crank balancing, balance factor

[hein weijers]

Last year I had the crank of my Triumph Bonneville balanced by an old specialist in England and the result was great! He removed the con rods and pistons and replaced them by 2 bob weights on the crank journals, taking in account what balance factor I wanted.

This was the result.

I am wondering how an XS crank is balanced. It is not possible to split the conrods, so how is it done? Has the crank to be taken apart several times before the job is done?

Hein

 

[inxs]

- Hein the man to talk to i think is Herbert Clären or perhaps Karlheinz Graf

 

[xsjohn]

Had one of mine balanced a few years back....an 80......idoled smoothly but still vibrated above that......not what I expected..........and expensive....has to be taken apart 2 times .....bobweights then putting the rods back on.......should be welded.......other ways to smooth mine to suite me have been more successful and practical and way cheaper than the balance........

xsjohn

 

[hein weijers]

Doesn't sound like an easy job!

He, Xsjohn, could you tell us about the secret ways to smooth an XS?

Hein

 

[xsjohn]

Hein...........might want to read over this thread...........

http://www.xs650.com/forum/showthread.php?t=1128

Working the timing retarded about .168 thousands...so it runs like a normal engine from 2-4K...not setting it advanced too much at 2500-3000 rpm....working the springs if necessary also.....(TCI makes all this easier) I suppose with the ATU after retarding one could cut the back side of the weights so it would fully advance over 4K for those that just have to rev the snot out of them....gear it taller so it doesn't have to rev when cruising...............

Most are still like a monkey with their hand in a jar to grab something........won't turn loose of anything for fear of losing what's in the jar....even when they are not sure whats in the jar anyway............

xsjohn

 

[Sundie]

Is it mayonnaise?

 

[xsjohn]

No..........it's a turd...........and most will have to stick their hand in there many times before figuring it out.........finally got the smell off my hand myself.....

xsjohn

 

[hein weijers]

Thanks John, that's interesting stuff. The problem is that I have a rephased camshaft. The chainwheel on the camshaft is locked with 3 bolts. Lowering the pistons would be a better option in my case.

Hein

 

[xsjohn]

Hein........are these standard compression yamaha pistons you have.......looked at removing some from the dome........6MM in the center is pretty thin but somewhat off the center on the valve indent seems to be plenty as you get off the center if you look inside..........could first measure and balance the pistons......heavier to the light one on a gram scale.....then remove and remeasure the weight as you go.......sounds like a lot of hassel there too........and if they are high compression popups it may not be possible to get to 8-1 ..........

The custom chainwheel .....could take some like .030 thousands out of the side of the holes to retard the cam and back fill the other side.....then go up onthe head .040 thou......I still like the fact that going up tightens the cam chain back to stock and the whole thing is easy to back out of if it doesn't suite you......

Also .168 thousands ignition retard on the TCI makes the thing work down low.....how that relates to the ATU is something you would have to play with...(as described ionthe post above)...keeping in mind that standard advance keeps these week even a 2500.......and mine pulls off now just above idol in the lower gears and cruises great.......

xsjohn

 

[hein weijers]

I am just an old Dutchman: what does ATU mean?

Hein

 

[Trebor13]

advance timing unit.
i think, but i'm also a dutchman, so what do i know????

 

[marcus243]

thanks,is anyone out there know which cranks are interchangeable with 70 model xs650

 

[XSRob]

Think 70-73 cranks should work. Your rods should be 256 so keep clear of 447 and 533 rods!

 

[marcus243]

well the crank i have has 447 on them,the engine number is s650208864,maybe someone could tell which model this is.

 

[grizld1]

Your 447 crank will install just fine in early cases, even XS1; just be sure to use pistons with 20 mm. wrist pin holes and an 18t sprocket on the camshaft.

 

[XSRob]

Thanks grisld1, thought there might be more difference than sprocket size and rod length/eye diameter etc. Good news if I have a problem on my early motor

marcus243, there is this one on E'bay:
http://cgi.ebay.co.uk/yamaha-xs650-/250731504370?pt=UK_Motorcycle_Parts&hash=item3a60c322f2

 

[marcus243]

thanks for the offer but the engine i have is a US model, and i found also on ebay for $3.00 just,plus i have family in the states that will ship it with other items i ordered from ebay

 

[XSRob]

$3 for a crank, well done. Sounds a good mix of parts you have there. S650 cases, 447 rods and a us model motor (Did the early US motors not have 256 rods?). Was this motor running when you got it? Just interested.

 

[marcus243]

yes it was,but it had broken front mount slot ,think thats a mix i will be putting the engine in a suzuki frame