Author Topic: 78 CB750 F SS cafe racer build (Read 28960 times)

deftone · « **on:** February 08, 2008, 07:41:13 pm »

okay so i am a bit of a newb to the cb750 world but i am willing to learn...i picked up a 78 CB750 SS a month or so ago and it was in need of much help...i was given mostly everything in boxes....i have a bunch of questions listed below...so for starters before i get going on making the thing how i want it i decided it to be a good idea to get her up and running....

i first took apart the entire carburator and cleaned the whole thing up....part of the linking arm was rusted so i had a bit of problem getting 2 of the carbs off...but i did it and soaked everything overnight one carb at a time in gunk carb cleaner...put it all back together without buying a rebuild kit just to make sure it would work.....i then did a bench sync as found on this very helpful site and installed the carbs back on the bike (what a pain this was trying to get all 4 boots to seal)

next i had a friend come over and we went through the wiring harness to find out it is in really ruff shape but we were able to jump a few wires(i have no key) and grounds and were able to get it to act like it want to start....we took the starter out and it was kind of stuck so we messed with it for a while and she broke free and started working like a champ....put it back in, gave her same gas, put the headers on (since that is all i have), put some oil in and bingo she fired up....whooohoooo.....the engine sounded pretty good, the bench sync was a good starting point, and after she was warm she even idled nicely....however the transmission does not work...when in neutral the front sprocket sits idle and you can spin it by hand and it moves freely(i do not have the chain on right now)....then i can put it in gear(not using the clutch since i do not have a cable) and get the same situation as in neutral....bummer

so here are my questions:
1-should the frame number and the engine number match?
2-i have not title so which number is the vin number?
3-should i continue getting the bugs worked out of the wiring harness or figure out the transmission first?
4-where do i start on the transmission??
5-where can i get carb rebuild kits for this model (i have seen them for older and newer years but i am having a hard time finding them for this year)
6-do i need a rebuild kit if the carbs are working pretty good?(i still need to tune them obviously)

thanks for the help and here are some pics....
cheers
tone

KB02 · « **Reply #1 on:** February 09, 2008, 05:15:05 am »

That bike is nice and clean looking. Good project machine.

As for your questions:

Quote from: deftone on February 08, 2008, 07:41:13 pm

1-should the frame number and the engine number match?

They do not match, no, but will be close (As in with the same one to ten thousand range). Check out the main page. there is a list of engine and frame numbers to make sure they are of the same year.

Quote from: deftone on February 08, 2008, 07:41:13 pm

2-i have not title so which number is the vin number?

You will find the VIN stamped into the steering neck of the bike. You should also find thi same number in the silver plate that is rivited onto te steering neck.

Quote from: deftone on February 08, 2008, 07:41:13 pm

3-should i continue getting the bugs worked out of the wiring harness or figure out the transmission first?

I'd say play with the tranny first, but this one is really up to you. For the tranny, most likely, you'll be pulling the engine.

Quote from: deftone on February 08, 2008, 07:41:13 pm

4-where do i start on the transmission??

By Pulling the engine.

Actually, pull the engine side covers off of the left side of the bike. Make sure all of that linkage is there and in place. Hopefully that's all it is and you won't have to pull the engine.

Quote from: deftone on February 08, 2008, 07:41:13 pm

5-where can i get carb rebuild kits for this model (i have seen them for older and newer years but i am having a hard time finding them for this year)

I have a 78 as well. I bought my rebuilt kits at my local Honda dealer.

Quote from: deftone on February 08, 2008, 07:41:13 pm

6-do i need a rebuild kit if the carbs are working pretty good?(i still need to tune them obviously)

Well... they say that any time you open up a something with a gasket or seal, you should replace that gasket or seal. If everything is working and you have no leaks, I'd say keep an eye on it. If you see leaks start to form, get some kits an rebuild again.

Hope this helps!!
-Bob
KB02

garretcb750 · « **Reply #2 on:** February 11, 2008, 07:17:05 am »

its good to see another F build... I love these bikes. I will be following your build.

UnCrash · « **Reply #3 on:** February 11, 2008, 07:51:46 am »

It looks like you have some work ahead of you, but your bike's condition looks great.

Paint and wheels look good, so that will save you some work.

I agree with others, get the tranny resolved first and rebuild the carbs if you're running rough later. That will be an easier part of the sorting out you're doing.

Best of luck.

KB02 · « **Reply #4 on:** February 12, 2008, 04:54:26 am »

Almost makes me wonder if the primary chain snapped on the bike...

Don't mean to put alarm where there doesn't need to be, but it's got me to thinking.

deftone · « **Reply #5 on:** February 12, 2008, 02:24:34 pm »

Quote from: KB02 on February 12, 2008, 04:54:26 am

Almost makes me wonder if the primary chain snapped on the bike...

Don't mean to put alarm where there doesn't need to be, but it's got me to thinking.

i am going to rip open the tranny in the next week or so and see what i find....just need to order a clutch cable to help diagnose what is and is not doing...thanks for the feedback guys
cheers
tone

deftone · « **Reply #6 on:** January 29, 2009, 07:57:48 pm »

almost a year after last post i have some progress....decided to go full custom cafe racer....here are a few pics of the progress....carpy seat pan and tail light, vortex clipons digital tach and speedo, shaved top triple, electrics relocated, all new wiring, a few other things

currently finishing up wiring, working on rear sets, exhaust coming, some sort of custom oil tank and cooler, and more

Flying J · « **Reply #7 on:** February 01, 2009, 05:53:12 pm »

How did you do your shaved triple tree. Are you worried about its strength or lack there of? I just finished my rearsets. Pics are on my thread.

BlindJoe · « **Reply #8 on:** February 01, 2009, 07:36:08 pm »

what kind of speedo is that?

mateo tomas · « **Reply #9 on:** February 02, 2009, 12:34:26 am »

looking nice! Do you plan to brace the rear frame since you cut the original off?

andy750 · « **Reply #10 on:** February 02, 2009, 04:46:19 am »

Nice clean front end. More info on the speedo/triple tree please.

cheers
Andy

A Grove · « **Reply #11 on:** February 02, 2009, 01:34:28 pm »

AH speedo looks super trick!!! what is it?!

imamotohead · « **Reply #12 on:** February 02, 2009, 08:25:14 pm »

I'm building a '75 F1 and am using the same Carpy seat. How are you mounting yours?

ASCSurveyor · « **Reply #13 on:** February 03, 2009, 03:53:32 am »

Speedo looks to be a Koso guage. $$$$

captaincrash80 · « **Reply #14 on:** February 03, 2009, 12:33:42 pm »

Yes, more info on the top triples please

deftone · « **Reply #15 on:** February 04, 2009, 04:10:27 pm »

thanks for the compliments....it is a work in progress

************i will address all inquires below************
SPEEDO
the digital speedo is one of these units (Acewell)

http://www.electrosport.com/street/speedometers-series-2700-2800.php

my buddy wired it all up for me and everything works pretty good...we have to mount a bracket of some kind to hold a speedo sensor and then you stick a magnet type thing to the roter...after that it is a matter of calibrating it correctly...

TRIPLE
the triple i had a machine shop friend mill down for me...we did not take too much out and i think the strength should be okay...if it fails it will fail by cracking and i can replace it then...i don't think if it failed anything bad would happen...we'll see

REAR FRAME
that piece of steel everything is mounted to is 5/16" steel and will have continuous welds on each side...pretty sure it will do just fine.....

SEAT MOUNTING
the front will tuck under the tank and i am going to put some foam strips on the frame rail so the fiberglass does not stress...the rear i am going weld a couple small pieces of tubing to the end of the side rails and fashion some dzus clips to secure the rear...of course my fat butt will do the rest....

prince_ruben · « **Reply #16 on:** February 07, 2009, 04:00:12 pm »

About time punk! Keep the pics rolling~

deftone · « **Reply #17 on:** July 24, 2009, 08:25:25 pm »

well here is the latest updates

oil cooler made from a cadillac catera inner cooler

5 spoke wheels taken apart

chopped fender

gas tank dents

deftone · « **Reply #18 on:** July 24, 2009, 08:26:15 pm »

here is the custom oil tank i had made...my buddy dominic hooked it up and we welded mounts on the frame...it turned out incredible and can't wait til i get this bike back together and down the road...got the rearset brackets on as well...we did a pretty cool hidden rear master too...you'll have to wait to see it once it's done though because i didn't take any pics of the mock up

deftone · « **Reply #19 on:** July 24, 2009, 08:27:03 pm »

final mock up before paint and powdercoat

deftone · « **Reply #20 on:** July 24, 2009, 08:27:57 pm »

engine painted with duplicolor low gloss black

got some stuff painted so i can start assembling....trying to get this beast ready for rockerbox in milwaukee next month...going with a metallic old school gold with black accents...the paint job up top will tie in but it's a surprise

Flying J · « **Reply #21 on:** July 24, 2009, 08:30:49 pm »

WOW!!! i have never seen anybody take the comstars apart. Looks cool. Damn you guys and your custom oil tanks. If your going to build 1, build 2 and make your money back. I want one. I cant wait to see the finish on this one.

Zaipai · « **Reply #22 on:** July 24, 2009, 08:59:47 pm »

Wow looking very sweet, can not wait for the final product! Was the gold powercoat or paint?

deftone · « **Reply #23 on:** July 24, 2009, 09:35:16 pm »

thanks for the compliments

i think i could have another tank made if you are serious...it was not cheap though...and you need to weld mounting tabs to the frame...

decided to go with paint because of some rookie welding...i had my painter do some filling to make it look good...you live and learn they say

poomwah · « **Reply #24 on:** July 25, 2009, 05:20:55 pm »

WOW, that is some AMAZING work. I wish I had half of your skill and talent. I can't wait to see the finished bike. I really can't wait to see the hidden master cylinder :]

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Author Topic: 78 CB750 F SS cafe racer build (Read 28960 times)

poomwah