00137 Honda 1980 C70 Passport / Cub

Phil's got my old Aermacchi, but I'm currently tuning his Honda Passport C70. Aka the Cub, it is the most common motorbike on the planet. This one was not idling at low revs, despite having the carb cleaned. On inspection, the bamboo points armature that is actuated by the cam on the flywheel had worn down to such a degree as to not open the points. This was resolved by simply adjusting the points. The oil centrifuge was de-sludged, and the gaskets replaced. Battery, though it holds a charge, probably doesn't have much life left to it. I'd have liked to take a look at the tappets, but the damn covers are seized to point where removing them would destroy the covers and possibly the threads on the head, so that's just not gonna happen. 

Now you see the engine.

Now you don't.

Sludge...wish I could get my guitar to sound like that looks.

 Pretty clean.

 Oil pump is fine.

 clean enough to pour oil on.

3rd world manufacturing

 Screwed into the case half...pretty ingenious design, so des ne?

On to the points! 

Points aren't moving. That there's your problem.

 Melted and corroded and generally non-conductive around the ignition and the electric starter circuits.

 Many hours later: 

Ahmed's Whizzer Rebuild

Ahmed had wrecked the shit out of his 60cc whizzer. I replaced the front end, rebuilt the front hub with a solid axle instead of quick release (!),  re-attached the clutch cam housing and added a lever with the correct amount of cable pull so the clutch would work, rebuilt the axles, tuned the carb, fixed the kill switch, replaced the broken throttle with an old Suzuki control, rebuilt the back hub so the brakes would work and the chain ring wouldn't rub on the brake arm, added a front brake (!),  trued the wheels and generally tightened everything to spec w/loctite. My final verdict after the test: whizzers are fun but totally dangerous. I gave Ahmed an extra helmet and told him he wasn't allowed to crash anymore.

Cute!

 

sachs g3 performance clutch tuning

Stock Vs. Performance

Installation tutorial

So the stiffy springs went into the clutch part number 20 without too much knuckledragging and yep, not only do they work, they work better than stock, 'cause they're 15% stiffer. Testbed is my "problem child" sachs g3 w/ 505 /1A engine 48mm athena reed valve, 19mm Mikuni from a Kawasaki KH125 main jet 80 pilot 45 needle one notch from lowest, ghetto hacked biturbo pipe, stock gearing 43 mph top speed @ ~10K RPM. Frankly, it's ghetto as hell, and I know for a fact that I need new rings, but I digress. The clutch spline (No. 18) has been drilled and tapped for a set screw (w/ red loctite), plus two red loctited axle nuts tightened against each other on the end of the crankshaft (No. 12). So far, no problems with slip there. I have no tach so I'm guesstimating, but my guesstimate is engagement occurs ~1k, and the engine spins up enough power to make the clutch plates slip under extreme loads, but that's another problem most likely related to not having a shim in there. I'd say its a ~20% increase on stock takeoff engagement of around ~800 rpm. The bike takes off up grades that were previously impossible. As always, there is room for improvement. I look forward to hearing what people running superclutches or milled clutch plates have to say about their experience running these springs. If you're one of these folks that would like to replicate this experiment in yr own lab and report back with the lowdown, hit up OB1 to hook it up. Pix or it didn't happen:

Sachs G3

lizzy on her g3

80cc 45mm reed valve athena kit on a 505/1a bottom end.

19 mm mikuni vm? i think some old clone 85 jet drilled out to somethin' that works, problably around 90 but who knows for real?

the pipe's on the wrong side 'cause of the header! biturbo chamber hangin' on there.

rear wheel geared to 43. puch mags, 3.0 gazelles.

gets to 40 pretty fast. tops out at 43. revs to all jesus even though it's restricted on purpose to help the bottom end and especially the clutch not explode with the bendy air intake. the exhaust header is skinny 19mm? i'm pretty sure. it's kind of flattened where i contoured it so the chamber fits on the bike.

thanks to josh at TBS for hookin' it up.

zowie look at those transfers

replaced broken circlip, regasketed the case halves. case matched!

clutch nut slippage problem solved by using two axle nuts. i loctited them, too. a hundred miles later so far so good.