The Jura Big Fifty build, evolution, repair and a-ha moments

So I said howdy, now's when I share the good stuff (and the bad stuff too).

In 2016 I built the Jura Big Fifty, using an Electra Cruiser 1 and a Bikeberry 49cc 4-stroke kit. This is what it looked like right out of the barn:

And of course there were problems. First I couldn't get the coaster brake to work. Felt like it was slipping. So in spite of it being brand new, I rebuilt and adjusted it. Got real good at rebuilding and adjusting coaster brakes. Still no go. Then I decided that the coaster just wasn't up to the task of stopping 300 pounds of bike and rider, even with the Sturmey front drum helping out, and ditched it. Got a new rear hub from Bikeberry/BBR that uses a thread-on sprocket and comes with a thread-on band brake.

The sprocket and hub was a wonderful upgrade. The Bandbrake was worthless. Worse than the broken coaster brake. Then the transmission input shaft broke and I had to pedal home. That's when I had the first a-ha moment. I had slip in the pedals while pedaling forward, too! Turns out the problem wasn't in the coaster brake, but in the wide crankset. The sprocket is pressed onto the shaft, and none too tightly. Hit it with the welder (just a couple tacks) and that problem was solved. But now I was stuck with this useless bandbrake, or so I thought.

Finally did something about it when I found a thread-on disc brake adapter. Bought that, a Tektro mechanical brake, made a mounting bracket and welded it to the chainstay. It barely misses the sprocket, and wouldn't miss the chain if I tried to mount it elsewhere. Sorry it's a little hard to see.


I'm sure you noticed the chain's off. More on that in a moment.

The brake cable was way too long, and I almost cut it but then had another a-ha moment. The extra cable goes into a piece of 3/16 brakeline (or a noodle if you want to use bicycle terms) and up under the rear rack, where it attaches to an ATV brake light switch. So now I have a real brake light (a GOOD one, that uses a real 1157 bulb, not LED's). Picked up the switch and lamp on Amazon.

So the wheel's not orange anymore, what's up with that? I changed the front to a 24 to match the rear, and the ride is a hell of a lot better now. And since the new rim was black (Odyssey Hazard Lite, way overkill but a really nice rim) I changed the rear to black as well. Looks better to my eye. Re-used the Sturmey-Archer drum in the new wheel.


Tires are Duro Beach Bum 24x3, with the decals buzzed off. Want to know what really burns me about these tires? The sidewall molding doesn't say Beach Bum, it says EACH BUM. Really, Duro, really? Other than that I really like 'em. A soft ride and nice feel overall.

With more rubber on the road and really good brakes now, I can stop from 25 mph in about 40 feet. Good thing I put a brake light on there.

So guess what happened yesterday?


Yeah, the damn input shaft sheared AGAIN, in the same place, My armchair analysis tells me this is probably machined from the cheapest Oriental bar stock they could find, and there's a nice stress riser right where it sheared off, since the other one broke in exactly the same place. My thoughts yesterday were to get a new one made by a machine shop, out of decent steel this time, and with a radius to eliminate the stress riser. But you'd still be pushing 2 HP through a tiny shaft. Might get away with that if you made it from titanium, but I'm not confident in that. So I'm ditching the 5G gearbox for a Grubee belt drive, which should arrive in a week or so.

One last pic, the bike as it sits today:


In this pic you can see the battery that runs the lights, the brace for the engine to the top tube, and the PMS (Puke Management System). What's the PMS all about? Well, the HuaSheng crapped the bed after about 20 miles of riding. It had so much blow-by that oil filled the chamber above the crankcase and got pushed up to the air filter. It would leave a puddle wherever it went. This engine isn't a HS, it came from a friend who gave up on it. It's another Honda clone. The only identification I can see is a pad that says BRAND. It runs a lot better than the HS ever did. So the PMS isn't needed (yet). It connects to the engine's breather outlet and separates out the oil from the air vented to the atmosphere. So far all it's caught is water vapor.

Stuff you can't see: A handlebar mounted light switch and key switch, wires routed thru the handlebars, memory foam grips, gel seat, lots of good stuff that makes the bike a real joy when it's actually running.
Fun with Photoshop:


Been thinking about a bigger tank, but I think I'm over it. The smallest one I can find is this one from Lowbrow Customs, 1.8 gal mid-tunnel Peanut tank. Between the price and the fact (or opinion) that it looks too big, I'm gonna stick with the China Girl. Too bad, I really like the shape, but it throws all the bike's proportions off.
If you could get it down and forward more it wouldn't be so big looking. But then you would have to cut and weld deeper tunnel, just a thought ............Curt
Down isn't a problem, they make the same tank with a deep tunnel. But forward is out of the question. The tank mounts to the frame with a tab at the front & rear. Cut off the front tab and it's flopping around (unless I welded some studs on the bottom). And it'd still be too big.

The only thing I don't like about the China Girl is that seam around the middle. Tunnel could be a little deeper, too. For the price of 'em I might just cut one up over the winter, see if I can make it look decent.
Yes my son did that and welded the seam, and put a tunnel in it, it was a slow go as thin metal but got it...........Curt
More evolution:


Last time I took a ride I got a racing stripe up the back of my shirt, so I embiggened the rear fender, using the bit that I cut off the front. Since the seam is right under the taillight bracket it doesn't show unless you look for it. Added a bit of DOT tape for a reflector. No stripe after today's ride.


This is a temporary measure, a bit of safety wire to keep the brake-light noodle from bending. Now the light comes on as soon as I pull the brake lever. Over the winter this will get brazed on and I can clean up the paintwork.


Also on the last ride, I discovered that I wanted a helmet visor (the helmet is part of the bike, right? Sure it is). So I bought one. Riveted some snaps to the helmet; they don't protrude much into the padding. If I ever end up up needing every mm of the padding, I'm going to the hospital anyway so they might as well stitch up my forehead. And I added some edging. Around the edge. I wear the Red Baron goggles without irony, since they fit over my glasses. No sun on today's ride so the visor didn't get a true test but I had fun anyway, and that's all that counts.

With 175 miles on the bike this year I'm going to put the jinx on it and pronounce it reliable. No breakdowns or failures of any kind since the Grubee went on. Last year I racked up a whopping 1.6 miles (with one transmission failure) because I couldn't trust it, and that's not only no fun but completely pointless. Ever pedal a 90-pound bike with a low seat? It ain't no fun.
Time to change things up a little:


Adding a springer fork, with a few changes and tweaks. One crucial tweak is that since the Electra has a really long neck, the geometry is all out of whack. So I'm making the spring rods longer:


Steel tubing standoffs under the springs bring them up to height. Threaded couplers and some allthread bring the rods up to length. One thing I remember about springers from back in the day is the WHACK sound you get on rebound. So I'm taking a page from the Harley-Davidson playbook and adding rebound springs up top. That's why the rods are so long. I had to open up the ends of the springs with a die grinder to get the couplers in, and tapered the tops of the couplers to smooth things out as they travel.

The springer came from ebay, with no name or packaging, so who knows where it really came from. It's supposed to be chrome-moly but I have doubts. Maybe tis, maybe tisn't.

The tire just clears the fork:


Close only counts in horseshoes and hand grenades, right? 4mm on each side. Since there's a bit of taper in the legs, I made sure the tire won't hit at full travel; coils bind before the tire contacts the fork. I'll probably add a shorty fender.
So here's something I ain't too happy with:


Dropout faces the front, and there's really nothing in the way of a positive stop to keep the wheel in place. I suppose the T-shaped opening is meant to hold the axle in place, but it don't. So I improvised:


Welded some 1/8 flat stock to 3/8 washers to make wheel locks. They fit into the dropout slots and hold the wheel up in that top slot. As long as the nuts are in place (they can back off up to 1/8 inch and still be safe) everything's locked tight. And if the axle is locked down like this, it can't wiggle around and let the tire hit the fork. Hooray safety!


Like so. I love it when a plan comes together.
Busy, busy busy...


My rebound springs arrived and I couldn't wait to try 'em out. Everything's rubber mounted so there's no metal-on-metal contact to make noise. The springs themselves I found on Amazon, had to buy 10 to get two, so I have plenty of spares. The rubber hose inside just keeps them centered.

This thing just glides over bumps now. I think I'm in love.


Made a new brake arm, a little awkward but it works and it's super strong. The cable wasn't long enough so I picked up a rear brake cable, which is way too long. I'll hack it down once I come up with a barrel nut.


If this fender mount works in the long term, I'm a genius. If it balls itself up and wrecks me I'm a moron. Time will tell. The mount itself is leftover threaded rod, some nuts and washers around a short length of rubber hose (you can see it thru the hole in the fork). Tighten the nuts, the hose expands and grips the inside of the head tube. The fender itself is 6 inches shorter now, and doesn't vibrate. Rubber mounts dampen any vibration that it does do. I'm pretty confident in it.
Well, crap.

Today I learned that I really don't like this springer fork. It's wonderful over bumps, but really really floaty feeling when cornering. Does not inspire confidence, and there's no point in building a bike you don't trust. So back to the original fork, Rides like a damn farm wagon (amazing how fast you can get used to the good ride) but corners just like it did before I started monkeying with it.

Bonus: All the pivot points (and their attendant potential for failure) are gone. Strong and simple=trustworthy. I'll put the springer on my pedal bike since I don't ride that fast enough for it to matter.