Topic: '78 CB750F Cafe Project Log (Minnesota)

[nick55555]

Greetings fellow SOHCers. I have recently acquired a 1978 CB750F for $300 and plan on converting it into an old school cafe racer. Right now I have a bare frame and a box (nay... several boxes) full of parts. I hope to build a cafe similar to Carpy's award winning '75 Cafe (just google "cafe racer" if you don't know what I am referring to), and the following is my high-level vision:

- Get a café style seat to mock up on frame. [I will probably go with Carpy's 'Dunstall' seat. I was thinking about an airtech, but Carpy's seats are so sweet and about the same price.]

- Make necessary modifications to frame for seat fitting, then send the frame to the powdercoaters.

- Pop the head off the engine. [I believe I read somewhere on the forum that the super sport heads were somewhat problematic. What should I look for/replace when I have the head off to avoid future troubles? Valve guides? Also; who uses phillips screws to attach a valve cover?!?!?!! Is there a good way to get these off if they are really tight? I have tried at them a bit, but really want to avoid stripping them if at all possible, so I didn't go past the point of no return. Advice?]

- Repaint the engine, and any other parts that need it, a low-gloss or flat black.
- Carbs are currently being given a thorough cleaning, new bowl seals and float needles.
- a very simplified rewiring (ie: high/low headlight, turn signals, electric start and brake light)
- (?) lower the front end by introducing some clip-ons
- (?) lower the rear end with 11" shocks (or find some CB900 shocks & use blocks or a new swingarm. Does anyone know if there are any better semi-compatible swing arms that can be fitted with minimal modification??}
- replace fasteners with hex-head ones
- new tires
- new gauge faces
- new headlight mount
- rebuild brake calipers (all three of 'em)
- general clean up and replace anything that needs replacing


I am sure I am forgetting some things, but that is the basic idea. I don't really plan on doing any modifications to the engine, other than getting it dialed in properly. Since this is my first bike and I think the 750 will keep me satisfied for a while.

I will post new pics as I go along and HOPE to have it roadworthy by spring. Please let me know your thoughts and especially any advice as far as things I should pay attention to during my rebuild.

Cheers,
-Nick in Minnesota
(if you are in the Twin Cities, let me know. It would be nice to have a local network of enthusiasts.)


Pick up day:



Teardown:



Currently down to the frame:






PS - I am not planning on using a lot of the original parts for this rebuild, so let me know if you are interested in any of them.

[legendary]

Nick,
         I was reading your post and saying, "If this said 1976 instead of 1978, it could be my build."

I took my engine out on 12/23/07 and I have the frame stripped like yours. I paid $350 for my project.

I was surprised similarities...then I saw the pics... you and I have exactly the same make and model engine stand! Cardboard over Plywood, '07 model.

I was inspired by Carpy's site,  and like you I'm leaning toward the dunstall.  I live in the other twin cities, "Scranton Wilkes-Barre, PA"  I am planning on a complete motor rebuild, new electrical etc.  Just like MN.... here in PA we have the crappy weather on our side.

I'll probably spend a bunch of money working on that stuff...burn out on the project and sell all my stuff for pennies-on-th-dollar on this forum.

But I am enjoying the heck out of it!

Good luck with yours!

Steve

[UnCrash]

Greetings Nick,

It's great to see someone digging into a 78F.  I have the same bike, so will be paying special attention to your project.

Those phillips head screws will come out reasonably with an impact driver,  go down to your local Sears and find one.  You can't go wrong with them and a little PB Blaster.  If you're going all the way with the girl it would be best to replace them with Allen head ones.

Best of luck with your build.

[KB02]

- Pop the head off the engine. [I believe I read somewhere on the forum that the super sport heads were somewhat problematic. What should I look for/replace when I have the head off to avoid future troubles? Valve guides? Also; who uses phillips screws to attach a valve cover?!?!?!! Is there a good way to get these off if they are really tight? I have tried at them a bit, but really want to avoid stripping them if at all possible, so I didn't go past the point of no return. Advice?]

As for the head, send a PM to MRieck. He's a member here on the boards (and one heck of a guy) and knows these heads inside and out. He'll set you right.

As for the screws, Uncrash nailed it. Get an impact driver and get 'em out! Replace wit a nice set of Allen head screws.

ps - I can't seem to get your "Pick-Up day" picture to load.

[nick55555]

@ legendary: Haha, the '07 cardboard over plywood works great for now... but if we ever decide to check out the lower half, we may have to upgrade  . Sounds like we are two peas in a pod; I have a tendency to throw a bunch of time and $ into something and then loose inspiration... but Carpy replied to an email that I sent him the other day and included enough youtube links to make an anchor chain (Carpy's sayings are priceless!!)... which should keep me going. Keep in touch about your progress!

@UnCrash: good idea with the impact! I am heading out to the hangar in a bit here to give it a shot (and I plan on replacing just about everything that had a phillips head with a hex head).

@KB02: Thanks for the reference and the heads-up on the "pick up day" picture; it ought to be working now.


Just placed an order to partsnmore for some stuff (clip-ons, oil filters, caliper rebuild kit, and some air filters), so I can start making some FORWARD progress now.

Thanks for the advices, and I'll keep yall posted!!

[KB02]

@KB02: Thanks for the reference and the heads-up on the "pick up day" picture; it ought to be working now.

Yup. Now I see it.    Good looking project. Keep us up to date!!

[mikedialect]

welcome to the F club.

[TwoTired]

Welcome to the club.  Hope you have fun with your project. The F models have a bad reputation for valve guide wear and blowing oil through the guide seals.  Many (it seems) have replaced the heads with the K model counterparts of similar years.  I'm from the get-it-running-first-and-see-what-it-needs before dismantling camp. I was told by a Honda mechanic, that most were repaired under warranty with hardened valve guides, and later models were delivered with the upgrade, so the bad rep wasn't universally true.

 My 78 F project is going the other way...back to stock.
Mine still needs the headlight, fork ear headlight mounts with rubber grommets, and all the turn signals/mounts.  If your front fender is un-dented with good chrome, I could use that too.
PM me if you have an interest in selling those parts.

Cheers,

[bgfootball67]

Good luck with your project!  Carpy helped breath new life in my old CB 750, by giving me some cool ideas.  While I could not afford to send him the bike to finish, it got the wheels turning.  I eventually pick up a Benji's tank combo about a year ago, of Benji's Cafe Racers.  It has been a fun project, looking to get everything finished before too long.  Check out BCR as I think he is doing an SS...

Again, good luck and have fun!

[mikedialect]

I should also add that I'm in MN (just outside DT MPLS) if you're close.....

[nick55555]

TwoTired: I am also from the "don't fix it if it ain't broke" camp, but right now it is moreso because I actually want to have it running by spring... there is always next winter to attend to the next batch of maintenence/upgrades.

mike: good to see another minnesotan! I work in fridley and have the bike in stillwater. What projects do you have going on? Let me know if you ever need a hand (these 750 engines are HEAVY!!!)

Legendary: great thread that you and smack doodle have going with the 750 rebuild... may need that next winter.


Ok a few more things I forgot to mention, mixed in with some questions:

I want to go to 4-1 exhaust (black with the canister). What do you know or what have you heard about the quality and price of the available stuff? (ie: Mac, and some other ones that I don't reacall). I would like to find something for less than $300, but I don't want to cheap out too much either (I have learned my lesson about going the cheapest possible route).

Carpy said something about putting a seat that he made specially for F's on his website in a few days. Depending on how sweet it is I will either go with that or his Dunstall seat within a week to mock up on the frame.

I have the forks all apart now for cleaning... Should I replace all the seals and dust boots while I am at it, or just leave them alone if they look okay? Any other fork/suspension tips?

Oh, I also just discovered www.z1enterprises.com.... WOW!! I will most definitely be getting some stuff from them (bar end mirrors, aftermarket headlight ears, etc etc.). Any other favorite part websites out there that I may not heard of (I have heard of bikebarn, partsnmore, bikebandit, crc, z1...)?

Does anyone have any tips on painting the engine? I don't plan on going into it too far this winter (ie: valve cover off to check things out and MAYBE head if I need to), but would like it to look better in the spring as it is a bit scratched up. Can I just seal it all up, sand blast and paint it???

Thanks UnCrash & KB02 for the impact tip... all but one or two of those pesky screws remain... letting them sit in some penetrant while I get a larger diameter air compressor hose.

I guess that is about it for now. Just waiting on the seat to fit it up and then send stuff off to the powedercoaters.... I will try to make the next post more impressive guys!!

-Nick

[Aaron J Williams]

It takes a determined person to take his first bike apart before riding it but it will work out fine if you get it back together before pothole season. I'm about 40 miles north of you on the other side of the river and I would love to go riding when you get it dialed in!

[nick55555]

That sounds like a plan to me Mr. Williams!

I LOVE THIS FORUM!!! I have a bare frame and a riding partner...


Okay, electrical question....

Does the generator put out AC? That is really the only explanation that I can think of, but I wonder why Honda didn't make it a DC generator. What is/are the outputs directly from the generator (probably varies with RPM)? Are there any good electrical/rewiring posts or resources that anyone knows of? Anyone on this board that has a lot of experience with it so when the time comes I know who to ask.

I have a wiring diagram for my bike (well, I am pretty sure it is the right one) and am just trying to get an idea of the absolutely essential components of the electrical system. As mentioned previously I will be keeping it minimal with LED turn signals (and flasher relays) and tail/brake light(brake light switch), high/low beam, electronic ignition, gauge backlights... am I forgetting something essential? It doesn't seem too difficult (since I am an engineer and have done my fair share of playing around with electronics).

Oh, and before I send my frame off to the coaters: Is there anything else I should address (as far as frame modification) besides the seat fit (which I will probably be fitting straight to the frame, ie: grind off the hinge studs)??


Thanks again everyone!

[mikedialect]

make sure you mind the vin plate before you send it

[mgmuellner]

Another MN boy, welcome.

Before the coaters - well a few things.  Do you know how all items will mount, such as the tank. Are you going with a stock tank, or do you have to work out mounting locations?  Some folks fix the welds & insure a full weld on each gauset (even spellcheck didnt fix that one).  Are you keeping the side covers & other little bits?  If not you will probably want to grind off the tabs for these.  Some also cut off either the central stand or the side stand.


Forks - I'd replace the seals at least & look at the boots.  It's not expensive & just like a lot of other little things, it'll save you a few swear words down the road.

[TwoTired]

Should I replace all the seals and dust boots while I am at it, or just leave them alone if they look okay?

I'd replace the seals if you have the forks broken down.  The dust boots are optional, if they look good, are dark shiny and resilient then you can reuse them.

Does the generator put out AC? That is really the only explanation that I can think of, but I wonder why Honda didn't make it a DC generator. What is/are the outputs directly from the generator (probably varies with RPM)? Are there any good electrical/rewiring posts or resources that anyone knows of? Anyone on this board that has a lot of experience with it so when the time comes I know who to ask.

I have a wiring diagram for my bike (well, I am pretty sure it is the right one) and am just trying to get an idea of the absolutely essential components of the electrical system. As mentioned previously I will be keeping it minimal with LED turn signals (and flasher relays) and tail/brake light(brake light switch), high/low beam, electronic ignition, gauge backlights... am I forgetting something essential? It doesn't seem too difficult (since I am an engineer and have done my fair share of playing around with electronics).

Yes, the alternator puts out 3 phase AC and requires six diodes (a Rectifier) to rectify it into DC.  It also has an excited field coil to make the electromagnetic field.  So, it also needs a "regulator" to reduce the alternator power output when the battery is at full charge.

I suspect there is an alternator instead of a generator for the same reasons the entire automotive industry switched in the 60s.  DC generators have a commutator and brushes which wear faster and fail sooner than devices with slip rings or, in Honda's, case no brushes at all.
Autos switched over, in part, due to better charging at idle speeds. But, don't be expecting large charge currents for Honda's 750 alternator at idle.  With the stock electrical load, it didn't charge the battery much at all below 1500-2000 RPM.  If you are making electrical mods, you should probably make up a power budget, particularly if you are adding high watt devices like searchlight style headlamps, or a riding suit heater, low ohm coils, etc.

You going to do away with the neutral and clutch safety devices that prevent the starter from working at inopportune times?  Are you doing away with the starter?  What part of the stock electrical harness to you think you won't need?

Cheers,

[SD750F]

Great to see another MN rider in the area (I'm in Sioux Falls SD) also with the same bike I have. Should keep tabs on each other and plan a ride in  Mankato in the spring...

Scott

[mireparo]

Nick:
I wish I subscribed to this forum before I began my '77 CB750F project. However, I'm a diehard do it yourselfer who doesn't like asking for help.  Doesn't seem to payoff, but I'm not quite ready to give up yet. Your going about it the right way. I ended up rebuilding my top end three times and I think it is blowing oil through valve guide seals like TwoTired mentioned, because it's not dripping but it is drinking.
Here's an abbreviated run down of my (first full) project which is almost finished, minus some cosmetics and tuning (maybe a new engine or at least a head ).
Tear down to frame.
Sand blast and powder coat frame.
Rebuild front fork, carburetors, calipers and master cylinders.
A lot of cleaning.
Newly rebuilt head on Ebay from a matching F motor. A steal for 125 bucks, but not worth it. They did a poor job cleaning up the lapping compound and it probably should have had all new valves and valve guides and ground (but thats just off the top of my amateur head), so I tore it apart relapped it and cleaned it well.
FYI I split my case sandblasted and painted my motor with PJ1's case paint. Not bad for a rattle can.
Added many new and used parts (my bike is semi-stock)
I went with Mac's 4into1 exhaust. I think it looks cool and sounds okay. I'd like to make is sound like a 400f with stock 4into1 w/ pods, but have no idea how.



I runs pretty well, I'm still having a little trouble tuning the carbs for pods and after market exhaust.
I believe I've 125 mains and the needle all the way up. You can only use 1/2 to 3/4 throttle till its past 5 grand though. (I'll starting my own thread for that and other difficulties)
I think my next project will be a Cafe and I might just pass my crazy ideas through the forums before wasting my money this time.

It's great to see so many posts from the Twin city area.
Happy building,
Micah
 

[nick55555]

Cool to read these stories. You are from the Twin Cities as well? We may have us a regular Japanese bike club on our hands.

Regarding the needles; is there an easy way to get them out? How did you go about it? I got an extra set of carbs with the bike that I have been using as a reference, and I can't even figure out how to get them out of there easily (actually... at all). I am imagining that, since I am also going with pods, I will need to make some adjustments while tuning and it would be nice not to have to pull the carbs off to do so.

I am still hanging up on the seat! I really want to order Carpy's set up, but I am waiting for him to post his latest seat on his site... I got's ants in my pants! I am going to order on Friday regardless of what comes up... it is time to make some more progress!

[nick55555]

TwoTired - I am planning on completely rewiring the bike. I am sure this is going to be at least a partially monumental task, but I think I can get through it with the help of this forum and making sure to use plenty of in-line fuses (at least to begin with). Am I silly to even consider this (I do have some electronics education and experience)? I really just plan on omitting the dummy lights and all the excess wires.

Is there any benefit to an aftermarket rectifier?

I will replace the fork seals as long as the forks are apart. Any need to replace the springs? I think that one of them is a bit shorter than the other, but still within the manual tolerences.

Carpy got back to me about the seat (he has a similar one on Ebay) and I am going to order that tomorrow.

Still working on one last valve cover screw, and I think upgrading to a larger air hose should take care of it. Probably won't bother doing too much more until I get the seat though.

[mireparo]

Nick,
When tunning the carbs (changing jets and adjusting needles) your best bet is to just remove them from the bike each time. I know in and out 50 times!! Make sure they seat well in the rubbers each time.
As far as adjusting the needles, here is what I remeber off the top of my head.
Remove the top cover of each carb.
Unscrew the slide arm, one screw on the shaft which crosses all four carbs.
From here you can lift the slide and disconnect the arm.
Pull the slide out from the carb body.
Down inside the slide there are two small screws which secure the arm to slide and hold the needle down, unscrew these.
Now the needle should come out for adjustment.

[TwoTired]

TwoTired - I am planning on completely rewiring the bike. I am sure this is going to be at least a partially monumental task, but I think I can get through it with the help of this forum and making sure to use plenty of in-line fuses (at least to begin with). Am I silly to even consider this (I do have some electronics education and experience)? I really just plan on omitting the dummy lights and all the excess wires.

Silly can be quite fun!
I like the the way-high strand count of the stock wires.  If you are replacing with "robotic" wire of an equally high strand count, you should be okay.  I also favor using the same color wires as stock simply because wire diagrams already exist for this scheme.  If you use different color wires, then you have to make a special one off schematic for just your bike.  Or, hope you can remember what you did a year or two down the line when the need arises.  Of course, the next owner will have no clue, and you will be cursed in abstentia.

have you counted how many "excess" wire you will be eliminating?

Is there any benefit to an aftermarket rectifier?

Sure.
It's cleaner.
Surface finish likely prettier.
New shiny plug and terminals.
Relieves your burden of monetary bloat.
The seller benefits from sales profit.
The economy is stimulated.

But, unless the one you're replacing has failed in some way, don't expect an after-market rectifier to gain any battery charging advantage.

Cheers,

[tattoo dave]

I have a 78 supersport build underway,and I got the dunstal seat from Carpy,and it is great! He has been very helpful,and supportive! I paid $900 for my bike,it ran strong,but the front end needed an overhaul,and it wasnt looking too good! Good luck with your build!

[gerhed]

Tattoo D,

Can't exactly tell, but paint job looks reminiscent of that on the
Gulf- Porsche 917's of the 60's.
very nice.

gerhed

[tattoo dave]

I did not use the actual paint codes,just went with something close.I wanted something other than the popular "black" cafe. With the supersport having so much black on it already,and not wanting to do a ton of polishing,I think the color really sets it off.