It seems hard to believe that it has already been six months since I dragged home a rusty non running 1980 Honda CB650 Custom that I bought sight unseen at a local junk auction for the princely sum of 150 bucks. If you didn’t see it back then click on this link to see the before pictures. Of course along the way there were various challenges & fun but I had a blast getting this one going and as unlikely a candidate as it was for a scrambler conversion it really did turn out that the whole was greater than the sum of its parts!
Normally I am a man of way too many words so how about if this time I just show you some pictures interspersed with a few tidbits of technical information?
1980 Honda CB650 with 1974 Honda CB750 gas tank & a set of 1979 CB650 standard wheels.
1980 Honda CB650 Custom Scrambler
The handlebars are courtesy of a 1970 Honda CL450 I just happen to have lying around. The tires are Shinko 705 adventure touring tires.
I wish I had a plasma cutter like this at home!
The green paint is a mixture of gloss green & flat black tractor enamel, & the exhaust is from Mac.
they don’t make machines like this vintage Lincoln welder anymore.
Don’t let the nasty looking lowers fool you, the forks have new seals, Progressive Suspension springs & fresh 10w fork oil. I decided to keep the 650 Custom fork legs for the scrambler conversion since they are longer than the 650 standard forks. When I raised the rear by switching to the 17 inch wheel & taller tire it helped to compensate for the extra rake of the custom and gave more ground clearance.
At this time I would like to give thanks to the wonderful folks who provide me with my day job that makes all of this possible.
Safe Harbor Access Systems for allowing me use of the old warehouse and some production areas for this photo shoot. Click here to see the stuff I spend all day drawing blueprints for! And if you see anything you need let them know where you got the information.
Here’s some more of that headlight bracket drillium that I showed you in my last post.
speed holes make it faster right?
I couldn’t stand the 85 m.p.h. speedometer that came on this bike, plus it was making a horrible squeaking sound, so on went the 140 m.p.h. speedo & tach from a 1976 CB750F, with green faces of course.
Do you have any idea how hard it was for me not to attack this with the polisher?
K&N air filters hang off the back of the original carburetors, to learn what I did to them just click here. Other than a re-jetting
& a Mac pipe the engine is bone stock in all of it’s 11,000 original mile glory.
Slug & liquids? Sounds like the results of cheap beer & too many hot wings…
I put a lot of speed holes in this one ’cause I wanted it to be really fast 🙂
Holding up the rear is a set of Progressive Suspension 412 shocks with the heavy duty springs. I have been very pleased with this suspension, it gives a nice cushy ride over some pretty rough bumps but is still firm enough to rock out on a set of curves. Well at least as much as you can with a bike like this.
Sometimes you just find the perfect graffiti to really set a picture off.
One thing that I have discovered while working on this motorcycle is that deliberately building a rat bike is actually a lot harder than it would seem. In all honesty, a deliberately created rat bike should properly be called a neo-rat bike. A real rat bike is a natural creation, a collection of found art held together by grease, road grime & baling wire that accumulates over decades and tens of thousands of miles. People like my self who drag up old bikes & mechanically restore them while leaving the patina semi-intact are actually just posing. But what the heck it’s a lot of fun! Even so the siren song of the polishing machine, paint gun & steel wool are very hard to resist. Have you ever tried to clean just the inside of a dirty weather-beaten old engine cover and then tried to reinstall it so that it looked as if it had never been disturbed? It ain’t as easy as it sounds. Leave the chrome rusty, oh the horrors! Working hard on your sheet metal & then covering with flat or semi-gloss paint instead of making it shine like a brand new penny is very counter intuitive, but sometimes we really enjoy the results.
Here’s some of that exotic metal called drillium.
Now let’s get back to my screwing up a perfectly good tank. As I mentioned in part one the original plan was to cut the rear subframe off and install a custom one for that straight framed 60s & 70s look. When that didn’t happen I took my cut down stock seat & had it recovered in black & green & fitted it to the bike & I actually did my shake down runs and a good bit of commuting on it as it was. Still every time I looked down & saw the bottom edge of the tank was nearly a half an inch above the nose of the seat it bugged me. You see even on a rat, craftsmanship counts. It’s one thing if it has dent’s, rust & flaking paint, but if you modify something or deliberately create a faux patina on something you must do it correctly. For example it’s okay to fog some flat black primer directly over a piece of rusty pitted metal but it is totally unacceptable to get a bunch of paint runs while doing so, because that smacks of sloppy craftsmanship. To me, being my own worst critic, that large seat to tank gap was a sign of very sloppy craftsmanship & it had to go. After experimenting with different thicknesses of rubber isolator for the rear mount I was able to reduce the gap down to about a quarter of an inch. Still too sloppy for me so I took a small body hammer & dolly & started rolling the rear seam of the tank down, figuring that I could repair the green portion of the paint by blending. I actually thought it was going to work but when I was almost finished the seam split. I probably could have silver soldered it closed & coated the tank with a sealer, but my boys kept insisting they did not want to chance a gasoline shower at 60 m.p.h. so it was off to ebay to find another tank.
Buying a gas tank for a motorcycle on ebay can be a very scary proposition. When I was rebuilding the Minimum Ninja, I bought three before I got one that was even usable. The sad part is that I had already left the sellers good feed back before discovering the problems. If I were doing a serious show quality restoration I would do my best to source a N.O.S. tank from a vintage parts dealer before buying one at an online auction. Since this was not a restoration I was hunting functional with a few light dings and no rusted out spots. The one I found looked alright, it had a few visible dings, & some rust on the inside but it was good & solid. I went ahead & put in the rear mounts so it would fit a CB650 this time paying very close attention to how it lined up with the front of the seat.
arrrgh!
Putty smeared all over the tank & I still missed a couple of spots.
Since it was going to be acid washed & lined to keep the rust out of my gasoline, I decided to strip it down & fix the two or three visible dents on the exterior. Then I started removing the paint to fix dents only to find someone had already fixed a bunch of dents. There was already bondo everywhere! Discouraged I actually got back online & began looking for another tank. The problem is that I had already pre-registered for the Bull City Rumble this coming Saturday. So I just stayed up late last Friday night & fixed everything, acid washed it, put in the tank liner & had it ready to paint first thing Saturday morning.
the black primer was actually kind of cool looking
Since I was doing all this extra work I wanted a nice durable semi-gloss dark green that was in line with my original vision for this bike. Being an old country boy I really like the Majic brand tractor & equipment enamel, it is a catalyzed enamel that although it has a long initial drying period becomes very durable. The downside is of course that you are limited to tractor & implement colors. But that was okay since I never found an off the shelf semi-gloss paint in the color I wanted anyway. instead I poured some John Deere green into a mixing cup & kept adding matte black until I got the shade & sheen that I wanted.
After seeing how it looked I decided not to put the stripes and the airbrushing back on it this time, in fact I even color matched the emblems before re-installing them late Sunday afternoon after giving the paint 24 hours to dry.
As I sit here writing this on Wednesday the Suburban Assault Scrambler is sitting in the carport, yesterday I put gas in it for the first time with the new tank, and rode it to work today. At lunch time I took a bunch of pictures of the finished product sitting in various industrial locations, but you’ll have to wait a couple of more days for those pics. Then I have to rest a little bit & get ready to start on the next project!
Some of us just have to do things the hard way, it’s in our blood and it will not be denied. Take me for example, while by no means wealthy in money I could probably buy any new motorcycle I wanted just sign the dotted line & add another automatic draft to my checking account & ride. But even the new retro bikes don’t have the pull on my soul that the old ones do, they aren’t part of my memories, & they don’t need my love to get back on the road. I don’t know about you, but for me the turning of the wrenches, watching dial gauges & degree wheels, the smell of parts washer fluid & the massaging & painting of old sheet metal bring me just as much pleasure a actually riding the finished product. When I finish one project, or sometimes even before I am constantly scanning Craigslist, Ebay, the local trader papers, & the internet message boards to find the next one.
Sometimes I do very irrational things that create far too much work for myself even by my own masochistic, self flagellating standards. This is the story of how I modified & then destroyed a fuel tank for my CB650 Scrambler project, & then had to fix another one.
Let’s start from the beginning, first there was my junk auction CB650C with this very holey tank.
As you can see there wasn’t much point in trying to fix that one so I used it for target practice & threw it away. Initially my plan was to turn this bike into a shiny polished cafe racer style custom with a big ’70s tank & some clip-ons, so I ordered up a 1974 CB750 tank from Ebay & set it on the bike just to see how it would look. Of course it wouldn’t work with the stock seat so I broke out the sawzall & cut 2 inches from the front of the seat. At this point I was still planning to cut the rear sub-frame off & put in a tail loop to support a proper cafe racer seat with a bum stop, because I had the Ninja for me & Mrs. Psyco to ride around on two up. Here’s a shot of the initial mock up.
old 750 tank mockup
By the time the above picture was taken fate had intervened in two distinctive ways. First we’ve had one of the wettest, nastiest, stormiest, summers on record. The dirt road that I use to get from my hole down in the swamp out to civilization, has been an almost constant quagmire because we have not been without rain long enough for it to dry completely up. This is not an environment conducive to the cafe racer style of motorcycle as your only bike. The second factor was the sale of the Minimum Ninja, I really wasn’t crazy about selling it, but the gentlemen who bought it from me was like a kid going, “please Santa, I’ll take great care of it I promise,” so I finally gave in & let him have it. To his credit he does keep it much cleaner than I ever did. But now I had to get something rolling & fast, preferably something with two up capacity that would roll down a dirt or gravel road just as good as a paved one. Decide to do a flat green rat bike that require minimum cleaning.
I had already made a new rear tank mount at this time by bending the CB750 mount down & brazing in a sheet metal angle the the proper size hole in it.
cb750 to cb650 rear tank mount clamped
My ugly brazing
The problem was that at the time I paid no attention the the seat to tank relation, something that would come back to haunt me later. After I changed my mind about the direction of this project but before really fitting everything together I decided to go ahead & change the color, but since I was doing a “rat bike” style build not to fix any dents or chips & just spray can paint it.
tank number 1 taped up
So I taped off the graphics & cap being careful to trim the tape around the nicks and chips hoping that it would look like the new color was original & spray bombed it with what I thought was a flat dark olive color
much lighter than I was expecting:(
About this time, I purchased a “skull pile” stencil from Airsick Stencils & decided to play around with it some, so I popped the tank off & taped it up following the instructions on the Airsick website for using these reversed stencils they sell, & sprayed my main color Createx Wicked Gold.
This color required a lot more thinner than the other Createx colors I’ve used in the past
After spraying the color I then put the stencil back in place and turned my air pressure down a little bit and sprayed in some opaque black to create the details.
laying in the skulls
Here’s what it looks like when you take the stencil off.
Just In case you were wanting to know the airbrush is a Paasche VL & yes I am very happy with it.
After finishing up and giving the paint a few minutes to set up I peeled the tape off.
peeling back the mask
If you try this at home just remember that most commercially available airbrush paints are designed for fabric use & require heat to set them and make them permanent, so go over the surface with a hair dryer or hot air gun & get it good and warm if you don’t want your paint washing off later.
Most people go back over these skull piles & fill in little details with the airbrush & some freehand stencils. Me I cheated a little bit by doing my detail work with a black extra fine point Sharpie, before spraying on the clear coat.
It looked decent enough for a rat bike I thought
airbrushed tank on cb650 scrambler
It’s kind of a shame that I destroyed this tank while attempting to correct the big gap between the bottom of the tank & the top of the seat. Oh well if you’re gonna cook an omelet you gotta break a few eggs. I’ll come back in a day or three and tell you the rest of the story.
Wait a minute what does a blog with a name like agrowingfamily.com have to do with motorcycles? Yes this is Joseph R Fehlen’s personal blog, in which he shares his family, faith & his motorcycling experiences with the world. I recently read his book Ride On; A Motorcycle Journey to Awake Your Soul and Rediscover its Maker, and highly recommend it to you. Most of the time I deliberately avoid folks who try to mix religion & motorcycling as they often cause me indigestion by being excessively legalistic & quite frankly taking all the fun out of motorcycling by becoming too focused on group rides, formation discipline, driving 10 mph below the speed limit, holding up traffic etc. Instead we get to read about a Minister of God whom actually rides his motorcycle day in & day out up in the great Northwet corner of America and the lessons he has learned from life’s roads.
Hello again everyone, Lets restore a set of carbs for this old Honda! Yes I had already turned them over one time & popped all of the bowls off and blew them out with some carburetor cleaner and put them back on to test run the old bike & see how it sounded, but it was a running a little lean with the pod air filters, plus I was installing a new exhaust system and needed to re-jet anyway. But the single best reason I have found to go to this extreme is that there is almost nothing else that will make an old motorcycle run like new again the way a complete carburetor refurbishment will. In fact the only thing better is a new set of carbs, which if you pull your old ones apart & find severe damage or wear to the castings, is your only choice.
Here you see the four carburetors, along with a flathead screwdriver, a JIS screwdriver, a set of mini wrenches and a ratchet with a socket. This is not everything you need to completely disassemble them but it’s a good start. The patient is my own 1980 Honda CB650 Custom with a set of Keihin PD mechanically operated carburetors. Although these a very similar to the piston valve or round slide carbs used on a number vintage motorcycles these do have a few differences from the older ones. This will not be a complete step by step guide to restoring every single piece. If need to learn the basics of carburetor repair I suggest that you start by clicking here.
Instead I will focus on how to disassemble the set of carbs, and point out some of the different features along the way, along with a few tips and tricks to make the job more successful. Please note that successful does not mean easier. This is not rocket science but there are no shortcuts either.
The first step in getting a set of carburetors apart is to remove everything you can from the choke & throttle shafts. Here I am using a JIS screwdriver to remove the choke butterflies. What the heck is a JIS screwdriver you ask? Just click here to find out!
Please note that these screws are often punched from the backside at the factory to spread them out & keep them from coming loose & falling into a running engine. This often makes them a pain in the butt to remove.
Next take the tops off and remove the long screws that connect the slide lifters to the throttle shaft.
pliers marks, I hate pliers marks
Be sure to inspect the shafts for damage like this before you start pulling the unit apart. At some point a previous owner had used a pair of pliers to move a sticky slide. To avoid damage to the bushings etc. use a strip of sand paper or emery cloth to remove anything you find like this prior to dis-assembly.
Once you have everything loosened or removed from the shafts it’s time to remove the brackets that hold the rack together. On this set there is one large bracket on the engine side & two small braces on the air cleaner side.
Then you can slide the two outer carburetors off the shafts and lay them out along with all of the parts that go between each carb. Lay everything out on your workbench in the order that it comes apart with everything facing the direction that it goes back together correctly. It just makes life so much easier. In fact if you have never done this before I suggest taking a copious amount of pictures at each stage of dis-assembly to help you remember if the doohickey is pointed toward the watcha-ma-callit or the thinga-ma-bob.
Here’s a shot of the two middle carbs with the vent hoses in the foreground and everything else behind them.
On this motorcycle the throttle return spring is fitted between this bracket and the number three carburetor. Carefully drive out this rolled pin to remove the return spring and remove the shaft completely from all the carbs.
Here is a shot of all the major components laid out on the bench more or less in order. Always keep the parts from each individual carburetor together, never mix them up because there are some small differences in every set even if it just wear patterns. Some machines (but not this one) may even have different jetting between different cylinders so just play it safe and don’t mix your parts.
At this point instead of a big complicated looking rack of carbs, you are now just rebuilding 4 individual carbs with only a few differences from you average
This is one thing that is found on the early emission controlled Hondas (late 70s & early 80s) is this pilot mixture screw with the tab on it to prevent it from being rotated too far in on direction or another. The float bowl must be removed first to remove these screws. Of course if you doing this for an off road, race only machine 😉 you can carefully grind the tab off before re-assembly.
Another big difference on some machines is the presence of an air cut off valve often found under a cover like this. The purpose of this valve is to temporarily restrict the flow of air through idle air circuit when the throttle is suddenly snapped shut. This helps prevent that lean backfire that occurs on some motorcycles when you suddenly let off of the gas.
These valves were later eliminated from some models but the side cover is still there, but it’s just blank. Some folks will actually remove these and solder the holes closed, then re-jet the carbs extra rich to run without them but IMHO that is not the way to go. Yes I know that at 30 to 40 dollars & up each this is a damn expensive little part, but take my word for it if you replace them you will notice difference.
One nasty little surprise is the presence of pressed in pilot / slow / idle jets. pick your terminology but all three words refer to the little brass tube you see in the picture above. If you are restoring a completely stock bike with stock mufflers and airbox then I will recommend you do everything in your power to clean it without removing it. But if you cant get it clean or if you’re like me & think stock sucks don’t fret it can be changed. As far as I know there is only one source for the pressed in jets and that is Sirius Consolidated, one of my favorite purveyors of all things for motorcycle & powersport carburetors. Click here to check them out.
If you’re planning to change them out anyway grab them with a set of pliers, twist a little to break them free & pull them out.
I finally decided to break down and try ultrasonic cleaning. This is a cheapie from Harbor Freight. For my cleaning solution I am using 1 to 1 mixture of Simple Green & water. The only real drawback to this one is that you can only get 1 carburetor in it at the time, and even then the entire carb is not submerged. I just ran every one for the maximum cleaning cycle of 480 seconds and the flipped it over and ran it for the max cycle again. Be sure to put all of the parts for each carburetor in the cleaner, including all of the internal parts, along with the fuel & air vent tubes that run between the carbs.
Being the meticulous and detailed asshole that I am even after the ultrasonic cleaning I blow everything out good with an air gun and rinse well with aerosol carb cleaner. I also use Simple Green in my parts washer & have discovered that if you don’t rinse the parts afterwards they sometimes have soap residue on them. Plus I just like to be sure that all passages are clear.
Here’s a fresh clean carburetor ready to be re-assembled with all new jets. FYI with the K&N pod filters and the Mac Exhaust I am using #42 pilot jets and #120 main jets. and put my initial pilot mixture screw setting at 2 turns out. This set up turned out to work very well with only minor adjustments after starting the engine. I actually arrived at these numbers for my initial set up after perusing hundreds of posts at the HondaCB650.com & the SOHC4.net forums taking notes and basically picking out the jet sizes most commonly reported to be working successfully in these carbs on this bike with pod filters & aftermarket exhaust. Internet research is such a great time saver but remember to put your ego aside & your bullshit detector on high. You’ll have to wade through a river of fiction to get a few drops worth of facts.
Even armed with these numbers I was prepared to pull the whole thing back apart several times to get it right, but I got lucky this time. That does not mean these jet sizes and settings will work for you & your CB650, but they are as good a starting point as any. Back in the pre-internet days I was re-jetting a moderately modified DOHC CB750F and wound up pulling the carbs off and putting them back on a dozen times before I found the perfect combination of performance and street-ability. If you are modifying your motorcycle you should be prepared to do the same.
This was not a cheap process either, I replaced every single piece of rubber & all of the jets in this set of carbs. The cost just for parts set me back over $300 bucks plus shipping. The jets, air cut off valves & the accelerator pump, all came from Sirius Consolidated, everything else is genuine Honda OEM parts, even the o-rings on the crossover pipes.
This is how the air cut off valve diaphragm, spring & o-ring fit into the body.
I preach a lot about service manuals, and yes I usually try to practice what I preach. This allowed me to verify that the float height really was supposed to be 12.6 mm like most of the fine folks on the net were saying. Trust but verify!
Lets talk about that accelerator pump thingy a little bit. It is usually mounted on the #2 carb like this one. It’s purpose is to squirt a little extra fuel into the engine if you suddenly yank the throttle open. Even though it only enriches one cylinder it helps to reduce the lean stumble that results from a sudden inrush of air when you twist the throttle as fast as you can. It’s also great to squirt a little extra fuel into the intake before starting a cold engine if needed.
It lives under this little cover on the bottom of this carburetor.
Here it is laid out on the bench so you can see how it comes apart.
This shot is just to show you the differences in the #2 float bowl & the rest. These differences are there for the accelerator pump circuit.
At the time of this writing I have found no source for exact replacement parts for the CB650 accelerator pumps. I think this one is for a CL/CB450. The diaphragm is the same but the shaft is longer. so it will have to be cut to match the stock length.
I marked it and then clamped it into a vise with rubber jaws & then filed it to the correct length. Just remember if you get over excited & cut too much off that you have just screwed yourself out of the price of 18 bottles of Guinness Extra Stout.
Modifications are always a pain in the rear. These air filters don’t clear the choke linkage so even more modifications are required. It’s a vicious cycle I tell ya, and not for the faint of heart or the flat of wallet. Modifications beget more modifications & before you know it you have a complete custom motorcycle that will hopefully run at least as well as a stocker. ;0
Just a few more tips for you, re-assembly is pretty much the reverse of dis-assembly. Make sure you wind the throttle return spring up enough to close the slides when released, and always use some form of top quality name brand thread locker on these little screws holding the butterflies in place. If these come loose they can turn your fine running engine into junk if they get into the cylinder.
This picture shows how the spring connects the left & right choke shafts together. Once you have it all back together you should try to “bench Sync” the carbs. Basically you want to get it adjusted so that it appears the all of the slides are lifting at the same time & closing the same distance. A picture of the synchronization adjuster is shown somewhere further down in this post.
Now make sure all of the clamps are on the intake boots loosely, hook up your cables, & then lube the carb spigots & the inside of the rubber boots on the head.
Now push, pull, cuss, twist, shove & pray. If you are reusing the old boots they may be hardened and make this process a little harder. sometimes heating the rubber with a heat gun helps. Just remember that if they are damaged in any way and do not seal properly you must replace them.
Here I am clamping everything down getting ready for the initial start up. I actually started the engine and let it warm up a bit before moving on the vacuum synchronization process.
Once I was satisfied that the engine was basically running okay & that there were no fuel or air leaks I shut off the engine & temporarily installed these adapters in place of the plugs on the engine side of each carburetor. Then each adapter gets a hose between it and this set of gauges.
Before you get started with this procedure it is usually a good idea to have a fan pointed at your engine & running. Sometimes this can take awhile & you don’t want to risk engine damage.
This picture shows the location of the adjuster screw in each carb. Make sure that you always tighten the lock nut securely when you are done adjusting the carbs. The number two carburetor does not have this adjustment on it, it is the baseline and you want to match the other 3 carbs to it. When you get it done all of the needles on all four vacuum gauges should rise & fall at the same time and to the same readings. Now you can put all the tops back on the carbs & begin road testing. Most run just fine, perhaps with a little tweaking of the pilot mixture screws and idle speed if needed. Just make sure that everything else, especially the ignition system is working properly too before road testing the carbs.
This bike is now 90% complete and I have actually put a couple of hundred miles on it in the last week or two. The shake down runs have been encouraging once I got the final adjustment of the carbs correct and finally broke down and replaced the original 1980’s plugs with a fresh set. Speaking of the carbs, I did a full teardown & took lots of pictures and I am in the middle of writing a carburetor restoration post now, hopefully to be completed later this week. Ditto for the fuel tank mods & the paint.
Let me apologize for the fact that progress on the bike has outpaced my postings, but at this time life is so incredibly full of good things and huge opportunities that it’s a bit overwhelming for me. I will be showing you the major points that I changed on this bike asap.
BTW; it is a great commuter!
The SAS & the Minimum Ninja bask in the sunshine outside my office.
Welcome to the Asylum 