Rear brake pulls bike to the right

[pckopp]

1978 Special, 12K miles

Rear caliper rebuilt, bronze swingarm bushings installed, all greased and lubed. Rear wheel bearings good and the chain is aligned with proper slack.

When I apply the rear brake alone it feels like the rear of the bike is pulling to the right. If I apply both front and rear brakes together it does not do that. Or if I keep some throttle applied and apply the rear brake it doesn't do it. The rear wheel is not breaking traction, ie. not skidding.

Is this just normal frame and swing arm flex or do I need to look for something else? There is no lateral play in the rear wheel but if I really push/pull hard I can flex the swing arm.

The bike really runs great otherwise. All stock except for handlebars.

Thanks!

 

[fredintoon]

Hi Phil,
my best guesses in order of likelyhood:-
1) The back wheel is pointed a little to the left.
2) It ain't happening, it's psychosomatic.
3) Your sense of balance is shot and you should add a sidecar.

 

[TwoManyXS1Bs]

I recall a similar scenario, caused by rear axle shift. The axle nut achieved a false torque because the axle bottomed in the adjuster before actually clamping the wheel. This isn't the thread, but has revealing info:

http://www.xs650.com/forum/showthread.php?t=34841

 

[pckopp]

I recall a similar scenario, caused by rear axle shift. The axle nut achieved a false torque because the axle bottomed in the adjuster before actually clamping the wheel. This isn't the thread, but has revealing info:

http://www.xs650.com/forum/showthread.php?t=34841

Interesting read. I will pull the rear axle tomorrow and double check that all is correct.

Thanks!

 

[gggGary]

+1 get back into the rear axle spacer bearing assembly.

 

[pckopp]

Fixed!

The rear axle was not completely tight. I could spin the axle with a screwdriver in the right end. Only took one flat on the castle nut to get it correct. Several trips up and down my street to verify.

I must be much more careful during assembly.

Thanks to everyone. This forum rocks.

 

[mrtwowheel]

That's what I thought your problem was, I didn't post because I didn't want to sound like a "know it all". HA !!! I had the same thing happen on a Yamaha XJ, blamed it on the spaghetti swing arm for a while until I adjusted the chain and couldn't tighten the axel without spinning it around. One washer can make a big difference.

Scott

 

[weaselbeak]

I have seen that happen on a wire wheel with loose spokes that allowed the rim to twist. I assume you have a mag wheel.

 

[pckopp]

I have seen that happen on a wire wheel with loose spokes that allowed the rim to twist. I assume you have a mag wheel.

Yes, 78 Special.

Really stupid of me to not check the axle tightness. Lesson learned!

 

[5twins]

Yamaha gives torque values for the axles in the shop manual. The front isn't too bad at about 60 ft/lbs but I feel the rear is a bit much at 108 ft/lbs. There's also the fact that these values are given as a single number. That just doesn't make sense for a slotted castle nut that needs to be aligned with a hole in the axle for a cotter pin. Set the nut at the exact figure given and chances are slim to none that the nut slot will be aligned with the axle cotter pin hole. No, what should have been speced is a torque range for these castle nuts, allowing some movement of the nut to align it for the cotter pin, and still have it remain in the given range. Well, I think I've found some suitable specs listed in the XS500C manual. That bike used the same size axles as the 650 (along with many other fasteners) so I think these specs can be applied to it. I "doctored" the chart a little, adding the single value 650 specs in the last column. As you can see, they fall within the spec range given for the 500 ......



I don't usually torque my axles, just make them reasonably tight and aligned for the cotter pin. However, now that I've found a range to work within, I may try it. I'll start with torquing the castle nut to the minimum spec, then hand tighten just enough more to align things for the cotter pin.