75 Mark III refurb/mod project

grandpaul · Mar 5, 2010

Got all the rising rate linkage bits & bobs in order, installed the swingarm pivot pin with oil-soaked wixks and replaced the welsh plugs,
installed the rear isolastic gaiters, then re-installed the rear end. Pulled the freshly overhauled (Old Brits) tranny out of it's plastic bag
and popped it into place, nipping it up with it's spacer washer-

One of the easier go-rounds I've had dropping a Commando engin into the chassis; installed the front "shorty" crankcase bolt, front isolastic
mount and bottom thin case stud, then hustled it straight into position, FIRST ATTEMPT. All the bolts lined right up with no fuss, nipped it all up-

That's all for this weekend; I'm heading out to the local MX races to run the hospitality tent with coffee, tea, lemonade & ice water,
plus I'll be doing double duty as pit mechanic for anyone needing assistance.

grandpaul · Mar 8, 2010

Ready to install the head, strips of cloth stuffed in the pushrod tunnels to keep them from dropping out when the head is being placed in position-

Head installed and torqued down-

Replaced inner primary seals-

Installed primary system-

grandpaul · Mar 8, 2010

The shifter shaft seal was a BUGGER to get out-

Primary all nipped up & starter installed-

Installed the kickstarter and cycled the engine through a couple of times, slowly; all good-

Looking more and more like a bike-

swooshdave · Mar 8, 2010

Does the Z Plate bolt up to the rear iso? At what point do you put that one? Is there a reason to wait?

grandpaul · Mar 9, 2010

Yes, the rear iso mount bolt runs through the Z-plates.

They are going on soon enough!

grandpaul · Mar 9, 2010

Carbs were cleaner than a whistle inside, so I just wiped them down and took 0000 steel wool to the outside of the bowls to knock the "tickle" stains off 'em-

Carbs and new stainless rocker feed line installed-

Oil tank is at the radiator shop getting this mess cleaned up and properly repaired-

grandpaul · Mar 10, 2010

Just a progress mock-up to see where it's headed...

Danno · Mar 10, 2010

Where are you getting all the inverted front end setups? Are they very expensive and how much must be done to adapt to the Commando frame?

grandpaul · Mar 10, 2010

The front ends come from a local all-brands shop that deals in used bikes and parts; his family was the Yamaha dealer since the VERY early days.

They are about the same price as buying a used Commando front end and overhauling it. It's the custom hubs, bearings, lacing, discs & spacers that add up.

The steering geometry is much tighter, while the parking lot turning radius is like a modern Triumph triple or a GoldWing.

All you need to do is replace or turn down the yoke stem to 1" diameter to slip into the Norton bearings, then trim the length to suit the "yoke sandwich" in the Norton neck.

swooshdave · Mar 13, 2010

grandpaul said:
One of the easier go-rounds I've had dropping a Commando engin into the chassis; installed the front "shorty" crankcase bolt, front isolastic
mount and bottom thin case stud, then hustled it straight into position, FIRST ATTEMPT. All the bolts lined right up with no fuss, nipped it all up-

So, front iso on the engine, then slip in into the frame and install the back three bolts?

Bill G · Mar 14, 2010

Nice!
How are you planning to mount the battery?
Bill G

grandpaul · Mar 14, 2010

Yes, on the engine install.

Haven't quite figured out the best spot for an e-start capable battery yet, but I'm working on it.

It will probably involve the left sidecover area.

grandpaul · Mar 18, 2010

Oil tank repaired and touched up-

Installed: wiring harness, coils, Boyer box, stator & rotor, rectifier, keyswitch, clutch cable, seat, oil lines, oil filter, and header clamps.
Removed top yoke, pulled clip-ons, replaced yoke and installed clip-ons above to provide better tank clearance at steering lock.
This is the only concern right now-

Being that it's spill-proof / sealed, if I remove the tool tray in the sidecover, I can fab up a tray for it there.

Adjusted the valves, set the crank at 28 BTDC-

Set up the ignition stator at mid-range, and nipped up the rotor with the dot showing in the window-

grandpaul · Mar 18, 2010

Topped off the oil tank, primary & tranny, then poured 1/4 cup of oil into each of the rocker inspection openings.

Installed the fuse, double-checked for spark at the plugs and made sure the kill switch worked then replaced the plugs,
dumped a gallon of gas into the tank, opened the taps & tickled the carbs till they just dribbled.

Turned on the key and kicked it smartly, it almost caught. Tickled the carbs again, kicked it again and it fired to life at a high idle.
Checking for oil return, it came up immediately-

Played with the idle adjustment after pulling the chokes up, it's stumbling just a tad off-idle,
but that's because I haven't installed the air filters yet.
Still a way to go before test-riding, but it's running! (108 shop hours)

grandpaul · Mar 19, 2010

Today was the push to get the preliminary road test. Had to have brakes before thinking about taking it out, so the rear brake was the first step-

There was some pretty nasty crud in the reservoir-

Removing the reservoir resulted in a layer deeper than the fat o-ring at the bottom!

grandpaul · Mar 19, 2010

The plunger body was totally clogged with an amalgam of brake fluid, moisture & debris-

Another bunch of grunt removed-

The inner plunger valve was half plugged, leaving only one of the three orifices clear-

grandpaul · Mar 19, 2010

The main cylinder body is not too bad off with a bit of etching, it will seal just fine with the new o-ring-

Fairly clean external plunger section-

Much better...

grandpaul · Mar 19, 2010

Used a hand pump and got a nice solid pedal PDQ-

This wasn't critical to a test ride, but I wanted to nip up some of the loose hanging stuff; rear fender was pretty sorry-

I had to trim a couple of inches off the bottom to clear the upper monoshock arm, then mounted it up. After that it was a forgone conclusion that the starter solenoid & rectifier had to find new homes-

grandpaul · Mar 19, 2010

Initial test ride with rear brakes only showed that the front suspension is set too stiff; rear feels great. The bike DEFINITELY has guts! The sound of the header is very throaty and "vintage sports car" sounding. No suprises.

The primary side gets it's first reasonable photo. The chainguard needed a 2" notch trimmed off the front to clear the swingarm, not a bad compromise-

Tomorrow I'll get the rear brakes done on the Silver bike, and both sets of front brakes done (if I can get a custom hose made to go from the Norton master cylinder to a modern banjo fit manifold).

grandpaul · Mar 19, 2010

Went ahead and put in some more shop time after dinner, got the head & tail lights installed; still need to wire up the tail light.

I still need to get some more flat stock and make a pair of upper brackets for the headlight to triangulate both sides.

75 Mark III refurb/mod project

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