Laverda 750 sf

L

ludiluka

Senior member
Hi there

I have question for guys that races with laverda 750? Do you have stock crankshaft or lighten crankshaft?
Augusto Brettoni told me that he was always racing with stock crankshaft ?? I don't know what to do now :D
 
Hi - A few of us used to race in the eighties/nineties with tuned SF's - some had lighter cranks others kept std weight. The problem we ran into was the splines shearing on the puny 25mm centre pin. I fitted a 35mm pin into triple crank webs and turned down the diameter of the end SF webs - although I didn't know it at the time I was  making the crank similar to the last SFC's. If you keep the standard centre pin make sure it is loctited in place when rebuilt - lightening the crank and reducing the diameter of it will help reduce the chance of it shearing and doing a 180? conversion whilst you are racing it. - Best of luck - Phil
 
wouldn't be keen racing on a stock crank due to the risk of snapping the weak splined centre main pin as Phil has written
best bet is to strip the crank and convert it to the 35mm main pin which are available from Andy Wagner
not certain who else has them now, I bought Wolfgang's last stock last year, maybe Keith has had some more made

as you need to strip the crank to do the machining to fit the press up main pin then while you are there you may as well lighten the crank, 750 crank webs are a breeze to machine compared to the triple crank webs
you can easily remove 3kg from a SF crank which is what we machined from the Twisted Twin cranks we made (5.5kg from the GTL crank)
we reduce the diameter of the crank webs first and then start shaping the crankwebs, we have written a CNC program for the work and do the machining on a Vertical Machining Center which makes it fairly simple to do now

good luck
 
Red, I was thinking about doing this to my newest project, but does the weight reduction and pin size change increase the horsepower enough to offset the cost of doing it. In my post on "hypothetically speaking" I was trying to get ideas on a caf? build with a little engine change to give it some additional attitude. Scott has the engine now and before he starts the rebuild I want to figure out how radical to go.

Clay
 
'71 SF said:
Red, I was thinking about doing this to my newest project, but does the weight reduction and pin size change increase the horsepower enough to offset the cost of doing it. In my post on "hypothetically speaking" I was trying to get ideas on a caf? build with a little engine change to give it some additional attitude. Scott has the engine now and before he starts the rebuild I want to figure out how radical to go.

Clay
Click to expand...

crank work will not provide any additional horsepower but lightening the crank will allow the engine to spin up faster
pin size change is insurance against future crank breakage
all the horsepower gains are in capacity, valve changes, port sizing, cam selection, etc

if you want an engine with attitude then twist the crank, those engines sound and perform great
 
Redax5 Is it possible to get cnc program?

This will be my first crankshaft mod and i am terrified :D so 35mm pin (if i understan correctly this is pin that conrod connect to?) So i need new conrods. What is the best choice? I will get pistones cams valves from Brettoni.
What loctite are you using?


 
ludiluka said:
Redax5 Is it possible to get cnc program?

This will be my first crankshaft mod and i am terrified :D so 35mm pin (if i understan correctly this is pin that conrod connect to?) So i need new conrods. What is the best choice? I will get pistones cams valves from Brettoni.
What loctite are you using?
Click to expand...
Red loctite.
 
ludiluka said:
Redax5 Is it possible to get cnc program?

This will be my first crankshaft mod and i am terrified :D so 35mm pin (if i understan correctly this is pin that conrod connect to?) So i need new conrods. What is the best choice? I will get pistones cams valves from Brettoni.
What loctite are you using?
Click to expand...

The 35mm pin is the central part with the cam chain gear, joining the 2 halves of the crank.
Paul
 
Ludiluka. A standard crank will be fine for some club racing with a bike that isn?t very highly tuned, overbored etc. Many people have done many seasons on them without trouble. My mate raced with the standard centre for about 10 seasons before the centre gave way, and it didn?t wreck anything else when it went, just needed replacing. His bike is also very highly tuned and has 90deg firing with a "big bang" configuration (firing pulses 90deg apart with almost 2 revolutions before the next firings, so very stressed). Of course the best thing is to do the big pin conversion, lighten and balance it with Carillo rods fitted etc etc. It really depends what level you want to race at and how much you want to spend.
 
Well it will be long project because finances but when i do something i want do do it wright. :D first i have to modified frame but i am still searching 38mm cerianis
 
Is there anyone that is willing to share knowledge about crankshaft lightening. I want to make 270 degree crank ?
formulas for calculations,...
 
I used a 65% balance factor on each half of mine. This was over 20 years ago - so I expect now that ideas may have changed a bit these days, Bike is really smooth with a bit of a tingle at very high RPM - Regards - Phil
 
Need help again. Can somebody measure dimension on photo. I’m not sure if my part is worn out or not. Also does anybody have this part for sale

D43925FF-ABB4-4D6F-A000-DBEE18FA453A.jpeg
 
Paul Marx said:
Worn out?

Paul
Click to expand...
Somehow gears got destroyed during riding. after dissasembly there was a lot of metal mixed with grease,... i just want to check that everything is ok before installing new gears. bottom bushing in wheel cover is for sure worn. Shaft diameter is 5,45mm and hole in bronze bushing is almost 6mm.
 
You must log in or register to reply here.
Back
Top