 

[Paul Marx]

Although it is possible for 750 cranks to have been manufactured out of phase, it is pretty rare, likely far less than 0.5%. Mostly a lot less than Pauls' quoted range too. The crank webs are not dependant on the splines of the centrepiece, new webs don't have any! More a case of a web shifting slightly before final pressing. Unfortunately, not much can be done, except perhaps finding a centrepiece with better-matching splines. The splines were machined randomly, so each centre pair of webs and their journal turn out unique and must be considered as a pair/set and cannot be randomly mixed with bits from other cranks.

On a whole, factory balancing was quite OK. Most vibes result from worn-out or crooked cranks, or far-too-heavy/light pistons. After an overhaul, even the harshest vibrators mostly come out quite smooth and docile.

Camshafts seem to be a whole different story though, I've found them up to 13° out! Perhaps some rogue batches found their way into the spares supplies, cams were not always replaced as pairs.

piet

Not doing cranks myself, I can only repeat what Phil told me years ago. And he did tell me that my S crank was at 357°. Level of vibration was notably less after rebuild.
Concerning rogue parts, as you know, the remaining stocks of the factory after closure were raided by dealers who sold on the parts, including parts that had been put aside.
Paul
Now I have a 20 ton press, maybe I should press a 750 crank apart.

 

[sfcpiet]

Not doing cranks myself, I can only repeat what Phil told me years ago. And he did tell me that my S crank was at 357°. Level of vibration was notably less after rebuild.
Concerning rogue parts, as you know, the remaining stocks of the factory after closure were raided by dealers who sold on the parts, including parts that had been put aside.
Paul
Now I have a 20 ton press, maybe I should press a 750 crank apart.

Maybe you shouldn't...

piet