Bridgestone 100(s)

Way on back before I was obsessed with mopeds, my brother found a small pressed-frame motorcycle in an antique shop in Tomah wisconsin. I think it was the ungodly sum of 200 or 300 bucks, which we had saved up from mowing lawns at the time, but our parents forbade us from buying it. Instead of getting the damn thing, getting mad, and getting bored with 2 wheel vehicles, we became obsessed with it and I'm writing you today. We spent months looking up everything we could on it, the internet was pretty small back then so there wasn't much, but we found out that Bridgestone, the tire company, made motorcycles for awhile. Seemed kinda funny at the time, like they were probably a 'also-ran' sort of thing, with no parts availability and crummy quality.

Through my next few years of owning, fixing and generally being around all kinds of vintage 2 stroke machinery I came across a few other Bridgestones. They didn't impress me much, but the few I saw looked like they were comparable to any yamaha of the time, and pretty simple with none of the whingdings common to, say, hondas. Nice simple bikes.

I was talking to a guy about a 175 GT, high pipes and the works, pretty cool bike... but it was pretty beat down and he wouldn't go below $300,  I was at about $100 because of all the parts needed, and the whole 2 cylinder thing kinda scared me with syncing carbs, and twice as many ignition/carb parts to buy.

Finally a few months ago a post went up on Craigslist with a 100 G/P in boxes. It was one of the tube frame- road race style ones, probably one of the best bikes they ever made, and the guy said the motor was good, just needed some reassembly. I probably shouldn't have even gone to look at it, but I did and when I saw the bare tube frame sitting there, I fell in love. I knew it was a bad idea, but that frame was just so beautiful, very much like a 60's rickman race frame. Plus, it was dirt simple and everything appeared to be there.

I started doing some digging on the internet and found that not only was Bridgestone a premium motorcycle at the time, they produced some of the 60's fastest 50cc twins, borrowed some of europe's best technology at the time and produced a hand crafted bike much better than the yammies and suzukis in their class. They were considerably more expensive and boasted more power with rotary valves, chrome/aluminum cylinders, aggressive porting, and very well made chassis.

It ended up turning into a huge project as these things always do, plus I ended up with the TMX off road version, which is in much better shape and totally complete. Here is a quick rundown on how that all happened.

This is roughly the condition she came home in. This picture was taken after a few hours of sorting out parts, cleaning some things up, putting things back together the right way. The forks were a godawful mess, the springs were jammed between the triple trees and all the little hardware that places the springs and some of the neck bearing hardware was jammed in and around the springs in a most illogical manner.

By this point I've re-assembled the fork tube parts into the right order, and found enough used moped wheel bearings to stuff the neck full of loose bearings and grease. Somehow the rubbers on this bike are all in pretty good shape, including the fork boots, which is cool because the fork seals are intact and there is very little rust on the sliding part of the forks.

First I bored out the handle bar clamps from the weird diameter they were, some tiny proprietary junk, to a standard 7/8" diameter handle bar. The controls were pretty messed up and would probably cost more to get the few missing parts than completely replace, and the old bars were a little bent anyhow.

Apparently, the poor girl was found a few years ago in a barn in northern WI. Two or 3 consecutive owners attempted shoddy 'restorations' but luckily they were too lazy or incompetent to mess things up very badly. A long time ago tank and tins were painted in a ghastly blue metallic paint, someone took the time to partially clean these up, but then someone else painted all the silver tins (fork ears, headlights, etc) with flat black, and very poorly.

The frame has been spraypainted black, but there is a lot of dirt underneath, and you can tell things like the rear wheel were never removed.

Its too bad, because thats the kind of work I really hate doing, but oh well. After figuring out loosely what was missing I put together a box of crap to sandblast and return to the OG silver paint.I made an executive decision early on to get this running and riding in imperfect shape, to have fun with it and not nit-pick fit and finish.

The headlight was busted so that had to get welded back together.

Welding rust to dirt, not the best

Oh well, nobody will see it.

Good enough for a driver.

One of the studs on the fork tube was torn out, so i machined a new one and TIG welded it in place.

 Painted the fork lowers with the same silver paint.

Some random little crap had to get made for the motor, this pin is part of the clutch throwout mechanisim. It was missing from long ago

After a couple months of plugging away at this, a buddy said he had another Bridgestone 100. I stopped by his shop and I had to have it. Its the matching TMX and in much nicer shape than the G/P.

Carlos is a friend of mine and an excellent motorcycle mechanic. He got the bike running and rode it around a bit, when he went to do the performance mods to the rotary valve, he found that the kickstarter engagement cog on the clutch was smoked. Apparently this is a very common problem on these bikes so he wanted out of the project. Another Bridgestone in a box, I'm obviously not right in the head.

I took the motors in to the machine shop to use air tools to remove the nut holding the clutches on. First I disassembled the gold bike engine, woof. This thing was beat pretty hard. Right away I noticed the piston and jug which were pretty well shot as advertised. Someone put a hi-flow filter on this thing, and the rubber joint in the exhaust was completely shot. It was probably running lean as hell until someone seized the ever loving crap out of it.

Carlos told me about that, and did a pretty good job of cleaning up the cylinder, but it is still scored all to hell. The GP bike has a bad cylinder too, for a slightly different reason. The chrome is chipping off in a little spot next to the exhaust port.

Took the clutch apart, this thing has been hammered. Someone wore out the pads really bad, then they welded in a shim to hobble it along, then they cut 2 new pads with what looks like a jig saw.

 And finally here is the offending cog part, sticking up there. You can see here how it is supposed to look.
 HA, the chunks were just sitting there. These cogs go from the kickstarter mechanisim to spin the clutch housing . They are machined in the cast iron gear with no fillets on the bottom, and i'm sure they took a lot of abuse with kids jumping on kickstarters and general beating around that these bikes take.

 I knew the ones in the Gold bike motor were shot, so I took the blue bike motor apart and figured I'd swap the whole clutch out of the blue bike. I could tell the pads and such were all in much better shape. Disassembled the second motor and guess what! Yep the cogs were smashed out of that one too.. Damn!

 Two lonely Bridgestone motors, both with bad top ends and bad clutches! Depressing!

The master tool and die maker that owns the shop I work at said 'why not just machine a bushing and fix it' I had originally thought i might try to save the second motor by doing that, but now I had no choice. We talked a bit about how to make it, and he offered to let me use some cold rolled steel that should be crazy tough compared to cast iron.

Started by turning the slug down to fit.

 Then machined off the old cog to get a square surface.
 Which I indicated and bored out to 1_1/16 to fit the bushing

Bushing fit on the shaft with .0015 tolerance

Bushing press fit into gear

Bushing cogs machined out- this time with a slightly radiused 5/16 end mill to give it more strength
Both gears fixed
Shaft was a little chewed up from chunks of metal rolling around in there
Cleaned up the shaft and re-installed the clutch drum
Gears meshing-  a perfect fit.
The engine fully reassembled.
So in order to get this running for the frozen snot ride, and general romping about, I took the clean cylinder with chrome chipping off from the blue bike engine and put it on the clean (running) crankcase and transmission from the gold engine. The good clutch from the blue engine went in here too.

Here is the engine set in place, I'm finding out at this point that a lot of oddball hardware is missing. Luckily, in the process of putting the GP together, I've amassed a pretty good stash of fasteners. I've really been meaning to get out to a place with bulk metric fasteners and stock up a huge stash for this sort of thing, instead I rang up another $20 tab at Phule's True Value down the street... d'oh!

A little farther along. The tank had to come off to get at the coil. This required removing the balancing tube which had been kreemed on. Sweet mother of Jesus do I HATE kreem, pretty much the worst idea anyone has ever had in all of motorcycles. More on that later...

The coil wire was broken off near the coil, this painfully common on old motorcycles. The spark plug wire technology back in the day wasn't very good, rubber itself was still pretty primitive compared to the formulations available nowadays, and the Japanese were trying to cut costs by any means necessary. Where Bosch and CEV and others in europe were putting a wood-screw type dingus in the coil for you to jam the spark plug wire into, TEC and the Japs were saving a couple pennies by soldering the wire direct to the coil. The combination of heat, chemical exposure, vibration, and general abuse something sitting a few inches from the cylinder head takes, most of these spark plug wires and boots resemble a tube of tar with a wire inside it. Not very good for screwing into a spark plug boot.

I first figured out this trick when i rebuilt a CB450 sometime back around 2006.... its pretty obvious but if you do it wrong, you will go crazy trying to rule out reasons why your bike wont start. I stripped off the insulation from the spark plug wire in what i felt was the least-kinked place. Then I soldered on a new piece of copper core wire. This stuff is getting harder to find in favor of the graphite core, which obviously will not take soldering. Then I slipped a piece of fuel hose (any sturdy hose will work... i think i used 5/16" ID on this guy) over the joint after liberally applying some RTV silicone. The key being to apply the silicone to fully fill the gap between insulation, and rotate the hose back and forth into place. You dont want any air, moisture, or other nonsense to get in there.

In the end it looks like this:

With a nice long spark plug wire, plenty of room to cut-to-fit and a brand new NGK spark plug boot.
At some point in the 80's, the Jap OEM's really fixed the heck out of this problem... To be honest it probably took about 20 years from 1960 or so until 1980 for them to even realize how big of a pain in the ass the soldered in wires would become, and the Japanese are not known for making things to last forever, as their culture involves a lot of buying new junk and throwing old junk away at an astonishing rate. (Not to say modern-day America is any better) But I digress, the later model high tension coils used on 80's sportbikes are really quite awesome, they have screw-on crimp terminals that allow you to easily replace spark plug wires, and they almost never fail. If you are setting up a 12v DC ignition system, for something like a 70's honda CB... you're much better off going out and finding some later model coils with the new style connections.

By the end of Tuesday night, she was looking pretty complete. It was almost impossible to resist the urge to give her that first kick...I had hooked up the battery and kicked her over with the spark plug out of the head and she snapped a tremendous bright blue spark. The fuel line was plumbed but the oil line wasn't. The air intake plumbing was all set up. I made an executive decision to change the plumbing for fuel and oil a bit. The fuel line typically runs through the carb intake boot, but i had two brand new boots that came with the bike, and adding another hole in them sounded like more potential for air leaks. I ran the fuel in through the old oil hole, which was a perfect fit to the heavy duty Gates (I always use any gates rubber products when I can) 3/16" fuel line, and I drilled a new hole for the oil line. I ended up getting some extra crummy, non braided vaccuum hose for the oil plumbing, so I drilled a small hole in the case and jammed it through with a pretty good interference fit to seal securely.

Let me tell ya a second why I chose the vaccuum hose, first of all there isnt much room under the cover for hoses in general, and using the neoprene non-braid hose allowed me to use a small diameter and the wall thickness is much less. The oil is less chemically active than gasoline (more specifically the ethanol in the gas i'm forced to buy and subsidize with my taxes) so I wasn't as worried about shrinkage, and the two different sized hose barbs on the oil injector/oil tank... no idea why they did this... made it ideal to use a non-braid hose that i could heat up to soften, and shrink-fit onto the hose barbs. In the end it resulted in a very professional look, and the shrink-fit will prevent any air leakage (sucking air into hardened oil injector lines is the end of many injected 2-strokes). I'll add some pictures of the result, It looks pretty good and would definitely be a good project for anyone with a vintage Bridgestone that has hardened oil lines. The line that came off this bike was a ticking time bomb for air leaks.

Wednesday was devoted to making sure everything was perfecto- doing a bit of tuning, cleaning the points, checking the oil injector, making sure all the carb jetting was correct/close... getting the lights all working, etc. I couldn't wait to get the kid to sleep and get out to the garage to hear it run for the first time.

The first start was awesome, its pretty unusual for me to get a bike to light on the very first kick, so I just about crapped myself when halfway through the second kick ( was in gear the first kick!) she caught and lit right up. Wow! My first impression was how raw and potent this thing sounds, for a stock muffler and rotary valve it was very loud. It revved up so quickly also it was pretty impressive. I could just tell this was a much more highly tuned motor than the other bikes i've worked on from this era. I almost couldn't resist shutting her down, the key didn't work to turn it off either... I'll have to look at that later. A little choke killed her right out so the jetting must be pretty close. Now to finish up the last few things.
Lyle helped his dad by offering some constructive criticism and throwing toys on the ground.

The light was an easy fix, swapped it from the GP and it lit right up. I swapped the tail light bulb about 3 times because for some reason i had a whole drawer full of bulbs with good brake light filiaments and no tail light filament. Why the hell would i have kept those?

The front tube was shot... not only was it the wrong tube completely (2.25x17- moped sized- in an 3x17 tire!!!) it had no rim strip whatsoever, and was rapidly degrading into its component hydrocarbons. MotorWest motorcycles hooked me up with a new one and even stayed late so I could come pick it up.

The clutch took some adjusting, and I went over everything a few times because my friend had disassembled the bike and I wasn't sure what he had messed with. The first few drives around the block, she was feeling healthy. The cylinder was making good torque, slipping the clutch when the powerband hit, and sounding healthy throughout the revs.

I finished up the bike just in time for the Cranks Weds night moped ride on March 14, 2012. Literally got the bulbs replaced just as it was getting dark. Caite and I got her folks to watch the kid for the night and we saddled up for our first ride together since before she got pregnant. Awesome, so much fun! I was hoping to get some shake-down time in before Frozen Snot ride on the following Saturday,

The ride was awesome, simple and chill, went to a bar with a free grill and made some meats. The weather was record high of 75 degrees (in milwaukee, in march! ) so there were a ton of people out and we were all feeling pretty awesome. The bike did well, obviously the enduro gearing was silly short, first gear was a complete joke and I had the piss revved out of her keeping up with the mopeds at 45. The clutch was completely screwy. My 'fix' didn't hold up to an entire night of kickstarts. She started slipping and with it, the clutch was hanging up. I think the slipping bushing allowed the basket to move in and out with the thrust from the helical gear, so when I was engine breaking, the clutch locked up and was hanging at stop lights. Wouldn't have been a big deal with just me, but trying to do all that shifting with a girl on the back was a lot of work. Took a couple stalls-combined with slippy kickstarts- to get the hang of the rotary shifter. Plus for some reason the hanging clutch was causing her to go into 4th gear instead of 1st gear on the first down from neutral. Weird.

 .. more coming soon!