Topic: 1976 cb750F Noob building a cafe

[unamusedd]

Well this is a thread on my 1976 cb750f cafe racer build. I've owned the bike about a month now. Someone attempted to start a cafe build but it was nowhere near what I had imagined my bike to be. The mods done by PO are

• Kerker 4to1 exhaust
• Pod filters(no name brand)
• Batwing bars?(I believe that what they're called)
• Cafe Seat
• And I assume modified or aftermarket tank
• LED rear turn signals (that did not work)
• Metal side covers to hide the atrocious wiring back there

Here she is the day I bought her


 Just a quick heads up this is my first motorcycle project. I've done lots of auto work but the most I have ever done on a bike is replace the plastics. When it comes to bikes I'm a total noob. I specifically bought this bike because I wanted to have a running bike to start off with but also something I could customize as my own. I wanted something I could enjoy for the rest of the season before I tore into her.

After going to take a look at her I was not aware of how big and heavy she was. In all honesty I was intimidated to say the least. She was leaking a bit of oil, had no working turn signals, no brake light and had a small exhaust leak. All minor things I thought I could fix relatively quickly. She was delivered to my home and I immediately wanted to take her for a quick spin around the block. Didn't even make it a 2 feet without stalling out. In my mind i thought this was my fault, started her back up and she stalled out again. Extremely frustrated I tried to figure out what was wrong. I removed the seat to take a look at the battery and found the terminal for the ground cable was to big for the battery bolt and that the terminal was only held on by two strands of wire. Immediately I removed the cable and replaced the connector. She fired right up and I was finally able to take her for a quick spin. She ran somewhat rough but I thought this was normal of a bike from 1976.

Attempting to repair a few things and get her running a bit better I ordered a universal taillight, spark plugs, oil and filter and got myself a matching helmet  . I added a taillight and rewired the led turn signals that were on it. I gapped and replaced the plugs without a problem. I remember the PO telling me that to do an oil change on this bike you only remove the drain plug on the oil tank and drain from there. This to me was extremely strange especially considering there is a drain plug on the motor and its accessible. So I proceeded to drain the oil from the pan and realized why he didn't want me touching that drain plug. The drain plug had been stripped and held in with what I assume to be RTV. I quickly looked up the price on a new pan and could not believe the cost. I then looked up the specs and found that advanced sells a Spark plug repair kit with the same thread size. Its basically like a timesert. For 30$ it was worth it. I bought a new plug and successfully repaired my drain plug. I thought to myself this is going pretty damn well. While I was repairing the plug I had to remove the exhaust so I sanded down any rust/paint and sprayed the whole thing in high temp black. I started her up and she ran so much better but still had a flat spot in the low to mid range.

Fixing drain plug and painting exhaust


I enjoyed her for about two weeks until I started to look up parts and ordering them. A few other issues I found were:

• Front brake squeaked and felt spongy
• Brake lines had small cracks in them although they did hold pressure
• Battery seemed old and would barely hold a charge
• Blinkers wouldn't work due to stock flasher (right blinker wouldn't work from what I suspect to be the switch)

So I found cognito moto (huge shout out to them for wonderful parts and quick shipping!) had some parts that I wanted and the rest I found scattered across the web.

I ordered

• LED turn signal and brake light strip(Cognito Moto)
• Oil Tank (Cognito Moto)
• Electronics tray(Cognito Moto)
• Stainless steel brake hoses in black
• New Turn signal/headlight switch
• EBC Front rotor and pads
• 7" Headlight with integrated LED turn signals
• Shorai battery
• LED Flasher (universal)

and began to disassemble and modify. My goal was to free up some space in the "triangle" under the seat.

Heres a photo beginning to redo the wiring to fit in the shallow tray along with adding inline fuses to remove the old fuse block. You can also see where I planned on hiding the battery.


Tray almost done(regulator mounted underneath for cooling purposes), oil tank mounted, and temporary battery box. you can also see the nice little breather I added(that started to smoke after the bike was warmed up)


The seat also needed to be cut to hide the battery in and to add my LED strip. I also added silicone to any close points to the terminals as a precaution.



Slowly but surely she was coming along. I painted the bare metal and added the LED strip



I assembled her back up since my battery box needed to get welded and the only way over there was to ride her.


I rode her to have the box welded and realized the breather smoked only when the bike had warmed up. She also still didn't run the way I thought she should. I figured why not run some sea foam through her to try and clean the carbs out. I emptied the bowls, sprayed carb cleaner wherever I could and proceeded to remove the tank and make a sea foam funnel to run the engine entirely on sea foam.


I also replaced the plugs once again after I was done with my sea foam treatment. Reinstalled gas tank and she ran much better once I burned through all the sea foam. Got the engine hot and so far no more smoke from breather. However the bike still had a flat spot. I would twist the throttle and she would bog between 2500-3500. I would leave the choke slightly on and she was about 80% better. She must have been running lean. I was terrified of touching these carbs. They look intimidating but I figured its now or never. I removed the carbs and realized she still had stock jetting! From what I read this is a no no with pods and exhaust. I was hoping to find one or two clogged jets but not this. The carbs actually look brand new inside ( I guess the PO maintained them well or the sea foam actually worked)


Now my carbs are out and I'm looking for the best rebuild kits (for the best price) and a carb syncing tool. I'm also on the fence about electronic ignition. The build is on hold for now until more parts get here. Brakes will probably be next since I have most of the parts here for that. I do wish I had ridden a properly tuned cb750 so I have something to compare mine to.

If anyone has any questions or suggestions please let me know!

[Jerry Rxman Griffin aka MuthaF'er]

Compare the Keyster parts to your stock. I junked the Keyster needles and screws and re-used the stock since they were not identical.

[Retro Rocket]

I see the PO cut off the stock rear shock mounts from the frame and made new oner lower down, I wonder why he did that..?..

[SOHC4 Cafe Racer Fan]

I see the PO cut off the stock rear shock mounts from the frame and made new oner lower down, I wonder why he did that..?..

Just noticed that, too. Odd. It forces you to use stiffer shocks with less travel.

[Retro Rocket]

I see the PO cut off the stock rear shock mounts from the frame and made new oner lower down, I wonder why he did that..?..

Just noticed that, too. Odd. It forces you to use stiffer shocks with less travel.

I knew something seemed wrong back there but I could not figure it out. This is my first build and these bikes are still very foreign to me. Should I have the shock mounts put in the stock position? The only reason I can see is to get the rear a bit higher off the ground.

I think there would be a couple of benefits to having the stock shock mounts, first would be better suspension travel as Don mentioned above as well as a better range of shock options, not many bike that size running small shocks like that and most of the smaller shocks on the market aren't all that good..

[calj737]

When I pulled the carbs they were in the 2nd position, now I'm debating if I should put it in the 1st.

If you're lean, move them to the 3rd position. 1st would make them VERY lean. The lower the clip (toward the taper) the higher the needle is raised, the richer the mixture.

[Jerry Rxman Griffin aka MuthaF'er]

ie forget the needle position as everyone seems to  get confused, from the top or the bottom. Just raise them sonsa#$%*es UP.

[Retro Rocket]

[calj737]

regarding your carbs: Expect that the previous owner mucked with them, and mucked with them good. Your jets and needles may no longer be stock and could very well be aftermarket units. This means ALL bets are off on their tuning setup.

If you found the needle in the first position from the bottom, that would be the most rich. If you are lean as a result of that configuration, then you have the wrong jets in your bike, and/or your air screws are completely whacked.

Please remove the needles and take a picture of them. There should also be a # stamped on them (super small writing) and on the jets. These numbers are important to verify (pilot and mains). But if your needles are not stock, then their taper is completely different and you need to find replacements, else you'll be chasing your tail for along while.

[unamusedd]

Perfect, thank you!

[Jerry Rxman Griffin aka MuthaF'er]

 Has it been noted that the middle needle position is stock for our carbs?!

[unamusedd]

Has it been noted that the middle needle position is stock for our carbs?!

I was under the impression that the 76f used the second position. I was going by hondachopper carb specs.

[unamusedd]

Well I got my new carb boots along with my new gauges. While the carbs were out I changed the needle position. The needle is now letting the most amount of fuel in. Its running a lot better but theres still a very small flat spot which I think is from the slow jet. I think size #42 would fix this issue. Also need to order new pod filters since mine are beat. The other thing I noticed is I don't have a rubber mount where my tank bolts to the frame. It worries me that I don't have anything there to absorb some vibration. Perhaps I can fab something up if not I'll try and order the stock rubber.

[unamusedd]

Still making lots of progress on it but I haven't had the time to post. The new gauges are in, front brake lines are in, swapped the lever on my front master cylinder, new front rotor and front pads, new headlight, turn signal switch and almost all of the wiring is done upfront. I was able to take her for a ride and she feels so much better with the carbs redone. Here are some pics.











The few things I still need to fix include, getting the rear turn signals to work. They worked with the old switch and new led flasher but now they don't so I need to trace that down. Oil light doesn't work which I think its the pressure sensor. Still need to fix a tiny flat spot which I think upping the jet to a 42 should do the trick. Last is to weld the strut mounts where they're supposed to go. DolaMike was kind enough to send me the stock ones so I'm in the process of trimming it down. I also need to order new pod filters, which I don't know what size it is and my vernier caliper is lost in the mail somewhere (if someone knows the size and a good site to get the pod filters from please let me know) and I want an LED bulb in the headlight. Debating on wheels, tires and exhaust but thats last on my list. I'm really just flustered by the rear turn signals, if anyone has any ideas I would really appreciate it



Almost forgot, I want some quality clip ons so I need to start searching for that and maybe some rear sets also.

[unamusedd]

It looks like my plans have changed. I'm all over the place with this bike. Originally I was going to go with a 17x4.25 in the rear and a 18x3.50 in the front but an opportunity to buy an 05 R6 for dirt cheap came up and since I was planning on doing a front end swap eventually I figured might as well do it now. I brought the R6 home last night and started tearing her apart today. Im going to be sending the lower tree out to cognito moto tomorrow for a new stem and eventually will buy the hub they offer to run a spoked front wheel. I just need to part the rest of the R6 out before I can spend anymore money on this bike.

Unfortunately I already replaced the front brakes on the cb750 with EBC pads and rotors. I also replaced the lines with stainless steel lines and modified the aftermarket lever to fit my stock master cylinder. A little annoying doing all that work and spending that money for nothing but this new front end will hopefully perform better.

[DohcBikes]

I see the PO cut off the stock rear shock mounts from the frame and made new oner lower down, I wonder why he did that..?..

Because he jumped on the brat bandwagon and fabricated a flat tail section which reduced his tire clearance to almost nothing and forced him to make another mistake trying to fix it.

Did the R6 run?

[unamusedd]

Well I got back from vacation Tuesday and was able to get a lot done yesterday. Cognito moto pressed in my new stem while I was away which made the swap very easy to do. I'm almost done with the front end swap but these next few days I'm going to be busy so I won't be able to work on the bike for a week or two. Heres some current shots of it.

[unamusedd]

Well I told myself I wasn't going to buy anymore parts until I sold the 3/4 of the R6 I had left and I was finally able to do that so I got a few things done on the bike. I replaced and timed the ignition and the advancer unit, had the shock mounts welded in place and ordered a Cognito Moto wide rear wheel. For the rear wheel I unlaced my hub, well actually cut it out and painted it black.

[unamusedd]

White I wait for my new rear wheel I decided to paint the tank and seat. I used VHT engine paint which hopefully will withstand small gas spills.

[jaycox]

I can tell you that it won't stand up to gas, sorry.  Buy some 2k clear in a can it works awesome and you can get it in matte if that's what you are looking for.  I used Eastwood matte and its pretty good.

[unamusedd]

I can tell you that it won't stand up to gas, sorry.  Buy some 2k clear in a can it works awesome and you can get it in matte if that's what you are looking for.  I used Eastwood matte and its pretty good.

I was afraid of that. I read mixed reviews about it holding up to gas spills. I think at this point I'm going to find a body shop that can do a satin black for relatively low cost.

[s10hornet]

Perfect, thank you!

I too have a 76 cb750f and had many headaches with the carbs.  Here's what finally worked.  I went to 115 mains, needle in middle position.  But that's not all.
I tried the pods, K&N's (not cheap).  IN the end what got the best results was going back to the stock airbox with a K&N filter.  Bike runs great and the plugs are perfect.

I know a lot of people like the looks of the pods but the truth is your bike needs the airbox.  And if you buy the cheapo Emgo pods you'll never get it to perform.

[unamusedd]

Perfect, thank you!

I too have a 76 cb750f and had many headaches with the carbs.  Here's what finally worked.  I went to 115 mains, needle in middle position.  But that's not all.
I tried the pods, K&N's (not cheap).  IN the end what got the best results was going back to the stock airbox with a K&N filter.  Bike runs great and the plugs are perfect.

I know a lot of people like the looks of the pods but the truth is your bike needs the airbox.  And if you buy the cheapo Emgo pods you'll never get it to perform.

I was able to fine tune the carbs with the uni pods and I'm happy with the results. I didn't have the stock airbox when I bought the bike just the cheap pods, but the Uni's seem much better quality. I do however want Devins new airbox which will probably be my next mod once my wheels arrive.

[SOHC4 Cafe Racer Fan]

Let us know how well it works.

[unamusedd]

So an opportunity came up and I took it. Picked up this 1982 cb750k on Saturday and rode her home about 100 miles.

After I warmed up I started taking her apart to see what I had to work with.

Not sure which direction to go with it or keep it stock but its fun to have a cb to ride while my wheels get here.