First Project! '78 CB750F

[Gunner]

Hey everyone,
I just thought I'd make a thread to keep me motivated on this new project I just recently bought.

Here she is.

What you see is what I got. All in all the frame looks to be in good shape, a little dirty with some rust here and there but no corrosion. The engine has good compression but that's all I know, I'll address that when the time comes. Other than on the some of the bolts, the enginge has no visible rust. I know I have my work cut out for me! I am starting from scratch as I sold all my tools when I enlisted five years ago, so I'm just buying what I need as I go. With my limited shop experience, the praised CLYMER manual, lots of patience and the good'ol interwebs, this is going to a fun little project. My intension was to make a hardtail bobber out of it but I'm leaning towards a cafe racer now. It's probably safe to say that I'll be on this site quite a bit looking for pointers on, well, everything!

 

[losttravlyr]

yep you have a lot of work ahead of you,but creating something from a little of nothing is the most fun to me. did it come with a title and what plans for the front end and wheels?

as for tools,,harbor freight is a wonderful place that is affordable for the home builder. like everything imported nowadays there are diffrent levels of qaulity,but the cheap extended warranty on power tools and the lifetime on hand tools plus so much variety makes it my go to place now. i dont even hardly ever use my craftsman,matco and snap on stuff anymore.

 

[Gunner]

I have the title in hand, that's the main reason I bought it. I've been through the trouble of getting a title and I never want to deal with that again. As far as the wheels go I've been looking at putting together my own, I have a good friend who knows all about it. I'm still up in the air for the fron end, I'm currently on the hunt for original parts but who knows what I'll find. Any suggestions on good aftermarket sites or in general would be appreciated!

 

[Travis]

If you're going to use a lot of original CB750 parts, you might want to try looking for a good no-title donor bike for cheap. Those big parts, and all the little ones can really nickle and dime you. If you plan to put on a different front end, wheels, tank, gauges, redo the wiring, etc, well then it looks like you're off to a good start! Have fun with the project!

 

[Gunner]

I just finished taking the motor out, now its time for some cleaning and sanding!


I have the motor sitting on a stand. I imagine it will be a week or two until I get to the motor so I'm looking for a better way to store it, any suggestions?

 

[Gunner]

Thanks Travis! I JUST found a deal today, this guy has this project that has gone horribly wrong. Everything but the frame itself is apparently in good condition, carbs included to! $300

We'll see..

I was getting the grime off of my frame today and I hit my first (of I'm sure many) bump in this long road. There's a small crack running parallel with the frame, the pics below are showing its size and location.

The plan was to cut that piece out and weld on another, any suggestions? I've played with JB Weld before but I'm not really sure about using it on the frame.

 

[dirtdigger]

The crack is actually a split caused by water getting into the tube and it freezing which splits the tube. I have seen this before. If you do cut and replace the tube make sure to use solid plugs inside the joints to help strengthen the joint...dont just butt weld the tubing together. Possibly find a welding shop that would tackle the job and have them also tig weld it. Other option and maybe best option would be to get another titled frame. I wouldn't consider JB weld to really be a structural fix, more of a hole filler for something like this.

 

[Gunner]

Thank you dirtdigger that was the route I was going to take. I have a friend who's a certified welder, he should be able to do it. How likely is the frame going to warp, should I have the motor installed when the welding is being done? I imaging I'll be able to use part of the frame from the bike I'm picking up here soon as the replacement, I'll have to do some web surfing for the plugs.

 

[dirtdigger]

Once you cut the tube just machine some solid stock to a snug fit in the tube. Before cutting I would cut some metal to the exact size or just a hair more then the distance between the motor mounts and clamp or tack weld them in place to hold the distance so it doesn't close up when welding Ideally you would mount in a frame jig or temporarily spot weld the frame to a accurate flat metal bench then cut the tube out and weld in place.

 

[Gunner]

Sounds good, I'll see what route my buddy is comfortable going with. Thank you.

 

[motogtp]

Parts

Hey everyone,
I just thought I'd make a thread to keep me motivated on this new project I just recently bought.

Here she is.
View attachment 3708
What you see is what I got. All in all the frame looks to be in good shape, a little dirty with some rust here and there but no corrosion. The engine has good compression but that's all I know, I'll address that when the time comes. Other than on the some of the bolts, the enginge has no visible rust. I know I have my work cut out for me! I am starting from scratch as I sold all my tools when I enlisted five years ago, so I'm just buying what I need as I go. With my limited shop experience, the praised CLYMER manual, lots of patience and the good'ol interwebs, this is going to a fun little project. My intension was to make a hardtail bobber out of it but I'm leaning towards a cafe racer now. It's probably safe to say that I'll be on this site quite a bit looking for pointers on, well, everything!

I may have some new and used parts you are interested in. Off my '78 Super Sport that has 6,000 miles on it. New - Cycle X air filters; AlloyBoltz upper, lower & oil pan SST bolts. Used - chain guard, taillight and mounting, shocks, headlight bucket reflectors, metal café racer seat pan, seat bracket, upper air box, chrome Super Sport tank emblem, etc. New parts retail for $100, I would take $150 for the lot.

 

[Gunner]

Thanks MotoGTP I'll keep that in mind! I think I'll be focusing on this parts bike I just got. The guy I bought all this from was in a giving mood I suppose, all of this for $300 seems like a good deal to me!!

I guess he decided to practice welding on something he'll be going 75mph on, the frame is garbage but there are quite a few gems here.

 

[dirtdigger]

That frame looks looks scary What are you going to do with the spare motor? If you decide to sell it or part it out let me know...also that set of carbs. I am always on the lookout for spare motor and carb parts.

 

[Gunner]

I'll definitely keep you in mind. As of right now I'll be holding on to most of it until I finish my bike. I really need to go through that box and figure out what I can use.

 

[dirtdigger]

Do you know which motor you are going to run? Any work going into the motor you are going to run? They are both black motors but that doesn't mean both or either of them are F2 motors. Motor numbers on the case and I can tell you what you have. Also see what the casting number is on the head...in the center of the top fin on the intake side there should be a 3 digit number cast into the head. 410 is the big valve F2 head. It helps to know what motors you have when it comes to finding parts and part fitment.

 

[Gunner]

I'll get back to you on the motor heads.
As for the motor itself they both start off with CB750FE-31 and I believe end with 3. I was under the impression that it wasn't an F2, sure hope you can confirm this, HA! I've been looking for '78 CB750F parts. I'll be running the motor I initially got, it is way better upkept than the one I just got. Maybe down the road that will be a rebuild project.

 

[Gunner]

Just looked at the Heads and both are 410 so I'll keep that in mind if I rebuild that extra motor. Now the Carbs that acquired are "keyholes" and to my understanding that is what the '77 & '78 models used, am I correct in thinking they are compatible with my motor?

 

[dirtdigger]

410 means you have F2 motors. There are different keyhole carbs but as long as you have the correct boots between the head and carbs. The F2 gets a little more tricky once you start getting into internal parts replacement just because they have some specific parts for them. They also had some issues with the valve train so keep an eye on it.

 

[Gunner]

Will do, thank you! I'll be taking the motor apart just to ensure everything is clean and good to go. What type of specifi replacement parts are we talking here, gaskets and pistons? I'm hoping between the two motors I should be able to get somethign running!

 

[dirtdigger]

Cylinder, cylinder head, pistons, rings, valves, retainers, springs are specific to the F2. Gaskets should all work. Be forewarned new rings are discontinued and very hard to find for the F2 and should be replaced anytime the cylinder is removed.