Things I've discovered about the swingarm/driveshaft

[Rusty McNeil]

In a recent post it was discussed about the rear spline joint being able to handle a little offset due to the way it was manufactured (it's kind of a wobble joint; hard to describe but if you looked at it closely it's real obvious)

And how this would lend itself to being able to use the swingarm pivot bolt and nut the right hand side of the swingarm on both sides of the bike so that offset can be adjusted left or right a "little" bit...

Well, I spent the last couple of days notching and bracing my swingarm (pictures to follow; it turned out real nice) and in the process learned that;

The driveshaft ALREADY operates at a slight angle in stock configuration, hence the reason it's got a wobble spline joint at the pumpkin

1. There is about 5-6mm (I'm being generous, it's probably a little less, less than a pencil width, at least on my 99) available left-right movement in the stock set up between the stationary swingarm mounting points; stock setup being all the way to the right

2. If you wanted to do this swingarm adjustment I think you could simply swap the pivot bolts from side to side and push the swingarm as far to the left as the stationary mounting point would allow.

But;


Moving the swingarm to the left brings the driveshaft CLOSER to the inboard side of the inside of the driveshaft tube. and it's already pretty damn close, With an unnotched swingarm it probably wouldn't touch, On a notched swingarm I don't see how it could not end up rubbing the driveshaft on the inside wall of the swingarm.

Before pulling my swingarm I drilled a 1/4" hole in the factory swingarm indentation at the high point in the center (center being front to middle and top to bottom of the indent) of the indent where the driveshaft passes by, I did depth check and the driveshaft was 1/4" away from the wall at that point, as you go further toward the engine the driveshaft is more like 5/32"-1/8" away from the wall of the driveshaft, moving the notched swingarm to the left using the method described above would have had the driveshaft it touching the inside wall....

I remounted my swingarm after cutting out the notch and did some measurements and about the only thing avaliable in notching is getting rid of the high spots in the indentation that's there from the factory, I ended up with the new notch plate just slightly deeper than the plane of the indented spots in the original setup, which is just enough to mount a 200 tire, which I have on order.

With my Venom-R 180/55-18 I've got just about 5/8" clearance on the left side, waiting for my new tire....I should have about 3/16-1/8" clearance with the 200 tire....

Hope this info is useful for anyone thingking options for modding the stock setup...

Rusty

 

[gleno]

Good info Rusty.

This means selection of an after-market rear rim needs to be a careful choice. Swapping pinions from side to side or putting adjustable pinions on both sides of the swingarm won't necessarily give you the adjustment you need to counter any inherent offset in the rear rim if the shaft doesn't have the clearance.

 

[maxcruiser]

Good info Rusty!

Agreed that this will not completely fix the offset problem, but it will help align the front and back tires, which can be off on some bikes.

Mike

 

[one2dmax]

as he noted you can gain close to 1/4" shift from that move. Once you get a larger driveshaft you won't get that much. The "Otec" brand swingarms include two new close tolerance adjustable pins since they actually need to be adjusted farther to the left to keep the driceshaft from rubbing the thicker walls of the aluminum arms they make.

Sean

 

[gleno]

as he noted you can gain close to 1/4" shift from that move. Once you get a larger driveshaft you won't get that much. The "Otec" brand swingarms include two new close tolerance adjustable pins since they actually need to be adjusted farther to the left to keep the driceshaft from rubbing the thicker walls of the aluminum arms they make.

Sean

I know I had some doubtful moments when I fitted the OTEC swingarm to mine.

I actually slipped a looped string line around the shaft and then slid it along the shaft to see whether the shaft was clearing the swingarm walls. :whistlin:

It was tight. I used the UFO maxdaddy rear wheel, left the pinions at standard settings and the wheel offset is just about zero.

From what I've seen of some the aftermarket rear wheel offsets on some the forum members bikes they just don't have a way to correct if the shaft clearances are so small.

 

[lankeeyankee]

as he noted you can gain close to 1/4" shift from that move. Once you get a larger driveshaft you won't get that much. The "Otec" brand swingarms include two new close tolerance adjustable pins since they actually need to be adjusted farther to the left to keep the driceshaft from rubbing the thicker walls of the aluminum arms they make.

Sean

What do you mean by larger drive shaft
Are you talking larger in diameter Hmm I dont think I would want that in all the years with my VMAX I have only snapped one drive shaft
I would think Yamaha designed it this way to prevent any gears from twisting or shafts snapping in the tranny
Hmm replace a drivehaft 40 mins
Or replace brokens gears and shafts in tranny 30+ hours

 

[gleno]

What do you mean by larger drive shaft
Are you talking larger in diameter Hmm I dont think I would want that in all the years with my VMAX I have only snapped one drive shaft
I would think Yamaha designed it this way to prevent any gears from twisting or shafts snapping in the tranny
Hmm replace a drivehaft 40 mins
Or replace brokens gears and shafts in tranny 30+ hours

Good Point.

 

[Neil-3446]

What do you mean by larger drive shaft
Are you talking larger in diameter Hmm I dont think I would want that in all the years with my VMAX I have only snapped one drive shaft
I would think Yamaha designed it this way to prevent any gears from twisting or shafts snapping in the tranny
Hmm replace a drivehaft 40 mins
Or replace brokens gears and shafts in tranny 30+ hours

Sean is probably talking about the driveshafts in the 3" over Otec's. The longer the shaft the more angle comes into play. Beefier could present clearance issues, but, for another reason.

Neil

 

[one2dmax]

I would normally agree with you but when you use longer then stock swingarms then you are limited to the shafts you can get. Plus the extra length generates more twist and chance for breakage. The thicker shafts help overcome both those obsticals.

I have broken numerous driveshafts (probably close to a dozen) over the years and though it's easy to replace it can be a pain in the ass when your out of town and/or on a ride a long ways from home (happened more then once too).

I have only broken one block that had the shaft broken instead it may have possibly saved the block. In this case I would have loved to have the shaft break. I have had shafts break that took out the rear differential too. Still, it's easier then changing the engine.

Sean

 

[MAXXMAN93-4301]

the longer a shaft is the more tq it can handle allother things being equal. the gear reducton on navy ships have quilled[ hollow shft with another inside ] pinion shafts too lengthen them and increase the tq capacity, these are only 100,000 horsepower so it may have been unneeded:biglaugh:! the flex helps.the prop shafts on the enterprise mad 1 complete turn at the driven end before the prop would turn!!:surprise: