Swingarm not moving freely on 750SF

D

denoiad

Full member
Is the frame supposed to squeeze against the swingarm bushing when the swingarm spindle nuts are torqued down to spec at 40ft/lbs?

at 20-25ft/lbs the swingarm moves freely.  Once I'm up to 40ft/lbs it stays in whatever position you leave it at and it takes some force to move it.  I'm wondering if this is normal and a built in damping feature  of if there is something wrong. 

The swingarm bushings have a steel sleeve which protrudes out from the swingarm about 1/'8' or so.  This is the part that is touching and binding on the frame when tightened.
 
If the swing arm is binding on the inner pins then it is the bearings that are binding, it is free to turn when the pivot stud is loose because the arm is pivoting on the stud. Best to take it all out and clean and check the swing arm bearings, if it is all ok then reassemble with fresh grease. If the bushes and pins are worn you can either fit needle roller bearings from the later bikes or replace the bushes. The arm should move freely through its full arc.

  Keith.
 
On all the SF1.2.3 the inner spindle is one long tube running in bronze bushes. Maybe the earlier ones were in sections. Regardless, the bushes must pivot freely on the inner when tightened with minimal end float. As you say the spindle is proud of the bushes, as it should be. How much it protrudes determines end float of the swingarm in the frame which should be as little as possible without binding. Make sure the spindle is well greased and isn't siezed in the bushes. Check the frame where the spindle sits that it isn't sunken in allowing the frame to bite on the bushes when tightened. I have encountered your problem on bikes where the swingarm has been painted without masking the outer flats of the bushes, the paint thickness enough to cause binding.
 
The pivot was removed along with the swingarm, cleaned and greased.   

I have the rubber bussing model 750,  no brass bushings or roller bearings. 

The swingarm moves freely through its full arc as smooth as can be until i tighten past 25ft/lbs of torque.  At that point it start binding on the framemore and more until i hit the spec of 40ft lbs. 

I would remove the rubber bushings and replace but they seem like they are NOT coming out.  Frame looks fine.  I dont think its a paint issue,  the area where the frame and swingarm touch has been worn down to bare metal through the black frame paint. 


Any ideas???
 
Here's some details of a modification I carried out to help ensure that the lateral loading on the swingarm is nicely controlled and easy to set up. It's not a particularly easy conversion to do but it might be of interest to some;
I bought some very high quality INA needle roller bearings which have a ball bearing thrust race built into them forming a top hat shape.
I trimmed down the outer edges of the swing arm by 7.5mm to compensate for the extra length of the bearing [no going back at this point!] , a thin steel sleeve had to be made in order to reduce the ID of the swingarm so that the bearing would fit. Internal sleeves are available for these bearings so that a standard swing arm axle can be used.
I opted for a sleeve with a larger ID and have made up a hollow 17mm axle from EN16T.
Like I said, it's not a 5 minute fix but it provides a very accurate and positive location for the swing arm.
 

 

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Wow nice very nice job on that siwng arm modification.  But i dont think that is in my plans.

I'm thinking of shaving down the steel sleeve that sitis inside the rubber bushing (the piece that rubbbing on the frame)  I'm estimating 1/100th or 2/100th of an inch off will solve my problem.    I dont want to do this though because i dont think its a proper fix.  There must be something else wrong but i just can figure out what. 

Unless, the rubber bushings were replaced by the previous owner and were not pressed in far enough??? 
 
Hi Daniel,
I was wondering about your problem and don't think that trimming the internal sleeve will help. If you think about it the internal sleeve will get clamped tight between the internal spacer and the frame when you tighten up the swing arm bolts and is designed not to move. The movement is provided by the rubber bush. The drag [I think] is being caused by the swing arm fouling on the frame when the bolts are tightened. If you reduce the length of the bush's inner sleeve you will probably increase the problem rather than alleviate it.
You might want to check that torque wrench....
Bob
 
Daniel,

What you are reporting is quite normal...... as Bob states, the rubber inside the bushes provides the movement.  DON'T trim anything off anywhere!  Just install, mount the shocks and THEN tighten the swingarm axle.  The inner sleeve shouldn't rub, it must be tightly clamped to the frame!

Once everything is tightened up, the rubber is loaded torsionally when the swingarm moves.  The arc of the swingarm is small enough not to damage the rubber.  The rubber also offers a (very) small amount of extra damping!  BTW, the bushes within the shock mounts work in exactly the same manner. :wink:

The rubber bushes actually work quite well and last almost indefinitely.  Unless they are seriously decayed and you are experiencing excessive movement under hard acceleration, there shouldn't be a reason to swap the bushes for needle bearings.... and, as you already have found out, they're a bastard to remove!!

HTH,
piet
 
I attached a drawing just to make sure we are all on the same page. 

The steel sleeve is what sticks out wider then teh bushing or swingarm itself on both sides.  I think this is normal as it would rest against teh frame and sandwhich teh swingarm in place so it doesnt have any lateral movement.    The problem is the frame is sandwhiching it too tightly and its binding up.     

Just to Clarify the rubber bushing not the steel sleeve moves,  they are solid to the swingarm other then a slight twisting of the rubber under heavy load.  The sleeve is greased as well as the pivot bolt and that that is what the swingarm slides on when it moves up and down. 

So if i decided to shave down teh steel sleeve by a 1/100 of an inch or so, how would that aggrivate the problem?  it should allow some space between the fram and sleeve so it doesnt bind no?
 

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hi
the sleeve should be clamped solid between the frame and not be able to move/rotate at all.the movement is in the rubber bush twisting in a radial plane,that's why on motor car wishbones they are tightened with the vehicle on the ground and the suspension in its natural position not hanging down,the same would apply to the swing arm
neale
 
Daniel,

You DON'T need any space between the frame and swingarm bushes!  The entire bushing/swingarm assembly should fit SNUGGLY into the frame.  When the swingarm pivot bolt, which it isn't really, is tightened, the frame should not be stressed in any manner.  By all means grease that threaded rod, that will prevent it from rusting solid, but the swingarm does NOT pivot around it!!!  It pivots around the sleeve within the bushes, and the sleeves must be tight to the frame.  THE FRAME IS NOT SANDWICHING IT TOO TIGHTLY!!  The twisting of the rubber is normal.  When the pivot is tightened, it should pinch the bushes within the rubber, the distance tube that is located between LH and RH bushes and the swingarm mountings, making for a solid "axle" about which the swingarm can move through the movement offered by the rubber in the bushes.

If the axle/pivot bolt or whatever you like to call it, is not tightened, the swingarm can and will move around excessively on it and the holes in the frame will be damaged.  If you remove metal from the bushes' sleeve, it will allow you to pull in the swingarm mounting plates, stressing and bending the frame.

Please install the swingarm loosely in the frame as it is, loosely install the shocks and only then, tighten the pivot to the specified torque.....finished!!!  That' the way Massimo and Luciano meant it to be. 8)

piet
 
piet
that is correct and clearly explained,wish you had written some of the haynes manuals and all of the BQ and homebase self Assembly instructions :D
neale
 
ahhhhhhhhhhhh now i see!!!!      Thank you for clearing this up,  i didn't realize that is how it worked at all,  i thought the swingarm was supposed to move very very freely over a wide arc from top to bottom.

Thanks again,  now i can assemble properly and with piece of mind that it is correct.

 
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