Crank Shaft Question

[grasshopper]

Ok motor guys.

What is the difference between a "Press Together" crank shaft and a "Plain Bearing" crank shaft?

http://www.faliconcranks.com/cw-list.htm#plain

I'm trying to figure out how much it is to balance the crank and new rods/pistons for my SV and my friend is busy who helps me build my motors.

What work do I get done? I'm buying Knife rods, and sending my crank and pistons down to them to get balanced.

[matt49g]

I'll take a stab at your first question.  A pressed together crankshaft is often found in single cyclinder and two stroke bikes, the connecting rod is one piece and usually uses roller bearings.  The crankpin, bearing and rod are assembled and then pressed(12-50 tons) into the flywheel halves.  The whole assembly is then aligned using lead hammers, straight edges, dial indicators and a vocabulary that would make K3 envious.  The crankshaft is actually three seperate parts, right flywheel, crankpin (connecting rod journal) and left flywheel held together by the interference fit of the flywheels and crankpin.  There are several slight variations and much more detail to this, but I think you just wanted the concept, not a doctorial disertation.   With a plain bearing crankshaft the crankshaft is one piece and the connecting rods are two piece, split at the big end and use plain (friction type in engineering logo) bearing insert, the rod and rod cap are held together with bolts.  The SV650 uses a plain bearing crankshaft. 

As to how much and what work you would want done, you'd have to talk to someone more familiar with Falicons' work and prices to get the most bang for your buck.  How much money will it take?  ALL OF IT!

[Court Jester]

I'll take a stab at your first question.  A pressed together crankshaft is often found in single cyclinder and two stroke bikes, the connecting rod is one piece and usually uses roller bearings.  The crankpin, bearing and rod are assembled and then pressed(12-50 tons) into the flywheel halves.  The whole assembly is then aligned using lead hammers, straight edges, dial indicators and a vocabulary that would make K3 envious.  The crankshaft is actually three seperate parts, right flywheel, crankpin (connecting rod journal) and left flywheel held together by the interference fit of the flywheels and crankpin.  There are several slight variations and much more detail to this, but I think you just wanted the concept, not a doctorial disertation.   With a plain bearing crankshaft the crankshaft is one piece and the connecting rods are two piece, split at the big end and use plain (friction type in engineering logo) bearing insert, the rod and rod cap are held together with bolts.  The SV650 uses a plain bearing crankshaft. 

What he said.

and to just have one rebalanced could make a big differnce. but the more weight you can have shaved off of it and the smoother and easier it will turn th3e more torch and hp you'll see from it.
but be ready to open your wallet. it ain't a low cost upgrade my any means. and some half assed low priced side shop that doesn't know what they are doing can really screw you up if it's not done just right.
Falicon would be your best bet though

[Super Dave]

A certain amount of flywheel is very, very good, though.

Ask the Falicon guys what to do.  They've been doing this for a long, long, long time.  No reason you shouldn't listen to their intution. 

OEM cranks are balanced, but not to the degree that Falicon would do it.

[benprobst]

if you put new rods in the motor, then deffinetly balance the crank. even if you dont put new ones in its still a very good idea. And I would not suggest lightening the sv crank, I talk frequently to many of the top sv guys around and almost none run lightened cranks and most suggest against it. When you lighten the crank, you lose the torque style of motor that the sv has, you have to ride it higher in the rpm range, and rpm is generally the #1 killer of sv motors.

[catman]

Hey Ben nice explanation- i did have charging coils removed(outside the cases) and had digital charger installed- i figured that 3 lbs off the end of the crank would do me well, just have to pay a lil attention to r's- -Got it from Seedworks in Dover Delaware in case anyone's interested! John in nj

[grasshopper]

Thanks for the help guys.