head scratcher

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seattle##gs

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MK3 Norton. The swingarm is approx .250 wider than anyone else's. Does not appear to be altered in any way. All parts, appear to be stock, the wheel bolts up well and the bike rolls along with no problem. I have another MK3 nearby to compare to.
If I pull the wheel and brake assembly to the right, the disc and caliper will line up, but there is approx .250 extra room on the left side. I could cut a spacer to fit.
However, since I removed the primary to replace the GB seal, I put a straight edge on the two sprockets and the are out of alignment by the width of the spacer. Also, the tire appears to be offset in the frame. So it seems the only way I am going to get things to line up is to cut a spacer to fit between the hub and the brake disc. Possible but I don't have any idea why I have to do this. Anyone run into this? I'll bet no one has.
 
Possibly someone jacked it apart when they couldn't properly fit the wheel and associated parts into place? Would be pretty dicey to try to pull it back to the original distance. If your rotor spacer does the trick, go for it, as long as everything functions as designed.
 
Given a choice, I would line up sprockets.

There has to be reason for this .... try laying a straight edge along each arm of the swing arm. It is possible one arm may be bowed outwards. I had a similar problem on my Atlas, only the drive side arm was bowed 0.140" inwards. In my case, forcing the swing arm open would spread both arms nearly equally, leaving the sprockets 0.070" out of alignment.

I found the only way to take out the bow, was to remove the swing arm, put it in a hydraulic press properly braced either side of the bowed section, and pushing on the high part. Finding exactly where the arm deviated from straight was crucial to the correction procedure.

The proper swing arm inside distance between wheel mount flanges is 7.875 - 7.90 inches for the Featherbed frame, and the Commando is about 1/8 " more. Check out the exact specification for the Commando and shoot for that number if you find swingarm correction is necessary.

Slick
 
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As the spindle and axle assemble well and vital to get sprockets and disc rotor spaced/aligned - I suggest first custom spacer for sprockets in line then hub mount spacers for brake rotor to center then forgetaboutit.
 
seattle##gs said:
MK3 Norton. The swingarm is approx .250 wider than anyone else's. Does not appear to be altered in any way. All parts, appear to be stock, the wheel bolts up well and the bike rolls along with no problem. I have another MK3 nearby to compare to.
If I pull the wheel and brake assembly to the right, the disc and caliper will line up, but there is approx .250 extra room on the left side. I could cut a spacer to fit.
However, since I removed the primary to replace the GB seal, I put a straight edge on the two sprockets and the are out of alignment by the width of the spacer. Also, the tire appears to be offset in the frame. So it seems the only way I am going to get things to line up is to cut a spacer to fit between the hub and the brake disc. Possible but I don't have any idea why I have to do this. Anyone run into this? I'll bet no one has.
Click to expand...

That right hand side of the swing arm can be easily/accurately/safely pulled back into place. A 6' x strong enough channel/angle iron/pipe suspended inside the arm, a short length of chain attaches it to the arm at the axle slot area, the end goes in near the crotch of the swing arm. Pad with an old leather glove. 2 stout lads (feed & beer them) to hold the bike from pivoting, and give increasingly stronger pushes to the left on the lever, measure between each one. Smooth & easy, no drama.
 
I can't imagine how the swing arm could be bent. Isn't it supposed to be stronger than the previous ones? If there was a big accident the rest of the bike doesn't show it.
My problem with making a spacer between the disc and the wheel hub is that I will have that much LESS thread engaging with the dummy axle.
I think the problem is with the right side of the swing arm. On the left side (if I take out my spacer and bolt up the sprocket/brake assy normally) the sprocket lines up with the gb sprocket. Anybody have a spare MK3 swing arm for sale?
 
seattle##gs said:
My problem with making a spacer between the disc and the wheel hub is that I will have that much LESS thread engaging with the dummy axle.
I think the problem is with the right side of the swing arm. On the left side (if I take out my spacer and bolt up the sprocket/brake assy normally) the sprocket lines up with the gb sprocket. Anybody have a spare MK3 swing arm for sale?
Click to expand...

Yeah, putting in a spacer that blows yr sprocket alignment AND give less thread engagement doesn't sound that attractive to me, either.
Please keep us posted.
 
not without taking off the rear wheel. I had a previous thread on this subject several months ago, now I am back revisiting the problem because I have all the primary stuff removed and can now see clearly that the sprockets are out of alignment.
 
"I can't imagine how the swing arm could be bent. Isn't it supposed to be stronger than the previous ones? If there was a big accident the rest of the bike doesn't show it."

It didn't have to be trauma.
It'll bend easier than you think.
 
concours said:
"I can't imagine how the swing arm could be bent. Isn't it supposed to be stronger than the previous ones? If there was a big accident the rest of the bike doesn't show it."

It didn't have to be trauma.
It'll bend easier than you think.
Click to expand...

I'll testify to that! Damnfino how mine got bowed, but it damnshuredid.

@seattle##gs, lay a straight edge on it. I am with you.... I think the problem is in the right arm.

Slick
 
Do note the chain side arm is runs almost straight back while the other arm angles out more for wheel width clearance. I have dealt with bent swing arm to know it skews both axle and spindle holes alignment once freed. Famous go to frame straighener could not get it to pass a spindle again, so had to get another. No way to spread the ends by crashing as fastened together so only area that get sprung is the spindle and brace tube area. Someone with a buddy must of laughed asses off as they carefully set up your swing arm prank to pass axle and spindle but too wide at end, thus displaying great metal heating jigging skills anonymously.
 
I a m buying another one off ebay,let's hope it is a good one. When I first got the bike I could tell there was something wrong with the back end but I figured I could solve the problem if I put in enough hours. The caliper holder had been ground on with a disc grinder and japanese axle draw bolts had been fitted. I replaced those with new Norton parts. Do not recall if the swing arm had a lot of tension in it or not. I don't think it would be possible to squeeze the swing arm .250 with just the axle.
 
"When I first got the bike I could tell there was something wrong with the back end but I figured I could solve the problem if I put in enough hours. The caliper holder had been ground on with a disc grinder and japanese axle draw bolts had been fitted. "

The plot thickens.....
 
concours said:
"When I first got the bike I could tell there was something wrong with the back end but I figured I could solve the problem if I put in enough hours. The caliper holder had been ground on with a disc grinder and japanese axle draw bolts had been fitted. "

The plot thickens.....
Click to expand...

You most probably know this but, the Mark 3 swing arm does use chain/axle adjuster draw collars. Check the wrench size needed for the adjuster bolts and lock nuts.
The rear brake caliper holder plate does have a recessed portion cut into it.
 
Well, I rolled up my sleeves and dived into the project. After a WHOLE LOT OF WORK, the chain now lines up, the wheel is turning freely and the disc lines up in the center of the caliper. Because I now have less thread engagement on the axle I will cross drill the hex on the axle and safety wire it. Reminds me of the time in Yerington NV. I was following behind a friend who was riding a MK3. I happened to notice the rear axle was backing out so I waved him over and we screwed it back in.
 
Is this the swing arm from ebay, or did you line up the caliper using a spacer?

I am curious to know what is at the root of the problem.

Slick
 
The one on ebay was not a MK3 so I cancelled . I ended up shoving the entire wheel and disc assembly to the left. The sprockets then lined up I made two spacers, one to take up the extra distance on the axle and one to move the disc to the right. Still no idea what is the reason for the extra wide swing arm. I will probably never know.
 
I bought another swingarm off ebay...very cheap. It is in great condition...only problem is that it is even wider than what I have. Didn't think it was possible. It measures 8 1/2" inside measurement tip to tip. I have two MK3s here and lined it upon their swingarms. wider and way wider. I'm willing to make someone a fantastic deal on a swingarm that is too wide. Good for garage art.
 
Are you sure you don’t have a spacer, or similar, missing? Or perhaps even undersize?
 
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