CB750F Project: Part X

Today, after clearing gutters, digging trenches for the water to run away from the house, and getting soaked, I decided to spend a few hours in the garage.

And it appears that it was a wise decision.

First, I was able to finish wiring the front turn signals and the horns. With everything wired and connected, I struggled fitting all the wires into the headlight housing, but I ultimately prevailed.

Second, I was able to find the cause of a glitch I experienced while test riding the bike yesterday -- a constantly turned on neutral light. It turns out that when I installed the sprocket cover, I have accidentally pinched the switch's wire between the engine case and the cover, giving it a constant ground. After I removed the sprocket cover and found the cause, it was as easy as wrapping the damaged insulation in electrical tape, and re-routing the wires where they won't get pinched.

And third, I finally started on fitting the tail section. After cutting out a radius matching that of the fender, I set it down on the frame to mark the location where the tail section would attach to the frame. Initially, I wanted to leave the entire cowl without any visible fasteners, but I had to abandon the idea. When I first planned this, I was going to attach my rear turn signals where the passenger footpegs should be, but faced with the choice of having ugly screws on the cowl, or using the turn signal bolts to attach the cowl to the frame, I opted for the latter.

In the end, all I had to do was to modify some nylon spacers (to fit between cowl and frame), enlarge the existing holes in the frame, and separate the signals from the stems (which are the mounting bolts).

While the end result is not as aesthetically pleasing as a smooth cowl, it looks better than a set of mounting screws.  Tomorrow I'll work on some sort of latch system that will allow me to tilt the tail section to the rear, pivoting around the turn signal stems. I'm thinking O-rings on the stems, and a latch up front. However, if I don't like it, I'll just make a bracket for the front that will bolt to the inner fender.

There is still a ton of work left to be done, but here is some progress.

Working on the seat, part II

There was some trimming to be done on the seat pan, so it would follow the contours of the side panels. The seat pan, being nylon, was easy to cut. Dremel was out of the question, as the high speed cutoff blade melts the nylon, immediately sealing the cut it just created. However, the old fashion approach, using a hacksaw with metal blade never fails. After cutting the pan to the desired shape, I smoothed all edges with a 100 grit sandpaper, to prevent future rips in the seat cover.

Next step was to glue seat foam onto the pan. I opted for using the old KLR foam, as it is more rigid that any foam I can find locally. To adhere the foam on to the pan, I used 3M spray adhesive.

As you can see, the KLR seat is of a completely different shape than what I was looking for. In addition, since I trimmed the seat pan, the foam came over the edges.

After cutting the excess foam, I bolted the seat in place and started on shaping it.

This was done with a metal hacksaw blade. This method, while fast, only gives marginal results. Although the blade cuts through the foam with ease, it flexes too much to achieve any accurate results. To produce the final shape, I used a belt sander with a 100 grit paper on it. I tried using an orbital sander, but the edge of the disk was cutting into the foam too much -- the belt sanded worked much better. During the process, I sat on the seat numerous times to ensure it will feel right. Since I plan to ride this bike, a comfortable seat is more important to me than a good-looking one.

A quick session with an electric stapler, some vinyl, and a lot of cussing later, I had a decent seat to test.

I drove up and down my road (no lights, no front brake - so I was limited), and I really liked the way it felt. 


 

Working on the seat

When I first made the decision of eliminating the seat that came with my CB, I opted for using what I had in the garage -- that is, a spare KLR 250 seat.

Some people questioned my wisdom, while others were curious as to what it would look like.

I must admit that the thought of putting a dual-sport seat on a street bike sounds insane. Nevertheless, the curves worked out rather well, in my humble opinion, and the seat pan was paid for, so why not.

After chopping the seat pan to a single seat length and figuring out its basic position on the bike, I went ahead and molded the rear section. Once the rear section was fiberglassed and painted, I started with reassembly.

As you probably know from previous posts, I spent a lot of time working on the brakes, fixing the carburetors, and all the other stuff that makes the bike run, drive, and stop.

Well, while waiting for some brake piston seals, I decided to work on the seat itself. And here is where the challenges started.

When I first laid down the pan and molded the tail, I had the inner fender removed. It was no surprise that once I installed the inner fender in its place, that nothing fit the way it did before. Faced with the options of either not having the inner fender, or reworking the seat and tail, I decided against removing the inner fender. yes, I can be stubborn and this adds a ton more work. But, the thought of every piece of gravel and sand hitting the frame and battery, was the deciding factor.

So, the first step in this saga was to remove some more material off the seat pan. This went along smoothly (doesn't it always?). I then had to figure out how to attach the pan to the frame. At this point, I have the rear attachment brackets figured out and fabricated, but I still have to work on the front.

I started with some 1/4 inch aluminum flat bar

 Which I then bent in a vise to offset for the frame mount, drilled a hole for the mounting bolt, and rounded off the ends.

 Next, I found the proper mounting point on the seat pan, drilled a hole, and cut the end at an angle to accommodate the angle of the pan.

 And, voila, it worked.

It is attached to the seat pan via stainless steel carriage bolts, which will hide nicely underneath the seat foam. I still have to smooth all the edges and polish the brackets, but I'm one step closer to finishing the seat. 

UPDATE:

Tonight I finished making the front bracket. Actually, I used the "lip" method, where an aluminum lip slides underneath the gas tank mounting bracket, and holds the seat in place by friction. Since the seat is attached in the back by two bolted brackets, there is no way the seat will move. All the lip does is to hold the front of the seat in place, and to prevent it from rising.

First, I cut a piece of 1/4 inch aluminum plate to the desired length. Then, using a double-sided tape to temporarily hold it in place, I marked the location where the lip would attach to the seat pan. Since the seat rises up against the tank at an angle, I had to bend the lip to follow the contour of the pan. Once that was done and the desired amount of friction achieved, all I had to do was to drill two holes in the pan and the lip, and attach the two together with stainless steel carriage bolts. I then cut the excess bolt length to prevent it from snagging on the wiring that resides under the seat. To minimize frame scratching, I used a piece of protective door molding (self adhesive half-pipe used on car doors) on both the front of the lip, as well as the frame bracket.

Next, I'll be cutting the seat pan to copy the contours of the side panels, and carving the seat foam to the desired shape. And then it will be upholstery time.

I took a weekend break from all the bike work, the mundane, and the to-do-list, and headed down to Rhode Island to see some animals.

Here is one of the cute guys that caught my eye.

CB750F Project: Front brakes part II

Finally got to cleaning out the front brakes. Right now, the calipers are all reassembled and ready to go back on the bike.

In the mean time, I discovered some carburetion issues, so I have to take the carbs apart, again. The cause, at this time, is unknown.

Anyway, here are a few pics of the cleaned calipers and the front master cylinder.

CB750F Project: Front Brakes

I'm finally starting on the front brakes.

This is what I found once I took the brakes apart.

Obviously the front calipers are pretty much oxidized, but cleanable. 

 The Master Cylinder is in a tough shape.

 Other than an old brake fluid of very questionable quality, there is plenty of gel-like deposits. On top of this, someone, once upon a time, decided to seal a leaking O-ring with silicone, liberally applied everywhere.

This is what I was hoping to avoid - a complete rebuild. But, the piston has seen better days, so I don't have much choice.

Right now, I'm waiting for parts: new master cylinder cover (the old one is pitted and rusty, with cracked plastic) and a rebuild kit.

CB750F Project: Part IX

Somehow it happened, that I spent the better part of this weekend working in the garage. In the end, however, I discovered some new issues, which leave me quite puzzled.

With the new brake piston and a rebuild kit, I was able to complete the resurrection of the rear brake. Everything went back together smooth, and the new piston fit in perfectly. I replaced the old, rusted piston on the master cylinder, changed all seals, and put it all back together. On the caliper, I got away with a thorough cleaning, replacing the old seal with a new one, and lubricating the sliders. I then bled the brake on the bench, which was quite easy, and prevented me from spilling brake fluid all over my newly painted frame and swingarm.
Fitting the brake assembly on the bike was somewhat challenging, and I had to remove a few pieces off the bike to get it in there right, but in the end it worked out. I did not take any pictures of the process, but what I had to do was to remove the aluminum passenger footpeg mount and assemble everything off the bike. Then it went back on as one piece. To mount the brake reservoir, I also had to remove the lower rear fender. For the brake lever pivot, all it took was to brush off the old, dried grease, polish the inside of the bushing, and apply clean, new grease. It now operates like a dream.

While I was at it, I installed the rear wheel. Of course, I took it apart first, cleaned all the bushings, spacers, and bearings, and packed them with fresh grease. Sometime in the past, someone busted the threads on the rear axle nut by hammering on it. Well, when I got the bike, the rear axle was frozen in solid. A few squirts of PB Blaster, and a good whack with a rubber mallet loosened it up enough to take it out. After removing the old, dried grease and cleaning the axle with 600 grit paper, it all worked smoothly. I cleaned up the threads on the axle with a ¾ file, then got a temporary nut at a hardware store. It is quite difficult to find a new 18mm castle nut, but I have one on order now. In the mean time, a plain 18mm nut holds things where they belong.

With the rear wheel done, I moved on to the front wheel. Same story here, but before installing it, I mounted the front fender and brake hose brackets. Everything was then tightened to the correct torque specs.

 Next on the list was to install the wiring back on the bike. This was somewhat of a pain, as the harness is pretty stiff up front, but a few quietly uttered cuss words later it was where it belongs. Tidying everything up inside the headlight bucket was more of a challenge, and time consuming.  I took a Q-tip and some dielectric grease, and lubed all connectors as well. Since I’m going with lower handlebars, I have an extra length of wiring that has to be tucked away in there as well. I’m running out of room, but I hope it will work in the end.

 Up to this point, I was making some good progress. Feeling motivated, I decided to tackle the airbox and carburetors. Oh my, oh my, oh my! Between not having enough room to get a finger anywhere, and not wanting to scratch the newly painted frame, it took me over an hour to get it in there. Despite lubing the boots, the carburetor assembly would not go into the cylinder boots, and when it finally did, the airbox boots were all over the place. I tried sliding the airbox over, but for the life of me I could not get all four boots to seat properly. There was always one that ended up crooked. I ended up taking the carburetors off the cylinders again, attaching the airbox boots, and then sliding the whole thing forward. Some cussing and heavy breathing later, it was finally in. What an awful design!

I also installed a new chain. This one has a masterlink, so no more taking the swingarm off to work on it.


After installing the exhaust, I decided I wanted to hear the engine. Well, the truth is, I wanted to rebuild the front brakes, only to discover that the master cylinder cover is beyond repair. I’ll have to order a new one. So, with the brakes being a no-go, I decided to hear the engine.

I installed the tank, connected the fuel line, and poured in a little bit of gas. And here the issues begun.

Number 2 carb started leaking from the drain nipple. Hmm…I cleaned and reassembled the carburetors before taking the bike apart, and I remember testing them on the bike. At that time, there were no leaks.
So, after making sure the drain screw was all the way in, I took the crew out again, and polished the cone-shaped tip. A little oil on the O-ring, and it went back together. No leak since – let’s hope it stays that way.

Then, I started the engine. Cylinders 2,3, and 4 ran fine, while cylinder 1 only came on with RPMs above 2k. I checked gas delivery and spark, and could not find anything wrong. I also know that the carburetors are clean, and there are no vacuum leaks in the boots. Well, this is one puzzle I’ll have to investigate later.

 

CB750F Project: Brake Saga Continues

As stated in the previous post, I started working on rebuilding the brakes on my CB. There has been a slight delay, however, as the original OEM pistons were not up to the job. Yes, I could have probably polished them and called it a day, nevertheless, I don't like doing things half-ass.

And this is where I ran into a small problem: The rear OEM piston appears to be discontinued by Honda, and all the kits available on-line show three pistons of the same size - 38mm diameter by 35mm length. The rear piston, however, measures 38mm diameter and 41mm length. There were some pistons of the proper size available via Google.co.uk, but as with anything "reasonably" priced these days, the country of origin is likely China. Forgive my snobbery, but when given the choice, I'd rather not rely on Chinese made cast brake pistons.

The solution? I asked around, and ultimately found a machine shop willing to work with me on creating a set of brake pistons to match the OEM size. Not only these will be the correct length, but I could also specify the material. So, instead of ordering the questionable quality pistons on-line, I chose to order a set of stainless steel pistons made locally.  The availability of stainless steel makes for a product that will last much longer than the traditionally chrome-plated pistons which are prone to pitting. 

I always believed in supporting the local community whenever possible, and this was the perfect occasion.

The machinist had the new pistons ready for me the day after I ordered them. Frankly speaking, I spent more time searching for a set online, and driving around numerous parts stores, than it took to have them made.

And here they are, right next to the pitted OEM ones.

CB750F Project: part VIII

Brake time!

When I first brought the bike home, the rear brake was completely stuck. The Previous owner drained all fluid from the reservoir, and took the bleeder out of the caliper. That's about it. He neither investigated further, nor attempted to fix the issue.

A week after I ordered two rebuilt kits the parts finally came, and I was able to get to the bottom of it. I started on the rear brake, as that was the one in the worst shape.

This is what 30 year old brakes hide under the dust seals

Ah...nothing like a broken circlip to make this easier. It was locked in place with rust, and took some heavy pounding to move.

And a little surprise underneath the flange. I swear, this fluid looks like the original, 30-year old fill.

Well, about 30 minutes of playing with a Dremmel and some brake cleaner, and things looked much better.

Time to get the new piston, seals, and spring in.

And voila...final assembly. I lubed the seals with fresh brake fluid prior to installation.

With the master cylinder rebuilt, I was able to use the hydraulic force to push the stuck piston out of the caliper. Except a hardened seal and some decent corrosion inside, the caliper looks good and can be reused. the piston, however, has some decent-size pitting. I'll have to look for a replacement.

Tomorrow I'll tackle the front.