"Test Mule" '74 850 Monoshock build

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This bike will gain HP from the lumpy cam it's getting, with a bit of porting and 32mm Amals over the 30s that it had.

I'm trying to come up with an analysis of the modifications and how they'll affect overall handling:

1. Monoshock rear end weighs slightly more than the standard setup, but is far stiffer
2. The shock is fully adjustable in compression, rebound & pre-loading versus preload only on the originals
3. The rear shock compression RATE is adjustable (rising rate linkage can be set 3 ways)
4. Front forks weigh about the same, but a greater percentage of the weight is SPRUNG versus UN-sprung
5. Front end is much more stable as far as bracing / twist potential with those massive triple clamps
6. Front brakes are about 10X more powerful than the originals

Overall, it's a pretty clear "plus", as the total weight will be slightly LESS than the original setup, with everything else being better (performance-wise).

Still, there is no getting around the fact that it takes some doing to overcome the deficiencies of the isolastic setup as relate to the overall handling in extreme circumstances. Rigid top & front steadies will help minimize, but not negate, the inherent flex.
 
Received the cam and followers back from Megacycle. Does anyone recognize the geometry? They couldn't pinpoint it.

"Test Mule" '74 850 Monoshock build


Also got in the floating rotors, just need to send off the hub to have it copied for the client's build.

"Test Mule" '74 850 Monoshock build
 
Cylinders nicely honed, and when I went to mask them for painting, I realized somebody skimmed the heck out of the deck. I guess this will be a bit higher compression than stock...

"Test Mule" '74 850 Monoshock build


Bearings dropped right in after setting the cases in the oven at 300 for 12 minutes, zero effort whatsoever.

"Test Mule" '74 850 Monoshock build


Presto!

"Test Mule" '74 850 Monoshock build


That makes all three Norton bottom ends closed up and now waiting on Cad plated hardware to start installing the engines and assembling the bikes.
 
grandpaul said:
Cylinders nicely honed, and when I went to mask them for painting, I realized somebody skimmed the heck out of the deck. I guess this will be a bit higher compression than stock...
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Thick base gasket? Or just appreciate the extra juice?
 
Since it's running a "warm" cam, may as well enjoy the added compression as a package deal. Afer all, it's not being built to do runs to the grocery store...
 
grandpaul said:
Since it's running a "warm" cam, may as well enjoy the added compression as a package deal. Afer all, it's not being built to do runs to the grocery store...
Click to expand...

Depends on where the grocery store is. :mrgreen:
 
FINALLY got in the Cad plated bits today, took over 2 hours to sort it all out (3-1/2 bikes worth of bits, plus a bunch of spares)...

"Test Mule" '74 850 Monoshock build


Engine assembly and some of the basic chassis assembly can now start.
 
Tranny looked clean enough, but I figured I'd double check the bushings and gear teeth...

"Test Mule" '74 850 Monoshock build


Sure enough, the insides were in good shape with just a bit of trash in the bottom of the case-

"Test Mule" '74 850 Monoshock build


Everything cleaned up okay, tbut the bottom of the case is stained. No biggie-

"Test Mule" '74 850 Monoshock build
 
Drive sprocket is a 20 tooth unit, seals & bearings were perfect (probably overhauled when the engine went .020 over)-

"Test Mule" '74 850 Monoshock build


Dropped in the lower lump as well-

"Test Mule" '74 850 Monoshock build
 
grandpaul said:
Drive sprocket is a 20 tooth unit, seals & bearings were perfect (probably overhauled when the engine went .020 over)-

Dropped in the lower lump as well-
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So is that the easiest way to install the engine? Swingarm and cradle all assembled and the front mount and then drop the engine in?
 
I do it three different ways. This is easy if you have a lift to raise the bike for installing the top end (I've got two lifts now).

I don't like fighting the frame and lifting the ENTIRE engine (oooh my aching back).
 
grandpaul said:
I do it three different ways. This is easy if you have a lift to raise the bike for installing the top end (I've got two lifts now).

I don't like fighting the frame and lifting the ENTIRE engine (oooh my aching back).
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I do plan on getting an "volunteer" to hoist the engine in. And no, not the wife...
 
You now have a good stiff front end, a suppossedly superior rear end, but the front and rear are still only bolted together by 1/2 dozen used condoms, why not cut the swing arm out of the engine cradle and mount it to the frame, chain tension would vary, but , it would be a small price to pay to get the best out of a reasonably designed frame.Side benifit is the engine cradle could be a lot lighter.This is just an :idea: :idea: running around in my narrow little mind, and perhaps some one could tell me why it won,t work :?:
 
splatt said:
...why not cut the swing arm out of the engine cradle and mount it to the frame? chain tension would vary, but , it would be a small price to pay to get the best out of a reasonably designed frame.Side benifit is the engine cradle could be a lot lighter.
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Sounds like a worthwhile venture; have at it!

That discussion went on not that long ago, and touched on several areas. It really does sound like something someone here would have tried by now...
 
ludwig said:
GP , I admire your enthousiasm and energy , but your design is flaud .
'Monoshock' means one shock/ spring , but you have a few more : those soft rubbers we call isos .
the reaction force of your suspension strut will be completely taken up by the isos , and push the rear wheel back as far as the buffers in the isos will allow.
It will also influence rear wheel travel beyond control .
About the front fork : what happened with the 1.5 deg. designed into the 850 tripple tree ?
did you calculate rake , trail , squat , anti squat ? ...
IMO , you'll have a lot of work to make it handle nearly as well as a STD Commando .
It will take a brave man to ride this one to the 'grocery store' .
( take a look at Jim Schmit's frame to see how it's done )
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Believe it or not, I have done the math! The 18" wheels and different tire profiles front to back will bring the geometry into reasonably good form. These are not race bikes, otherwise I would rather be custom building frames including the above mentioned swingarm relocation to the frame instead of the iso chassis.

As far as "beyond control", not so. The handling will not be much different from a standard Commando, other than a wider turning radius at slow speeds.

If I had more play money, I'd LOVE to have one of Jim's frames.

...and a Maney engine...

...and...

For what it's worth, my '75 monoshock / inverted fork 850 handles quite nicely in everyday riding. I very much want to get it out on a nearby race track, but have to wait until March to seriously flog it and see how it responds.

Furthermore, the beauty of this entire "custom" build is that the original bits slip right back onto the bike, totally unaffected (except a spare new swingarm, of course).
 
Mounting the swingarm directly to the frame would be a disaster. Look at Featherbed to see what it takes to hold it, the frame is in no way up to the job. The problem is that the shock is practically horizontal, it introduces the iso's into the suspension. The stock setup has always done this to a certain extent due to the laid down shocks but as it is your iso's are going to see hundreds of pounds of force and deform accordingly. You'll miss dampening and control of the rear wheel.
 
I understand that these are valid points, and I'm sure there will be life-cycle cost issues to be dealt with (replacing iso rubbers more frequently). Hopefully, they will be relatively benign and offset with the far superior fully adjustable suspension unit (compression, rebound & pre-load adjustability).
 
Ludwig - now I am even more keen to get the bike out on the track and really put it through it's paces.

I do not disbelieve you, just that my blue bike has exhibbited no ill effects whatsoever in this configuration, in standard riding conditions. i really MUST go to the next level in a safe environment to get a better picture of what is going on.

I will go back to my notes and get the rake and trail figures, they vary slightly from my CAD drawings to the actual bike, and I don't have precision equipment to measure them in-situ. This must be what the new guy was referring to as "shoddy"; I'll accept the criticism in technical form, but reserve the right to dispute it in actuality!
 
bpatton said:
Mounting the swingarm directly to the frame would be a disaster
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Enlighten me, as I look at it the rear iso mount could be refabricated and a modified swing arm could be mounted in exactly the same place.The pivot tube bolted between the frame tubes would also stiffen it up the frame.
 
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