Swing arm

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Anonymous

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As anyone tried to adapt a "foreign" swing arm on a MK2 (Ducati or even Alu/Jap)? Should be easier to help putting a disc on the back?
Philippe
 

Ron L

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Why not just use a MkIII swing arm? This will mount easily with the MkII spindle. You can then use a MkIII rear wheel and disc. Be sure to use a MkIII speedo drive.

I put an entire MkIII cradle, swingarm and wheel in my '73 Interstate. It required slotting the upper transmission bolt hole for primary chain adjustment. This way I could use the better swingarm spindle retaining system and got the vernier isolastics as a bonus. A small master cylinder can be mounted above the fender on the frame and actuated by the cable from the left brake pedal. It's a pretty transparent swap. Most people look at the bike quite a while before they notice.

Would I do it again? Probably not. I had the pieces laying in the shop, including the speedo drive, axle, and wheel. If you have to buy all that, it can be pretty expensive. You don't gain much at the rear wheel as far as braking power. The front does most of the work anyway. You do get the strongest of the three versions of Commando swingarm. However, you still have a two-piece axle. Convenient for pulling the rear wheel, but weak when racing or adding horsepower.

Ron L
 
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A few years ago at the Norton tent at Mid-Ohio a man had adapted a full mono shock set up off another brand and still retaned the transmision engine cradle. It was a real clean job, anything is posible most who modify the rear are after wt saving not braking. norbsa
 

Anonymous

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Swingarm

Hi, Ron. I did the same as you (and I probably wouldn't do it again either) but I used a modified MK3 master cylinder under the seat. I'm unhappy with this, so I want to know, what kind of master cylinder did you use and where did you get it? Got any pix?
 

Anonymous

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Dwardo,
I used a Hurst-Airheart master cylinder from and old dirt tracker. These are small and easy to mount and I often see them available at swap meets. Seal kits are hard to find tho.
Ron L
 
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Some time back there was a controversy over the adapting of needle bearing/ conversion for the Norton swingarm.
The site, www.nortons.com , but gave over more to rumour and myth despite my best pursuits..

The gentle- man I chased up was one "Dynodave" who has his own Biz and website, but at that point he had no positive resolve.
But it does sound feasible and a great inovation!..
 
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As I see this problem of swing arm slop it is not really a failure of the bronze bushings so much but the lack of support were the shaft passes through the cradle. The cradle is just not up to the loads put on it. Lets say that the neddle convertion would fix all the lube problems and provide a life time of stable support. You still have the shaft passsing through this cradle that can't take the load and that is the thing to go after. I have about 3000 miles on a brand new swing arm, shaft and bushings and I am already feeling the slop develop in the cradle. a repair that could be carryied out without ripping it all down would be a good thing. Anyone got any bright ideas. norbsa
 
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How about those collars/lockscrews that Heinz Kegler developed? You can read about it on the NCNOC website. Go to www.nortonclub.com, click on Tech Articles, and read Swing Arm Repair. Sounds to me like that would solve the problem and all you have remove is the rear wheel.

Debby
 
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Yes that repair can be done many different ways. Since I had it all apart any way I choose to do the welded modification. I am talking about something else here. It's were the now stabilized swing arm shaft passes through the cradle and the egging out of those holes. This is why over size swing arm shafts are offered not for the swing arm repair but for cradle repair. norbsa
 
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norbsa I am NOT fond of the nuts welded on bodge. if you look at the stress that is put on the tube in such a small area such as the weld than the split collers look nuch better. the load is transfered to the frount of the tube and a MUCH larger area along with opposing forces on the tube now. I seen that clubman racing will be offering a swingarm that is made out of oval tubing and uses 2 ballbearings on each side insteed of the bushes.

bill
 
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Yes Bill it's a better fix no douwt. But it was not around when I did my Bikes. So I just did what the tech digest said. I was able to get the slop out of my rig today by dropping the oil filter assm. and snugging up those screws. I was just fishing for someone who may have come up with a way to put in some hardened bushings into the thin cradle so I could fix it for longer time . norbsa
 
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norbsa the better way to fix it if you had the time and resores would be to make a jig to mount the plates in than cut out the tube, oversize the holes and put in a LOT thicker wall and harder tube. but the real problem as i see it was the support was WAY to narrow to start with. if the primary was not in the way outriggers for the pin would shurly be a BIG help to.

bill
 
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