rebuilt 750S 1970 start and first run

Laverda SF said:
Well we are still typing and editing - LOL
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I'm done correcting minor typos, you carry on editing.

Racial stereotyping goes against the grain for me but if you were Irish and insisting on digging your hole deeper I would carefully place a spade and a shovel against the wall and ask you to take your pick...
 
Put it this way the Suzuki xs400r is a dead goat found in wrecking yards  - Our 750's are still alive.

If you want the CDI Ignition take it as well as with minor mods it fits our Twins.

Mr "Laverda SF" is talking shit again?
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Onethinbloke = FO unless you have something worth contributing - BULLY - Not that I didn't like your story about the GL in your shop and glad to hear the GL will spin over 5500rpm. The 750S & SF are a Performance Breed Breganze capable of 7400+ rpm, I would advise you to help me rather then criticize me ;o)

If you don't belive my SF will hit 8000rpm with Stk Cast Pistons and 30A's with points, then  take a ride on her and we will discuss Canadian Vs European Motorcycle Ingenuity. Your the Bull Shitter in my opinion.

Are you and Cosi still fooling around in the ATTIC or what?
 
Laverda SF said:
Keith: What 750 Twin could rev like the Breganze 750 back then other then the Honda 750 4 - reaching 10G -
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How about a Moto Guzzi V7 Sport?
 
Yesterday I took the bike for a ride to meet up with my brothers and a bloke from England who is visiting. I kept the revs under 4000 but I could feel that she wanted to pull past that eagerly. So I cruised along happy as ever on a splendid summer morning, got to the rendevue point, my brothers garage, where the fellows where already waiting and proudly pulled up to show them my pride and joy. They looked at the bike and said: IT LEAKS GAS!!! And bloody hell, It was pissing out behind the righthand kneerubber on the tank. took the tank of and hosed the remaining gas over In my Guzzi S3 that was standing there. So the tank leak somewhere around the joint where it holds the kneerubbers.
Hope KREEM will fix it.

Anyway, we had a great day riding with two Guzzis, Darmah SS and BMW R75/5.

David
 
Are you and Cosi still fooling around in the ATTIC or what?

Most Certainly  
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Gotta Love this Forum - LOL

In all honesty, I would just use ND Honda 750 Gauges

I think you might find their not identical
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You're probably right - I still run my original Laverda ND's: but what does it take to make the Honda ND's compatible - they sure look identical - Speed-O and Tech that is - Perhaps gearing and say a resistor or two?
 
The internal gearing ratio of the Honda Tach is not 1:3, idiot lights are not present on early CB500/550/750 instruments and the backing cups/mounting is different.
 
Laverda SF said:
Gotta Love this Forum - LOL

You're probably right - I still run my original Laverda ND's: but what does it take to make the Honda ND's compatible - they sure look identical - Speed-O and Tech that is - Perhaps gearing and say a resistor or two?
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One instrument has a 3/1 drive, the other, 4/1, forget which is which.

Early twins with 30 mm carbs and original filter rev out fine, probably because the system isn't airproof so air gets in a lot of places other than through the filter.
I've always found those early twins to be forgiving as far as carbs are concerned and not too worried about belmouths, filters etc though pod type filters would be another matter.
Paul
 
Laverda SF said:
Keith: What 750 Twin could rev like the Breganze 750 back then other then the Honda 750 4 - reaching 10G - But it fell apart, like the Commando, and handled like shit - not saying the Commando handled. That's why I bought a Breganze and 40 years later it's still revs better then ever. Sorry Duke Desmo 750SS's but you'll never catch me within a mile or 2 - That's if you can hold on. Gotta say Desmo's really perform when their HOT so Beware.

Definitely the Breganze 750 is one of the BEST 750 Twin's of All Time and a Worthy Collector's Item providing we care and have the courage to ride them.

3 Cyl Laverda Guys had better LOOK OUT - Yah! I can hit 128+ mph ; but you may have to do more to get bye me,  STILL running the old VHB 30A's Open Mouth.

The Biggest Shock to any Enthusiast's is that I'm running Open Carbs ;o)
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Hey - this is my first post  :) Seem to be a nice forum.

I have a SF750 in my garage that has been resting for too long.
Lots of work, just have started to take inventory..

Anyway - thanks for the enthusiasm, Laverda SF ! It really made my day  :D
 
Well I got the bike running just fine with reliable tickover easy starting and so on but on the other hand I soon found out that it smoked heavily from the exhaust. I wondered why my mates got so far back when we rode together, I just assumed they didn't keep up...

I blamed myself for not remembering if I had put the seals on the intake valveguides so I pulled the head off to have a look and found out that there was no seals. I also found out why, because the valveguides have a larger diameter outside than the later ones. Now, I don't know if there are seals for those "big" valveguides, but if there aren't, what do I do?

I've used new headgasket and torqued everything properly. There are new pistons and rings.

Easy fix please!

David
 
Peerless said:
Well I got the bike running just fine with reliable tickover easy starting and so on but on the other hand I soon found out that it smoked heavily from the exhaust. I wondered why my mates got so far back when we rode together, I just assumed they didn't keep up...

I blamed myself for not remembering if I had put the seals on the intake valveguides so I pulled the head off to have a look and found out that there was no seals. I also found out why, because the valveguides have a larger diameter outside than the later ones. Now, I don't know if there are seals for those "big" valveguides, but if there aren't, what do I do?

I've used new headgasket and torqued everything properly. There are new pistons and rings.

Easy fix please!

David
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Afraid there is no easy fix, David.

While guides can be modified in situ to take seals, you'll need to find somebody with the equipment to do it.  It can be done on Serdi valve seat cutting machinery (done it a few times), probably on others as well.

On the other hand, if the engine smokes badly, the guides might be shagged and due for replacement anyway, in this case the later guides and seals can be fitted.  A rattling cylinder head is one sign of worn guides...

Takes a long time for stock factory twin guides to wear to the extent that they cause excessive oil consumption, lots of engines still running happily without the seals.

Were the cylinders bored and honed correctly to suit the new (oversize?) pistons?

piet
 
Hi Piet

I checked the guides and they where well within the tolerances. The liners are new and professionally installed and honed. The pistons, standard, are a tad on the small side but the shop said it would not be a problem. Maybe it is after all.

I have an empty head for my SF1 project, Ill probably check the guides in that and swap heads.

What maximum play would You say is OK with the pistons and liners?

David
 
What maximum play would You say is OK with the pistons and liners?
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Granted closer of piston to a true parrel Cylinder Wall clearance with correct ring gap will make for a longer lasting engine; BUT, you would be surprized how well a .005" over Piston to Cylinder Wall clearance using .030" over sized Rings on a Stock Dia Piston gaped to specs will work. The honing is critical that you do it slowly with a 45 Degree Cross Hatch and by measuring ring Gaps ensure the Honing results in a Bore that is truly Parallel so the rings do not change gap while riding the bore.

If the origional Pistons are good but you have worn rings with cylinder bores that look like this ")(" the above method will last for a few years without having to buy over sized pistons and re-boring or buy liners.

Racers will use a fair amoung of Piston Skirt to Cylinder Bore Clearance and Piston Slap is noticable on start up until the motor reaches operating temperature.

I would say .005" to .008" maximum as long as you hone the bores true and gap oversized rings to specs.
 
If you checked guides and they were OK, that's not where the oil smoke is coming from. You don't really need seals on them and certainly not worth getting the head off just to put seals on the guides.
Have you checked compression?
Have you not overfilled with oil?

From memory, piston to bore clearance is 0,08 to 0,1 mm.

Ciao
Paul
 
That?ll be max clearance, Paul.
Make sure the breather isn?t kinked or somehow blocked, rubber ball acts as a one-way valve. Quick and easy to check.
 
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