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Old 04-08-2015, 11:10 AM   #1
Nihon Newbie OP
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Project 1972 Honda CB100 K2

Planning to pick up the bike today, have to start a build thread...researched a lot about what I might want to improve and I'm leaning towards a budget custom build, mostly aesthetic, not full café style, but less dorky than stock, with some modern touches like a small digital tachometer, and possible LEDs for signals/speedo baclights. I want to do a custom paint scheme, not reproduce the original colors...have access to a paint booth and heated cure room at work, so hopefully able to use that to my advantage and spray them myself...The tank may have a little rust left in it, so that will be addressed before repainting...

Mostly cleaning/refinishing all exterior surfaces with new paint or powder coat
Repainting side covers and fuel tank
Replacing leaky seals/gaskets
New chain
oil change
SS flanged hex bolts to replace all the pan head screws holding the engine case covers on
full go-thru of the wire loom - Apparently the lighting doesn't work
polishing existing chrome on wheels/fenders
rebuilding both drum brakes
new cables
Polishing/cleaning out aluminum switchgear housings
New grips
different but probably "period accurate" rear shocks
replacing frame/engine/swingarm bushings
perhaps the biggest one...Exhaust.

The muffler is painted black, no idea why, but it's supposed to be chome. I'd like to find something newer for it, but I don't know anything about re-jetting carbs for new exhaust systems...so we'll see. I just want it to sound good and not make any less power than it already does, heh.

This "restoration" will not be a full factory job, just don't have the $, and I want it as a daily rider for the next couple years. Not looking to modify the motor, either, even though I know head/piston swaps are popular with this bike. I mainly just want it to be up to my clean standards, and mechanically sound. Stoked to ride it home today, then immediately to the local moto group weekly meetup
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Old 04-08-2015, 07:47 PM   #2
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Well update #1 isn't the best news, lol. The head gasket is weeping on the forward edge, so that will need to be fixed...Almost a bit more work than I really want to take on with this bike, but I think it will all be worth it in the end, I'm just already wishing I had the same amount of time to throw at this as I did when I was unemployed and "restoring" my 600RR 2 years ago...

Either way, bike is a BLAST to ride! There is no throttle return though, which is sketchy, and will need to be fixed ASAP. Order of operations has, I guess, now been decided...First thing I'm going to try to tackle is getting the thing tuned up and running right...It totally bogs and chokes at anything more than 40% throttle. It also leaks a fair bit of oil, but I'll deal with that after the side cases have been restored/refinished. Going to drain the oil, take the side covers off, poke around a bit, ride it for a couple days, then start just taking everything apart...The OO tried to paint everything with crappy silver paint to hide rust, so the wheels need to be taken apart, the spokes all sandblasted clean, and lots of things sent off to be re-chromed while I'm working on sanding, blasting, and re-painting the tank, side covers, frame, engine case covers, and front forks. The motor work will have to wait for the mean time, I just want to make sure it's sound before I pull it out of the frame.

The electrical will all need to be gone through, as well...Which I scared of. I'm tempted to just make a whole new reproduction harness, as I have access to the materials at work, but I don't know diddly about what that entails, so we'll see. None of the lighting works right now, so I want to see if some simple but targeted application of contact cleaner might get a few things working before total disassembly...

The exhaust I may leave black...re-chroming is $$ and I want to do just the wheels/rear fender for now. I'll be buying a ton of exhaust gaskets, too, since it seems the whole system needs to come off just to change the damned oil...Epic design fail, if that's actually the case. On the other hand, it says the oil type and capacity right on the handy oil dipstick, so that was a pleasant surprise!! It only holds one liter of oil, so changes will be affordable. The chain needs to be replaced, as well, as the current one was very rusty at some point, and crudely painted over. Luckily a simple roller chain from DID is only about 20 dollars. Sprockets look to be in great condition as far as wear goes, they're just dirty and in need of a good scrubbing down.

So far, I'm looking at about 200 dollars in parts I need to order right now, plus whatever re-chroming will cost, so that's half of what I planned to put into it in total. I'm pretty confident that I'll be able to put 3 days into it this weekend and maybe come up with an accurate investment for time needed to make this all happen, and then set a goal accordingly...For right now, I'll say I'd like to have it all back together and be riding it again in 6 weeks...Fingers crossed!
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Old 04-09-2015, 04:15 PM   #3
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I had the same oil leak problem with a CB125 (essentially an identical bike). It wasn't fixed until I took out the engine, then the head off. I then got some wet & dry (it was pretty fine, like 600 grit) on a piece of glass and rubbed the head and barrel down until the mating surfaces were smooth.

In my case the head gasket was copper and over the years it had corroded with the alloy surfaces leaving quite a deep pit.

Re: taking exhaust off to do an oil change? Nope. You just drain it through the plug under the engine and fill it through the dipstick hole, preferably after you've put the drain plug back in.
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Old 04-09-2015, 10:08 PM   #4
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Quote:
Originally Posted by Bendernz View Post
I had the same oil leak problem with a CB125 (essentially an identical bike). It wasn't fixed until I took out the engine, then the head off. I then got some wet & dry (it was pretty fine, like 600 grit) on a piece of glass and rubbed the head and barrel down until the mating surfaces were smooth.

In my case the head gasket was copper and over the years it had corroded with the alloy surfaces leaving quite a deep pit.

Re: taking exhaust off to do an oil change? Nope. You just drain it through the plug under the engine and fill it through the dipstick hole, preferably after you've put the drain plug back in.
Indeed, there are several oil leaks at the moment, including the head gasket. I'm going to likely use the same trick as you when I pull it apart. Good to know about the exhaust, thanks!
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Old 04-09-2015, 10:20 PM   #5
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Quote:
Originally Posted by Bendernz View Post
I had the same oil leak problem with a CB125 (essentially an identical bike). It wasn't fixed until I took out the engine, then the head off. I then got some wet & dry (it was pretty fine, like 600 grit) on a piece of glass and rubbed the head and barrel down until the mating surfaces were smooth.

In my case the head gasket was copper and over the years it had corroded with the alloy surfaces leaving quite a deep pit.

Re: taking exhaust off to do an oil change? Nope. You just drain it through the plug under the engine and fill it through the dipstick hole, preferably after you've put the drain plug back in.
Ah memories...that was my Wifes bike, only bike she ever rode.
Then my mate got hold of it and went mad.
Must have sat around for 13 years prior to you getting it sorted.
( got a C200 in the shed now....)
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Old 04-10-2015, 11:15 AM   #6
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Trying to research how I can fit a tachometer to the bike...there is no mechanical pickup, but I've been told about digital ones that read based off the ignition coil...

Disassembly starts today after work...Kinda bummed that I won't be riding it for a while, it's so fun!
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Old 04-10-2015, 06:26 PM   #7
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Insurance for the bike will be $40 per year
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Old 04-12-2015, 10:23 AM   #8
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Page deleted entire post...

TL;DR : 10 Hours of working on the bike yesterday, I'm sore as heck, the bike is mostly apart. Leaving motor in frame for now so I can work on it without it falling over. Electrical was a nightmare, all the wires painted black from overspray, many bulbs burnt out, and signals still don't work. Headlight bulb is soldered into it's socket, thanks a lot PO, lol.


I found what looks like a very small and slightly more modern rectifier, spliced into the stock loom...It's a square shaped, .25 inch thick black block with 4 metal tabs coming out, and 4 leads from the loom attached to those 4 tabs. Trying to figure out a more suitable replacement for it that utilizes a modern connector, not just direct wiring.
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Old 04-13-2015, 06:20 AM   #9
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hell that is a really nice bike to start with. Popping the head is no big deal.
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Old 04-14-2015, 08:23 AM   #10
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hell that is a really nice bike to start with. Popping the head is no big deal.
Indeed, thanks! It's not really missing much of anything original except for a couple nuts and bolts, and the air cleaner element. I currently have it down to the frame and the motor, and a shopping cart with about 32 different OEM parts that need to be replaced soon. I just started sandblasting all the parts I want to refinish, save for the frame, which won't fit in the blast cabinet at work. Would like to have it powder coated, but we'll see what my budget has to say about that. There are a few rubber seals and bushings for the front forks that aren't really available anymore, but I'm still calling around to parts houses online in hopes of finding some NOS treasure, ha!

The PO dropped off a box of spares/original parts last night...so stoked! The rubber air intake funnel for the carb, the original carb, service manual, owners manual, original keys, a vintage gasket kit, assorted O-rings, original reg/DMV papers, extra OEM side covers with broken tabs (bummer, but fixable), original petcock and fuel filler cap...I'm not aiming for a full factory restoration, but it's cool to have all this stuff that only adds to the provenance of the bike!

I've only ever pulled motors out of scooters, never a full sized bike, so that's going to be interesting...I sprayed penetrating oil onto all the mount bolts, so hopefully after a few days of soaking, they'll break loose easily. Planning on buying a good assortment of Loctite sealants, gasket eliminators, RTV, and such to help with the motor refresh and stop all these pesky leaks once and for all. This is only my second air-cooled bike, and I'm already loving not having to deal with anything coolant related!!
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Old 04-18-2015, 02:28 PM   #11
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So I've put another chunk of work and research into the bike...Looks like I'll be doing a 12v electrical system conversion, mostly to be able to run commonly available LED lighting, and a brighter headlight that actually does something at night. Having a modern battery that will be compatible with my tender will be helpful, too. I bought a CB350 stator, which is thankfully a direct swap in for the CB100, and requires only some minor modification to the main loom to get it all working...in theory, knock on wood. The largest expense is the regulator/rectifier unit that it looks like I'll need to purchase, which is $92...So we'll see if the budget allows for that at all.

I'm about to go try to drain and disassemble the front forks, which are actually oil filled! The sliders are a bit rusty in some places, but they function fine...If I can't take them apart, I'll at least change out the fork oil and clean the rust off as best I can. I'd like to take them completely apart so I can paint the lower fork receiver, so fingers crossed...

I am waiting on a quote from one of the local powder coat places...At the minimum, I'd like to have the frame, swingarm, and engine cases done. Depending on cost, perhaps also the wheels. I'm fairly confident I can handle painting the brackets, fork covers, plastic side covers, gas tank, and fenders. The turn signals I'm really stuck on are only available from a parts place in Japan, and they would be about $100 after shipping for all 4, and that doesn't even include the LEDs I'd want to put in them...I have a feeling I'll be going with cheaper signal units and just doctoring them to look half as nice as the Daytona units I'm lusting after.

Tomorrow I'll be taking the tires off the rims and disassembling the wheels. I'll need to take apart the drum brakes, too, as they'll need to be very clean before being prepped for paint. I'm really hesitant to paint the wheels, as I would love to keep them chrome, but the chrome on there is already painted over, and having them re-chromed is too much $$ for me right now, so I think they'll be painted...Might try the "chrome finish" paint that Rustoleum makes, and just bake the shit out of it in the oven at work once it's on the rims. Still stuck on color schemes for the wheels though...
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Old 04-20-2015, 12:10 AM   #12
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Finally got around to picking out some photos of the disassembly progress I've been making...I spent about another 8 hours working on it, and another 8 hours researching stuff I need to do/buy. I also broke my first part which will be expensive to replace, so that sucked. Most of the day was spent cleaning the drum brake hubs, plus a couple hours disassembling the front forks, which necessitated cutting off the chrome sleeve that was rusted solid to one of the fork leg lowers...Might have to fork over 70 bucks for a new set :

Anyway, pics...

























In the pics you can see how nasty the brakes were...way too much grease in there, and the hubs were full of dust/dirt. I'm going to make my own felt dust seals to try and prevent this happening again...

You can also see how the headlight bucket is cracked in several places, and has a few dozen coats of black paint on it, lol. I bonded the cracks and filled in a few chips with 3M DP-805 methacrylate 2-part adhesive, then sanded it all down. The cracked areas were reinforced with single plies of 2.5oz carbon fiber and a 3 hour resin, vacuum bagged and cured overnight at 110F. The plastic degrades when exposed to acetone, alcohol, paint thinner, etc. so I had to hand sand the whole bucket, then a light media blasting to even out the surface. I plan to paint this bucket to match the tank later on.

I think need to use an impact screwdriver a lot next weekend...all the phillips head screws are being pulled out of the motor and replaced with either flanged hex bolts, or allen heads. Also, the damper rod screws in the bottom of each for leg are totally seized and need to come out and be replaced.
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Old 04-25-2015, 02:03 PM   #13
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Drained the forks last weekend, got the snap rings out that retain the top seals, but I can't get the damper rod screw out of the bottom, looks like I'm going to have to use a screw extractor to back out the old philips heads that are in the forks, as well as holding all the engine cases on. All the old fasteners are being replaced with their stainless equivalents, or better, in the case of all the screws. Planning to replace all of those with small flanged hex 8mm bolts. My cost estimate for the fastener replacement is still up in the air, as price varies widely from supplier to supplier, but I'm guessing less than about $60 for everything I want to replace. Bought fork oil to refill the forks whenever they get all polished up and refinished. The manual recommended 10w-40 engine oil, or ATF, but I bet the fork oil is going to be a way better fluid for the job. Chemical tech has advanced eons in the last 40 years, haha. I also bought this super awesome Craftsman flex-socket in 8mm...I'd love a full set of these! It's just like the u-joint adapter for your socket wrench, but it has the 8mm socket integral to the assembly itself, so it keeps your stack length short for hard to access bolts/nuts!

So far I'm only up to $140 in restorative costs, and most of that has just been tooling, chemicals, and a couple NOS parts on eBay. I got a wildly huge quote from the local powder coating place, so it looks like I'm going to have the frame done, but not the wheels, engine cases, or hubs. The good news is that frees up some of the budget to be spent on better quality parts and paint, which are more important to me anyways. I have about $125 in my Partzilla cart, plus a couple other parts from assorted Honda dealers nationwide. I know a lot of the parts are going to be backordered, so I'm allowing for them taking a few weeks from purchase to actual arrival.

I discussed my battery needs with a helpful guy at Batteries Plus today, too, and it looks like I can buy an AGM 12v 5aH battery for about $50, or a sealed, maintenance free lead acid cell for about $40, and both should more than cover my electrical needs. I got a specific part recommendation on a regulator/rectifier unit from Flying J Customs, and it's about $50 also, plus some small things like, fuses, resistors for the ignition coil and a variable resistance flasher relay...Totaled up, it looks like I'll be in for at least another $305, plus paint prep and paint supplies...My budget was supposed to be $500 for restoration, so I'm still hopeful that I'll come in at or under that! Fingers crossed that the 12v conversion and my paint skills pull through, and don't end up being huge money-pits!

More pics to come tomorrow
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Old 04-27-2015, 06:47 PM   #14
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I hate philips head screws

Uploading pics to photobucket...

I've hit a very frustrating wall...I got the motor out of the frame, but I cannot for the life of me budge hardly ANY of the damned philips head screws out...It maddens me to no effing end why Honda used these to hold the cases together as well as the case covers...I can't do anything to the motor until I figure this out. They're all painted over and way way too tight. I got a screw-extractor kit from Sears and all it did was bore a hole into the screws, and not back them out, what a waste. I have sprayed penetrating oil on them all since day one, tried smacking them, vise-grips on the ones I could...nothing. I am tempted to use an impact screwdriver, but I don't want to break the old, fragile-feeling aluminum cases, nor have I tried torching them either, for fear of weakening the aluminum.
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Old 04-27-2015, 09:03 PM   #15
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Kicking Phillips A$$

In winning the battle with the Honda Phillips head screws is to have a very high quality number 3 Phillips screwdriver (Snap-On or Mac Tool) and get to know your hand impact very well.
If the screw head isn't already stripped just assume that there too tight to loosen with your standard screwdriver and go straight to the hand impact. With the correct sized bit, for the screw head that you are taking out, (brace the motor so it doesn't move around on you when you hit it) and strike the end of the impact HARD, don't worry about the cases they are stronger than you think.

If the head of screw is mildly messed up you can hit a few times with flat drift type punch a few times. This will hopefully do two things 1. smash the some of the mushroomed out Phillips head area back into something more useful that your impact or screwdriver can grab on to 2. shock the threads of any possible corrosion.

Good Luck. (In a positive kinda way)
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