Topic: '78 CB750K Project #1 - Cafe-like Racer-ish Bike

[Stoli]

It's time to start the project thread.  I've been lurking for months and have made some decent progress on my build so my first few posts will come quick to get up to speed.

I doubt I will have anything original to say here as I am very new to all of this and most of my new found knowledge has been seeded from elsewhere in this forum. I thought that I might be able to contribute by listing some of my experiences along the way.

I decided to take a break from restoring old arcade games this winter and try my hand at fixing up an old motorcycle. Last August, I aquired a couple of '78 CB750Ks that were both stockers. One of them was seized, lots of rust on the wheels and frame and had 8K on the odometer. The second one had an engine that turned over, much less rust, more miles, but in overall better condition. I decided to start with the seized bike and for cost reasons decided it would be much cheaper to go the cafe route since the exhaust was rotted through, the tank had a big dent where knee dents would go (it fell over I suspect) , and the rims and fenders were in tough shape. Still have not decided what I will do with the second bike (stock or cafe), but that is next winter's project so I have some time.

Here it is:



First up, the engine ....

[Stoli]

I have some pics of the engine rebuild but they pretty much look like everyone elses, so I'll skip to the final product. Well, almost (I think the only thing I did after I took this pic was polish the sprocket cover). Turns out the engine was seized due to some moisture creeping in to cylinders 1 & 4 (through the exhaust valves). Other than the corroded rings, the rest of the engine looked great and I suspect the bike was well maintained for the first 8K. New gaskets, seals, rings, studs, cam chain as well as a cylinder hone and some valve lapping and I think it's good to go. Obviously lots of cleaning as well.



Lessons learned:

- As a minimum, I would suggest the Honda Shop Manual, Parts Manual, and this thread: http://forums.sohc4.net/index.php?topic=29364.0

- I went with the CycleX Gasket and seal set. Seemed like decent quality although I'm sure you get what you pay for when it comes to the gaskets. I did have to trim the head gasket a tiny bit around some of the cylinder stud holes to get things to line up. You will probably find that it isn't a complete seal set as well - was missing a few o-rings. If you want to know which ones, just ask and I will dig through my notes.

- The kick starter retainer pin is a #$%* to get out but I finally leveraged it out with a pair of wire cutters.

- Also, I doubt you will get the 4 screws that secure the countershaft holder without having to drill. Even with an impact driver, I think I only got 1 of them out without drilling. You will need to remove the countershaft holder to disassemble the crankcase properly. 

- Don't try to use a torque wrench on the 6mm flange bolts that secure the cylinder head. Torque the stud nuts of course, but use a 1/4" ratchet on the 6mm bolts and tighten by feel.

- The APE cylinder studs have a "long" threaded end and a "short" threaded end. On the 750 engines, the long threaded end goes in to the case. The long threaded end is a little larger so you might think you are cross threading on the way in (you won't be able to go past a turn or two by hand) but if you double check that the stud is going in straight after a turn or so and have a little faith, it will go in the rest of the way with an installer tool or double nut. It took me a few hours of googling to get up enough courage to get past the first turn.

 

[Stoli]

Engine Removal & Installation:

This actually might be an original thought that I came up with on my own. At least I didn't see it in any of the other engine removal posts on this forum but I'm sure someone else has done it before me. I didn't use it to remove the engine but the install worked like a champ and I'm sure it will work just as well for my next removal.





Using the very cheap Harbor Freight 750lb Engine Stand with 2 feet of 2" black pipe from Home Depot, I was able to suspend the engine while I guided it into the frame which was held up by the very cheap Harbor Freight Motorcycle lift. You can't see it in the pics, but I drilled a hole through the pipe (about 2" from the end) and mounted an eye bolt (also from HD) that the orange ratcheting straps (also from HD) are secured to. The eye bolt was a bit long, so I cut off the part that stuck out past the nut so it wouldn't hit the frame. One man operation, took about 20 minutes from start to finish.

[theofam]

Good to see another 78K on the forum!  The work thusfar looks top notch!

Great idea on the engine install. I have the same Harbor Freight engine stand. Can you upload a pic of the eye bolt on the 2" pipe? I may have to copy you.

[toytuff]

Subscribed.

tt

[fendersrule]

Great progress. I'm so happy to see that hideous seat gone.

[toytuff]

Great progress. I'm so happy to see that hideous seat gone.

They were very comfey.

tt

[Stoli]

Wheel Relacing & Truing:



I thought this would be harder than it was since I had never done it before. Turns out it really wasn't too bad. Just takes some time and patience like everyone says.

Lessons learned:

- This thread was the most helpful: http://forums.sohc4.net/index.php?topic=368

- I opted to go with a stand that costs a little more than the one that Harbor Freight sells based on the bad reviews. The one I used is a "Tusk" and cost about 70 bucks online somewhere. I did go with the HF gauges and magnetic bases however.

- The one problem I noticed, which is probably true of all of the lower priced stands, is that the cone shaped collar that is used to center each side of the wheel hub on the truing rod will get slightly offset as you tighten the little hex bolt that secures the collar to the rod. To avoid this problem, I essentially increased the diameter of the rod (in the area where the coned shape collars were) by wrapping the rod with a layer or two of aluminum speed tape. This gave the cone shaped collar a nice secure fit around the rod so when I tightened the hex bolt, the collar wasn't pushed off center.

- SPOKES!!  - I went with the Buchanan Stainless Steel spokes (sort of expensive but very well made). Here's the rub though - if you can't find a premade kit for your bike on their web site, don't trust them to make you ones that fit by emailing or calling them. Send them one of the inner and one of your outer spokes from your original wheel so they can duplicate them. In the case of my '78 CB750, they had a premade set for the front wheel but not for the rear (the rear rim size of the 750 changed over the years so they don't have a premade set for the rear). I called and gave them the hub and rim size and they sent me a set.  If I had done my homework, I could have avoided a hassle (others had gone before me) but I wound up with rear spokes that did not fit correctly. Eventually they made new ones that were perfect, but it cost me some shipping and about 2 weeks of time. The front set fit perfectly the first time. Buchanan had great service and I actually talked to one the Buchanan brothers when I called back, but for some reason they will try to make up a set of spokes without asking for the samples even though they know they might not fit correctly.

- Save yourself some money and polish them yourself on a buffing wheel with some rouge. Takes very little time and the polished SS spokes look fantastic.

[Stoli]

Good to see another 78K on the forum!  The work thusfar looks top notch!

Great idea on the engine install. I have the same Harbor Freight engine stand. Can you upload a pic of the eye bolt on the 2" pipe? I may have to copy you.

Here you go. I cut off the excess eye bolt thread flush with the top of the nut after installing it. In the pic, the nut is wrapped with electrical tape to make sure it didn't scratch the frame in case of contact during installation. I opted for the black pipe which was a few bucks more per foot than the regular galvy but supposedly stronger.

With one strap, I secured one end to the eye bolt, then routed it down and around the alternator cover, back up through the eye bolt and then down around the points cover then back up through the eye bolt then down around the rear of the case then back up through the eye bolt and secured the strap. I routed a second strap around the top of the valve cover, down around the case bolt just below the oil filter opening and then back over the valve cover and hooked it to the bottom rear of the case. The first strap held the engine up while the second secured it from tipping forward due to the heavier front end. I found that hanging it so the intake boots were at the same level as the pipe was a good position to keep the pipe away from the top of the bike frame.

[edhaeuser]

Awesome idea for the engine install!!!  Engine looks really good too!


Ed

[Stoli]

Knee Dents -

Hard choice, made much easier by the fact that there was a big dent in the tank already, presumably from the bike tipping over at some point. I was worried about the bottom edge of the tank getting pulled up and in by the hammering so I cut out a couple pieces of wood that followed the contour of the bottom of the tank and placed the tank on top of them while I hammered. That little flange along the bottom of the tank hugged the wood so it kept it's shape. Say what you will about the 77-78 CB750s but I really like the big tank. Sort of bad ass. I think I am going to have a problem with the clubmans though. In order for them to clear the tank, I need to rotate them up and forward and me thinks its a little too far forward.



Here is the tank in it's current state, primed but not quite ready. I still have another afternoon of bondo and fill primer work to get it right before painting. I plan on painting it gloss black, which will show every little ding, I'm sure. This has been my first experience with bondo. Man that stuff hardens fast. Wish I could play with it a little longer before if starts firming up.

[toytuff]

I must admit, you do fabulous work!

That tank is sick! Again, four 

tt

[Stoli]

Thanks tt. My goal is to spend as much time in my workshop as possible so as to avoid talking to my wife. That seems to help with the quality of the work. Never in a rush.

[Vinhead1957]

Great work and I usually lock the door

[iron_worker]

The engine is lookin real nice.

IW

[SOHC4 Cafe Racer Fan]

Great job on the knee dents.

[Blitzburgh207]

Wow this is looking sweet! Clean build man, you do good work.  I love the knee dents on this tank - I've never seen that before.  I have a spare 77 tank w/ a dent in it that might be getting some knee dents soon! 

[Stoli]

Wow this is looking sweet! Clean build man, you do good work.  I love the knee dents on this tank - I've never seen that before.  I have a spare 77 tank w/ a dent in it that might be getting some knee dents soon! 

It gets a little difficult where the 77/78 tank has that contour line that runs front to back along the top of each side because the metal is obviously stronger where it has been pre-bent, but the end result of actually changing that line in the tank looks pretty cool I think. As long as you get each side symmetric and close to where you like it, there is nothing a little bondo can't fix. I had to keep telling myself that as I was pounding away.

[Stoli]

Gauges -

Several lessons learned here. If you want to save and reuse your rings, I suggest you cut them and then epoxy or jbweld or whatever they do to get them back on. Or,  if you want to do it without cutting the rings, then go search Youtube for the videos by "lecramrettub" who came up with a great technique using a large hose clamp and some other jigs to get the ring off and back on without damaging it too much.

I opened mine as per the video and it worked well, but I got lazy when it was time to close them back up and tried using some duck-billed pliers (as suggested elsewhere on the interweb) to recrimp the ring and man did I #$%* it up. So, that's why you see the Joker Machine flanges. They set me back a Benjamin but what the heck, it's only money and you can't take it with you. I'm already about a grand over my budget on this project so what's another hundred bucks. I might be making up some different faces anyways so this way it is real easy to open them back up.

[toytuff]

Budget? Yeah, never could keep them.

The CBX just about put the house in jeopardy! 

tt

[theofam]

Thanks for the pic of the 2" tube w/ eye bolt. I may use that method for my upcoming engine install. The knee dents look cool. I'm not sure I've seen a 77/78 tank with them. It's gonna be a sweet ride - keep the updates coming!

[Blitzburgh207]

Too rich for my blood but damn do they look nice 

[Stoli]

Gauge Lighting:

Another thread somewhere in this forum turned me on to LED halo lighting. Fairly inexpensive, and since I was opening the gauges to replace the faces with my own, I figured I would check them out.



Hooking the LEDs up straight to 12V was way too bright but I found that placing a 1K Ohm resister in series with each "halo" resulted in just about the right brightness. I came up with a circuit that has a few light sensors and should result in an automatic brightness adjustment that is off during the day, goes full bright at dusk and dims to the current level (with the 1K resistor) when it gets dark. These pics are kind of blurry but you get the idea.

 

[Stoli]

Too rich for my blood ...

That's what I was thinking before I screwed up the bezel ring. I will say that the Joker Machine flanges are very well made. I thought they would be plastic but they are metal (aluminum I think).

[Stoli]

Finally got started on the seat and rear fender of my cafe-like racer-ish resurrection of the '78. Not sure what I am doing or where I am going with this but I think it might work. I thought I would try to use the original seat pan but needed to get rid of the passenger part so I cut it off. Then I molded a fender out of some pink foam from Home Depot, and coated it with a thin layer of Bondo and finally some filler primer. From what I've been told and read, it is preferable to create a female mold for fiberglass, but I think I'll try version 1 with this male mold and see how it turns out. I will cut the bottom edge of the fender along that black line so it follows the contour of the rear wheel.



Tried to match the lines on the gas tank. This perspective makes the fender look much bigger than it actually is.