WHAT'S IT WEIGH? QUANTIFYING THE LAVERDA SF2RR



While I've got the Laverda F750 racer torn apart I thought I'd take the opportunity to weigh the different components.

I've got a 2KG electronic scale that weighs to the nearest gram/.1 ounce, a standard spring-type baby scale (repeatable to within an ounce or so) and a 200 pound digital shipping scale that reads to the nearest .5 pound. Where the component parts are small enough (as in the front fork) I'll weigh them on the small scale. I'll try to indicate which scale was used (if grams are shown it has to be the small scale). In addition, where I have similar parts, or do some lightening, I'll give comparitve weights.


The Engine

One of the big modifications to the head this last go around is replacing the stock 8mm stem steel valves with 7mm stem (same as the SFC) titanium valves, along with new valve springs with titanium spring retainers.

Savings: 118 G of reciprocating weight

Here are pictures of the new and old valves.

I've also swapped the stock valve adjusting screws for ROTAX single items which have a floating "foot" on them that should decrease the pocketing of the top of the valve stem.

Total increase in reciprocating weight - 8 G

The Laverda uses two cams, with shouldered collars that sandwich the cam sprocket between them. These parts are fairly massive, so I drilled some holes in them to end up with parts that are slightly less massive.

Total savings in the camshaft assembly - 96 G rotating weight

The camchain tensioner has a rubber block in the tensioner arm that the plunger bears against. The block in the racer was looking pretty second hand (strange how some rubber/plastic materials just doesn't do well in a hot oily environment - and how often they are put there by engine designers!) so I mentioned to Craig that I was going to get some ultra high molecular weight polyethelyne to make a new block. He told me to make it out of aluminum instead, as any compliance in the camchain tensioner seems to eventually cause problems in controlling the camchain slack.

Total increase in weight - 6 G

The roller on the chain tensioner pivots on a solid steel pin. I drilled a hole down the middle of it. Stock roller pin - 34 G Modified roller pin -

Cylinder Studs: The Laverda has 8 10mm cylinder studs that are 12-13" long. A stud should have the unthreaded portion the same diameter as the diameter at the base of the threads. This lets the whole stud stretch when torqued which helps them clamp, and also reduces the stress seen by the threads.

Savings - 10.5 OZ / 298 G

Crankshaft: The stock crankshaft flywheel diameter is 5.71", and the lightened crank Craig did has an OD of 5.125. A stock crank assy with the starter sprag clutch and generator drive pulley (and nut) is 37.5 pounds. The clutch/pulley assembly weighs right at 3 pounds, so the stock crank is roughly 34.5 pounds. The lightened crank is 28.5 pounds and uses an aluminum spacer to mate to the big oil seal in the engine case (the sprag clutch would normally match up to the seal). I'll stick a picture of each crankshaft here when the film is developed.

Savings - 9 pounds (and all of it rotating weight, making the crank easier to accelerate)

Front Fork Assembly

The Laverda uses 38mm Ceriani fork legs from a 750 Ducati in fabricated sheet metal triple clamps (with aluminum stem) that I made). I just got through installing a set of Race Tech Cartridge Emulators to the forks.



Savings: 2@ 9 G = 18 G


Savings: 426 G






Savings in triple clamp and stem assembly: 500 G




Front Wheel


The Swing Arm and Rear Wheel

Total rear wheel/swing arm assembly weight - 58.81 pounds


Exhaust system


Frame




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© 1996-2005 Michael Moore, last update for this page 01 June 2005

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