Topic: A Noob's Build of a '78 CB750k

[Boulevard_beck]

Is that seat & pad from Lengendary Motorcycles?

Kinda, mrrch. It's the "Legendary Motorcycles Bug-eye Cafe Racer Seat" but I got it from Dime City with the pad and snap cover: http://goo.gl/QXEl4 It's plastic, but it's pretty stiff and feels strong. I'm using the mounting kit for it, too.

And by the way, your bike is amazing. What a great job you've done. The gold engine is just perfect!

[Boulevard_beck]

After the weekend trying to get the bike running, I finally did. But the insanely difficult start made me give in and order a full carb rebuild kit and sync gauges. It's not going to a shop to get done this time. I'm doing it myself, no matter how long or how much beer it takes.

[Boulevard_beck]

I spent the past weekend working mainly on my Suzuki M50 because the rear shaft drive needed to be replaced. I also had a bit of a rats nest under the seat due to my numerous little accessories, so I cleaned up the electrical and routed some accessories to a new fuse panel.







But, let's get back to the Honda. This week was mainly just some little things here and there. I checked the spark plug gaps and adjusted them to be 0.030" as my Clymer's manual suggested.



I checked the valve covers and adjusted all of them. Wow, they were REALLY off. Then I read a bit more about how to adjust them and found out that you actually adjust the valves that are loose when you're on Top Dead Center for 1-4 and 2-3. Which meant of course that I had completely adjusted them in the opposite way. So, I spent another evening adjusting them correctly. At this point, I wasn't even surprised that I did that.





I also got a chance to wire up the rear headlight into the seat. I used one of those quick release clip things for the wires so that it's easier to remove the seat when I need to. There really wasn't much to the brake light...drilled holes and hooked up wires. I enjoy my ability to not screw up electrical work...seems to be one of the few things I get correct on the first try









My new tires came in the mail...and so did my tire irons to remove and install the new tires all by myself. However, given my track record for making mistakes, and the seriousness of tire installation quality, I decided to take my tires to a shop to get the work done. Time Machine Motorsports here in Edmonton charged me about $30 per tire and did a great job.





The last thing I did was install the steering damper. It turned out that this was a lot easier than I thought. Along with the damper, I ordered a little brace that attached to the frame of the bike pretty well. There was a little bit of space, but I just added a few wraps of extra rim strip that I had, and that made for a tight grip for the mounting bracket. The lower triple tree had a bolt that holds a little curved piece of metal that keeps the wiring harness in place. I simply removed the bolt and used a similar, but longer, bolt in its place in order to install the other end of the steering damper. I know that those dampers are really for serious racing bikes, but they just look so cool, and the whole setup was less than $100.









And that's it. I'm now waiting on my complete carb rebuild kit and carb sync gauges. Once I receive those, I'll clean the carbs, rebuild them, sync them and I should be about 95% done my build for now. I have loads more work that I want to eventually do (paint, new starter button bracket, and more) but, the bike will be rideable. And I intend to do some riding.

[Mossy21]

Very nice work.   I to live in Canada.... Newfoundland.

[CB_Jeff]

Very nice!
Have you mounted the seat yet?
I am interested to know what you think about the mounting kit from Dime City.... I am thinking about using it as my plan to use the stock seat pan, hinges and plunger is not going to work out as my cafe seat is too narrow.

[Boulevard_beck]

I haven't mounted it yet, but I've gone through all of the instructions and cut the mounting pieces to the right size, drilled all of the holes and positioned everything up. The universal mounting bracket is the type of thing that once it goes on, I really don't want to have to remove it becuase it'll take a good 30 minutes to get on and off given the tiny area to work with and get a wrench in. Might not make sense, but I'll be sure to take some pics to explain when the time comes - in the next 2 weeks.

That's for the mounting bracket. For the seat itself, the instructions have you screwing into the bracket, but I'm not going to do that. I have some pretty strong industrial Velcro that I'm going to use so I can just rip the seat off and on.

The solution from Dime City seems to work ok, but if I had the ability to create a seat pan and properly mount up a seat, I would have gone that route.

[Boulevard_beck]

Last night I spent some time completing the wiring on my speedo indicator lights. A few of the wires threw me off, so I might post a quick cheat sheet on how I hooked up the Dime City speedo to the OEM wiring and got everything working.

The big achievement was building my own 2 into 1 diode. The OEM indicator cluster had two lights - one for each turn signal. The Dime City speedo only has one turn signal indicator light. So, I needed to connect both signal lights together for the indicator to work regardless of which signal was blinking. The purpose of the 2 into 1 diode is to allow the left and right signal lights to be connected together, without actually "shorting" each other out. The diode only allows power to flow up to the indicator light, not back across to the other signal light...otherwise you'd hit left signal and all four lights would blink.

You can buy a 2 into 1 diode for about $7, but you can just make your own for about $2 in parts and 30 minutes of effort like I did. I simply soldered together two 3 AMP diodes...



And then added some heat shrink wrapping...



And finally heat shrink wrapped the entire thing all into one nice tidy unit.



Then, I hooked up the two leads to each of the turn signal light power wires, and the single lead to the speedo indicator light and it works like a charm! Saved myself a couple bucks and about a week of shipping cost/time to Canada.

[castillor]

I have the same bike as you and plan to go the same route with the speedo. I already have the arrow style turn signals. Did you have any trouble wiring up the signals and them working properly the first time?

[brandEn]

Just found your build. Your doing a great job on documenting it. I love build threads like this. Subscribed.
Oh yea, thank for the podcasts. I listen to Joe Rogans podcast when Im in the garage.

[Boulevard_beck]

For the signal wiring, it was pretty straight forward - just positive and negative wires to hook up. 

For the rear lights, I hooked up the ground wire right to the frame where I mounted them and hooked up the positive to the correct wire in the rear of the bike (Blue for Right, Orange for Left).



For the front lights, I cut the OEM lights and disconnected the wires from inside the headlight bucket. Then I just hooked up the new lights in the exact same way: positives to their respective wires (Blue for Right, Orange for Left) and the ground wires connected to the Green ground wires attached to the bolts that are mounted inside the headlight bucket on the left and right.



The OEM front signal lights had a third wire coming out of them which was either Blue with White Stripe or Orange with White Stripe. Those two wires went up to the OEM indicator lights. Now that I'm using an aftermarket indicator light, those two wires are just sitting empty in the headlight bucket.

[Boulevard_beck]

Oh! One important thing to keep in mind is that I did need to purchase a modern flasher unit. The reason is that the new signal lights have less resistance in them. The original flasher had a safety feature where if one of the signal lights would burn out (causing less resistance) then the flasher would stop working. Therefore, with these new signal lights, the stock flasher always thought that something was wrong and just lit up the lights solidly.

I bought a new 2 prong flasher and removed the old square one from it's little rubber holder. Then I "gently" forced the new round one into the rubber holder and re-mounted it up. Worked just fine. Who said you can't put a round peg into a square hole?!?

[Boulevard_beck]

And since I'm on my lunch break at work, here's the quick cheet sheet for anyone who purchases either the black (http://goo.gl/W4tpi) or the white (http://goo.gl/EsTBT) speedometers with the indicator lights from Dime City Cycles.



There's a couple of things to keep in mind. First, the neutral switch light gets connected to any switched power wire (Black) and it gets connected to the single switched ground wire that is all alone in the headlight bucket (Green/Red). This threw me off at first.

Second, for the signal lights, the 2 into 1 diode gets connected to the signal light power wires as noted above if you are using aftermarket signal lights. You'll end up having two wires left over in the headlight bucket (Blue/White and Orange/White) that are doing nothing. However, if you're using the OEM lights, then I "think" you'll need to connect the 2 into 1 diode to those striped wires instead. I haven't verified this, though.

If you see something that I got wrong, let me know and I'll update this.

[castillor]

Thank you for all the wonderful info.

[matt s]

Hi - I just found your build thread.  I just have to say that starter switch is the business!  Nice work!

[Boulevard_beck]

Not much of an update since I'm preparing for a 5 day bike trip through the mountains on my Suzuki M50. The Honda sits waiting for me to rebuild the carbs and get to the end of this serious hard starting issue. I'm pretty sure the accelerator jets are not working and that's causing the bulk of the issue.

I did do one tiny piece of work, though - I installed the stopper for the center stand. Since I have MAC 4-2 pipes, the center stand was hitting the chain. VintageCB750 hooked me up with a super cheap stopper and it bolted right in with the rear hub stopper mover thing. It's late...I'm tired...you know the rod I'm talking about.

Geez, that center stand looks bad. I'll need to clean and paint it one day.

I'm thinking that the bike will be in tip top shape in about 2 weeks. 3 weeks max, if I end up breaking something during my carb rebuild. So...3 weeks, then.

And, thanks for the comments castillor and Matt. Matt, it looks like your build is a heck of a lot more work than mine, that's for sure! Did you ever get rid of that weird looking seat? Never seen one quite that...umm...unique.

[Boulevard_beck]

The past couple weeks have been pret busy. No time for working on my Honda because I was preparing for a nice 5 day trip through the Canadian Rockies on my other bike. The trip was a load of fun and I rode some of the best roads that I've ever been on. Here's a few pics and then we'll get right back into the rebuild...









Now that I'm back home, I've had some time to work on the CB750k. I received some wire wrap in the mail to help clean up my speedo and tach wires that were exposed and just didn't look very nice.





I also picked up some orange colored wrap to see how it would look on the spark plug wires. It's a little different, but it just might work.



And then came the big carb rebuild job. It took me the entire weekend to get everything back together. It sure was daunting going into it, but now that I've done it, it didn't seem too hard at all.

I started by taking the entire thing apart and sorting it to be soaked in some simple green to help loosen everything up. I organized everything into its own container and soaked them for 1 hour. Then I gave them a good scrub with a toothbrush and left it all in the garage to dry over night. I finished at 1am, so I didn't want to get out the air compressor to dry everything - although I should have. I spent about 3 hours total cleaning.











The next day, I found the carbs to have a pretty bad film of calcium (I think) all over. I cleaned it up as best I could and just charged ahead hoping things would be ok. It took quite a while to get it all back together. Lots of looking at diagrams, lots of putting it half together and then finding something wrong so I had to take part of it apart again. The kits were super simple to install, though. I had 4 o-rings left over in each kit that I didn't end up using because they were not required on my carbs. Getting those springs back in the right place was probably the toughest part. This all took a good 3-4 hours to do and I just left the idle jets at 1.5 turns out like the Clymer's manual says.

Today, I reinstalled the newly rebuilt carbs. I've done this so many times now, it seriously only takes 10 minutes to completely reinstall these things and hook up the throttle and choke cables. My little choke holder screw is starting to strip though...I'll have to pick up a new one some time.

If you remember like I do, my bike was nearly impossible to start up previously. After reinstalling everything, it started up on the second try...so very nice to hear that. However, it was still running a little rough.

Determined to get this right, I began by syncing the carbs. The sync gauges fit great and were a breeze to set up. With the right tools (carb sync gauge and proper adjuster screw driver) syncing the carbs was very, very easy to do.



Carb #2 cannot be adjusted, so you adjust #1, #3 and #4 all to match the levels of the second carb. Everything was completely out of whack when I started. It's no wonder this bike ran like crap.











After about 10 minutes of fiddling around with the idle adjuster screw and each of the individual adjustment bolt/screws, I got them pretty much aligned.



Once I got everything together, I cleaned up the shop and decided to go for a ride. Nothing major, just a quick trip around the block to see how everything feels after 2 months of working on it. It was my first ride since pretty much when I bought the bike and it feels like a whole new bike!

A few things to note. I'm going to leave the pods on for a while to see how poorly they operate. I want to determine for myself how different the pods are versus the air box. Second, those clubman bars are the most uncomfortable motorcycle bars I've ever used. They look cool, but jeez...after only 10 minutes of riding, my wrist was starting to feel it. I have a 3 hour ride planned to go camping this weekend, so we'll see how that goes with this bike. 

And a quick note about the Dime City universal seat: it's ok, but it's not all that great. It'll last for the summer, but come next year, I'll be looking for a new one for sure. It fits...but not perfectly. It was a #$%* to install and it's not all that secure on there since I just used velcro to stick it to the mounting bracket. I like the look, but I think it's going to end up being a temporary seat.

I'm also leaking some milky liquid...most likely oil. And that's never good. It's leaking oil out of the exhaust pipe on the right side. So, the oil is obviously being shot out of the engine thought one of the exhaust exits, which I'm thinking that means i have a faulty ring??? It's happening in either #3 or #4. For the next little while, I'm just going to live with it. I've been without for too long, time to do some riding. I'll just keep an eye on the oil level and eventually take it in to get fixed, because tackling the engine is too much for me, I think.



I want to wrap the pipes, but I'm not sure if I will until I get the oil leak fixed. Something tells me that oil soaking into my exhaust wrap wouldn't be a good idea. In the weeks ahead, I need to fabricate a license plate mount thing and I might make a better ignition button bracket. There's also half a dozen little things I might clean up, like the cable routing and clutch engaging late.

I also want to do a nice little photo-shoot of the bike some afternoon. There's some interesting construction yards, industrial areas, graffiti covered places and miscellaneous locations that would look cool for some pics that I want to check out. But, for the rest of the summer though, I think I'm just going to enjoy it. The bike is a little rough around the edges, but we'll call the Noob's Build v1.0
complete for now.

v2.0 of A Noob's Build of a 1978 CB750k is planning to have:
- Oil leak fixed by replacing rings
- Purchase a new gas tank
- Possibly purchase a new seat
- Possibly relocate electronics under seat
- Purchase new side covers with 750Four badge
- Make a logo of a cappuccino with foam blowing off
- Paint tank, side covers, seat white or grey with a blue strip offset to the left
- Relocate ignition to side of bike somewhere
- Install a new front brake master cylinder

The updates will be slow and very irregular for the rest of the summer. Version 2.0 will probably begin sometime next year or maybe over the winter. Until then, I've got a new bike to get acquainted with.

[TrueSpin]

I know it's kinda late in the game for someone to point this out but I wanted to make sure you're aware. The metal plate that you took off the rear sprocket and decided not to reuse - I strongly recommend putting it back on. It's specifically designed do exactly one thing - keep the chain out of the axle if it comes off the sprocket. Without that plate, the chain will end up in the axle and lock up the wheel most likely.
If you choose to continue without it, that's your decision, just putting it out there.

As far as the rest of the build, I like pretty much everything else you've done except the seat. Never been a fan of short round tails.

Great looking bikes, great to see someone who rides a ton and will enjoy the bike, rather than just slapping it together to make a buck.

[Boulevard_beck]

Thanks for pointing that out - I hadn't realized what it was for. I'll make sure I add that to the list of things I still want to get done in the next couple weeks before I officially stop working on it for the summer.

[Boulevard_beck]

Took the bike out for a nice long shakedown ride tonight in the pouring rain to see how everything is holding up.

The biggest issue I'm having now is what looks to be unburned fuel leaking out of either the #3 or #4 cylinder into the exhaust. I had thought it was oil at first, but in the rain I could see that it was fuel being spilled onto the street when I was at a red light.

Also, the oil light came on and my oil pressure gauge was reading quite higher than expected, so I think the unburned fuel is getting into the oil, maybe. I'll have to check that out.

I'll take a look at the spark plugs and do the usual spark on the engine thing to make sure the coils are still good - that's what I suspect the issue is. And, I'll need to do an oil change now, I suppose.

Also, the clutch is slipping a bit and I've got it adjusted all the way out, but it still only grabs at the very last second. So, I'll take a look inside the clutch cable area down by the engine to see if I can adjust it there a bit. Otherwise, I might need to install new clutch plates??

On the plus side, there was a huge rainbow after all that rain tonight!

[Boulevard_beck]

Well, I'm not sure what the issue is. I checked the spark plugs and they're both sparking when I press the ignition button. I'm at a bit of a loss now as to why there would be unburned fuel shooting out of #3 when I'm getting spark.

[Boulevard_beck]

I think I solved my problem. Two of them actually. And, the solution is unconfirmed just yet...

The first problem - shooting gas out of exhaust #3 - I think has been solved by taking the carbs apart. In fact, I'm now convinced that all motorcycle problems can be fixed by taking the carbs apart. Blinkers not blinking...carbs are your issue.

But for me, the issue was that I had put the carbs back together incorrectly. The #3 carb cylinder thing that holds the long needle jet was put back in reversed. One side has a raised side and the other is just flat. So, I'm guessing that the raised side cause a constant vacuum pulling up too much fuel all the time.

The attached pic shows the difference between #3 on the left and #4 on the right. From this angle, you'll see that the flat side of the cylinder is facing the wrong direction. I also ended up playing around with the mixture screw, so now I'll need to re-sync them.

I haven't had a chance to sync them up again because it's too late now and I'm going camping tomorrow. So, I'll see how things are running on Monday maybe.

And as a side note, l fixed some accelerator pump issues I was having. I found that the PO did not have an O-ring on the float bowl with the pump. Since he never had one, I never replaced it when I rebuilt everything. I only found out when I decided to shoot carb cleaner up the vent to see where the fluid would go...turns out that it went right out of the carb because there was no seal.

I'll report back soon, when I get a chance to sync everything up and take it for another spin.

[harisuluv]

Dang! Epic journey so far. Question though I thought that you had the carbs back from being rebuilt in the first few posts, but then you rebuilt them yourself?

[Boulevard_beck]

Thanks harisuluv. And yes, I had a shop rebuild the carbs with some kits I had that basically only included the needle and float bowl gasket. I expected the shop to magically fix everything and give me back pristine carbs, but in the end i just ended up getting what i told them to do - install these little kits i had. They didn't touch the accelerator jets And only barely cleaned the carbs in general (no soaking or sonic cleaning). I never explicitly asked for this, but I kinda expected them to recommend whatever needed to be done...not to return them still inoperable.

The shop did an ok job, but it didn't fix any of my issues, so I decided to stop being scared of carbs and learn to do it myself. I can honestly say that rebuilding the carbs has been the most gratifying part of my build yet!

[Boulevard_beck]

Just a quick update on the final touches to the build. The carbs are working pretty well now and there is no longer any unburned fuel leaking out of the exhaust pipe. Funny how one little simple thing caused such a big mess. I'm glad I figured out the issue though...such a great feeling of achievement to solve that problem on my own.

Unfortunately, my accelerator jets might not be working properly - they don't squirt. I'll need to double check that the following things are working correctly: o-ring isn't blocking tubes, mickey mouse ears on diaphragm isn't closed, check ball is working/smooth, jet holes aren't clogged. I'll get to it whenever I have time, though. My performance is suffering a bit, but it's not bad enough to make me want to fix it immediately.

In addition to that, I got some more work done. First up is a license plate bracket that I fabricated out of some heating duct metal that I found at Home Depot for $2. I cut it to size, drilled some holes and bent it into the approximate shape that I was going for. It's been going for a good week now and seems to be working great.



Second is that I've now basically installed the Dime City universal seat bracket and seat for good. I've finished measuring and cutting all the bits and it's on there pretty good now. The seat itself is held to the bracket by some Velcro attached to a piece of wood. The wood was required because of the height of the bolts not allowing the seat to come into contact with the bracket itself. It's not very sturdy, but when riding, I barely notice that it's not perfect. Here's some pics of the seat install.













I also started wrapping the exhaust pipes. I say "started" because I actually ran out of wrap half way through, haha. I used 2" width, 50' length of tan colored wrap and it was enough to only do one side of my 4-2 exhaust. I picked up another pack and I'll try to finish the job this weekend.

The steps I followed to wrap them are: soak wrap in water, remove exhaust pipes, clean pipes, start wrapping at the rear (not at the engine side), wrapped around twice at beginning and end, used metal ties to secure the ends temporarily, used metal hose clamps to secure ends when complete. All in all, I like the look that I'm getting - a very "garage build" style.

[xnoahx]

Looking good.  I just picked up a 78k also and plan to cafe it.  I need to get mine running first though.  I cant believe you spent so much before you got the carbs dialed in and the bike running.  Looks all taken care of now though.  Keep it up.