MK3 Restomod

lcrken

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Looking at the Phil Pearson and NEB clutch baskets, there is a potential for saving another 1.5 kg / 3.3 lb or more by replacing the stock basket by one made of aluminum. This is another Mk. 3 part crying for a modern replacement (I am not considering a belt drive).

-Knut
I wouldn't recommend using an alloy clutch basket with the MK3 chain drive primary. A couple of decades back I tried using an alloy engine sprocket and clutch on a 750 Commando racer, and the sprocket teeth on both wore out almost immediately. I think it was from Fair Spares, but I'm not sure after so many years. It might work better with one of the modern high tech surface treatments to provide a much harder wear surface. I don't think the one I tried was even anodized, just bare alloy.

Ken
 
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Ken,

I agree with you, and many others have made the same experience. Phil Pearson finally switched to a steel sprocket for his Goldie / Suzuki clutch adaption. The NEB clutch also employs an alloy basket and a steel sprocket bolted on. I was thinking in the same direction, progressing the design even further by using a sprocket design similar to the "ring" type now offered for the Mk3 rear wheel carrier. The inner diameter sprocket support would be part of the basket, saving even more weight. I will do some modelling shortly to exploit the possibilities.

-Knut
 

KiwiNeill

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You could get close to a 1500g -3.3lb weight savings from an alloy clutch basket as the steel one is 1962g and an hard anodised, all alloy copy would be around 670g.
I prefer the durability of the O.E. steel clutch basket however and maybe things like a hard anodised rivetted backplate replacing the steel one would help get the total weight reduction of a duplex Barnett setup closer to 4lb and within 1- 1.5lb of a typical belt drive weight going by the 30mm Old Brits kit.
That,s probably as far as I,ll go with it, just bolt it all up and walk away, got a hydraulic clutch setup to do next.
 
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i have seen that before . good luck finding one and it would be a fair amount of work to make one, to truly do it right you would also need to angle the clutch splines to match the hub angle. with what i have it is still a very light pull on the clutch with NO slipping so i am happy with it as is.

There is a method of modifying Norton clutches called the heinz-kegler servo clutch mod here-look at p12;

https://www.accessnorton.com/Norton...ne-of-these-amc-gearbox-clutch-centers.10997/
 

lcrken

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More progress. I got some thinner plates from Old Britts and narrowed them to match the ones I have. I ended up with two .065" thick plates and two .075" plates. That put the top of the clutch pack almost exactly flush with the end of the splined center hub. This picture shows it pretty well.

Clutch Pach Height 1200.jpg


This is a shot of the completely assembled primary drive, finally!

Open Primary 1 1200.jpg


And this is how it looks with the CF cover on. The patterns on the cover are mostly anomalies from the camera flash. The appearance is much more uniform than it looks here.

CF Cover 2 1200.jpg


I've also finished the modified seat pan, and have a new cover to install. I've refurbed a pair of period AP Lockheed racing master cylinders, and am in the process of making up new hoses. The clutch is finished, but I'm waiting to sort the headlight mounts before finishing the brake lines, just to make sure there are no interference issues. This is a shot of the bike as it is now. I've stolen the carbs for the landspeed bike, so I'll have to either put them back, or fit something else.

Left Front 1200.jpg


Ken
 
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Awesome Ken, Just one thing... I looked at this picture below and there's no exposed threads on the shaft end to use a dyno dave style clutch rod seal. Seeing as how you are going dry primary case/belt drive, are you considering milling down the nut in the picture to fit a clutch rod seal ?

 

lcrken

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primary cover is gorgeous!
Thanks, Jon. I'm happy with it. It took me three tries, and there was a real temptation to do a fourth one and get it absolutely perfect, but I managed to resist:).

Ken
 

lcrken

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Awesome Ken, Just one thing... I looked at this picture below and there's no exposed threads on the shaft end to use a dyno dave style clutch rod seal. Seeing as how you are going dry primary case/belt drive, are you considering milling down the nut in the picture to fit a clutch rod seal ?
I wasn't planning to. I haven't really had any problems with leakage on the other belt drives I've used, so I'm not expecting any with this one. If I do have a problem with it, I have one of Dave's seals on the shelf, and I'll see about fitting it. FWIW, I do use a slightly larger diameter clutch push rod than stock, so there's not as much clearance for oil to migrate through.

Ken
 

lcrken

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Latest update. When I finally got some time away from the other projects to work on this one again, I discovered that I couldn't come up with muffler mount system anything like the original, primarily because the wider swinging arm hits the fasteners at the back of the Z-plate. If I space the Z-plates out further, there's no room for the muffler mount hardware between plates and mufflers. I tried to come up with something even remotely like the original mounts, but couldn't. In the end, I decided to use Production Racer style mounts, but modify them to take the stock style footpeg mounts instead of the PR rearsets. Lots of work with the rotary table on the mill, but the end result came out pretty good.

Z Plate 1200.jpg


Now that the exhaust system is done, I can work on getting a rear brake mechanism. I'm planning to use the small Aprilia master cylinder lying on the lift. The bike will go back to the older Commando configuration, with brake on the left and shift on the right. I've given up on designing a mechanical linkage crossover system. Way too complicated, with lots of levers and links. And the cable arrangement I worked out was just plain ugly. What I really need is a hydraulic system, with a couple of very small two-way cylinders. I haven't found anything that looks like it will work, so far. If I'm careful with the design of the foot levers, I can leave the option open of later switching to left shift.

Ken
 

lcrken

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Finally got the rear brake system finished. Now I just need to do a shift linkage on the other side. All the fabricated bits are titanium, except for the aluminum adjustable link. Been working on the front fender and electrical system too, but nothing worth showing yet.

Rear Brake Lever 1200.jpg


Ken
 
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Finally got the rear brake system finished. Now I just need to do a shift linkage on the other side. All the fabricated bits are titanium, except for the aluminum adjustable link. Been working on the front fender and electrical system too, but nothing worth showing yet.

View attachment 16478

Ken
Can you tell me which model Ohlins and the spring rates your using? NICE WORK!!
 
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