Topic: Zorro's 1978 CB750 K8

[Zorro]

I picked this up bike on ebay for $900.

Here's the day I brought it home...


It came with a brand new battery.  The tires that were on it were brand new.  I figured I got a decent deal on it...thoughts?  Oh, btw...it didn't run when I bought it.

The speedo says it has 2600 miles on it.  It's basically all stock from what I can tell.  Besides for the wealth of information I've gathered on this forum, I'm a rookie when it comes to these bikes.

I plan on making this in to a cafe racer...probably like most on this forum.  Anyway, here are some pics.  I hope to keep this thread going as I make progress.

I have tank emblems that I got on ebay...haven't added them yet.






Some close-ups...

[Zorro]

Like I said earlier, this bike didn't run when I got it.  Owner stated that "it probably needs a carb rebuild".  I tried starting this thing when I got home, and it sputtered a bit and that was it.  I noticed that the carbs were leaking gas all over my driveway.  Time for a teardown.

btw - the previous owner put the fuel line on the air stem on the 2nd carb!

Anyway, here's a few pics of the dirty carbs...
Fresh off the bike...


Bowls...


Top of bowls with floats...






Top of bowls after float removal...

Notice the corrosion of the stem/main jet of the right carb...surprised gas can do this!


Dirty...

[MasterChief750]

two things
the exhaust on it is not off a 78 its off a earlier bike and if you are going to cafe would you sell me your side covers?

ps the 78 rocks there are a few of us on here with 78 projects. make sure you clean out the accelerator pump system. theres a how to on that somewhere it has 2 one way valves in it thaqt need to be free.

[Zorro]

I never tore the carbs completely apart.  I was worried about re-synching them.  I figured that the carbs were synched at one time or another...so I would just leave them as is.

Clean bowls...


Clean floats...



Clean thingy (not sure what this called fuel/air mixing screw lol.)...


As you can see with in the last image, I had a new gasket kit to install.

After all of the cleaning, I put the carbs back on.  After about 5 minutes of trying, it finally started.

It's running a little rough and a buddy, who knows more than me, is coming to take a look at it.

I need to make sure the engine is mechanically sound before I start tearing the whole bike apart.



Top of bowls...


Erosion of main jet area...


With floats...

[Zorro]

two things
the exhaust on it is not off a 78 its off a earlier bike and if you are going to cafe would you sell me your side covers?

No wonder they aren't quite on correctly.  And maybe that's why it's not running well.
As for my side covers...bad news, the left one has 3 broken tabs and the right one has one broken one.  I do plan on selling parts that i don't need...but I need a complete project before I start selling anything.  Sorry.

ps the 78 rocks there are a few of us on here with 78 projects. make sure you clean out the accelerator pump system. theres a how to on that somewhere it has 2 one way valves in it thaqt need to be free.

Accelerator pump?  Is this on the middle left carb?  If so, I tried tearing it a part, but the three screws were so soft I didn't want to strip them.  So, I just soaked the entire set of carbs in cleaner and hoped for the best.

[MasterChief750]

yeah thats it search accelerator pump and some good reads will come up. i reccomend uying a rebuild kit for the acc pump as well as one for your carbs. whenever you decide to sell those covers as long as you have the broken tabs i would buy them.

[Zorro]

yeah thats it search accelerator pump and some good reads will come up. i reccomend uying a rebuild kit for the acc pump as well as one for your carbs. whenever you decide to sell those covers as long as you have the broken tabs i would buy them.

i'm missing one tab on the lower right.  I'll keep you in mind.

I think I'm taking this bike to a carb expert...per the recommendation of my buddy, who's a mechanic.  I'm leaking air out of one, maybe two, of the headers...definitely #1. 

More to come...

[andy750]

Good deal as the pipes are worth a good amount if they are intact.

If you decide to sell the tank (and its not rusty inside) Id be interested in buying it .

Good luck in getting it sorted  - the carb post with the chip/corrosion on it may give you issues.

Andy

[KB02]

two things
the exhaust on it is not off a 78 its off a earlier bike and if you are going to cafe would you sell me your side covers?

ps the 78 rocks there are a few of us on here with 78 projects. make sure you clean out the accelerator pump system. theres a how to on that somewhere it has 2 one way valves in it thaqt need to be free.

That's no the stock speedometer, either. Hence the odd angle and repeated idiot lights.
Nice job on cleaning up those carbs.

[Zorro]

That's no the stock speedometer, either. Hence the odd angle and repeated idiot lights.
Nice job on cleaning up those carbs.

I think this is the stock speedo.  It's at an odd angle because it's missing some screws in the back and it's just sitting in the bracket.  it might not be the original but I saw this exact gauge cluster on ebay.  The guy listed it at a 78 K8 gauge cluster.  Anyway, thanks for the compliment.

[Coyote13]

I hear those pipes are worth their weight in gold....just saying 

Good luck on the build man!

[andy750]

That's no the stock speedometer, either. Hence the odd angle and repeated idiot lights.
Nice job on cleaning up those carbs.

I think this is the stock speedo. 

Its a stock speedo for a 1969/1970 CB750 and definitely not for a 78.

[knowsnothing]

Yes Andy is right.  78s don't have any lights in them.

[MCRider]

Its not a 69/70 but a 71 K1. The lens is recessed. On the 69/70 instrument the lens stood proud of the cover. Valuable to someone trying to restore a K1. Only K series it came on. Recessed lens AND idiot lights.

Definitely not a 78.

[ksmith0034]

I don't need any of your parts as mine is a '71, but I agree with what others have said:  you can sell most of your stock parts to help fund your cafe project.  I took mine down to the frame and have almost nothing left that was original.  Some folks would cringe.  I just take the money and buy what I want for my project.
Can't wait to see your progress!

[Stev-o]

Interested in the stock seat if there are no rips on it.
Just sayin'...

+1 on selling parts to fund the cafe.

[ksmith0034]

Don't forget to take pictures of EVERYTHING - even if you don't know what it is.  These pictures will help you during reassembly (trust me).  Also, if you think you might need it down the road some time then DON'T sell it yet.  You don't want to have to buy anything again!

[ksmith0034]

Anything new to report?

[Zorro]

Anything new to report?

i did some work on saturday.  Got the new Carpy pipes installed (pain in the a$$).  I had the carbs synched.  I'm getting a valve adjustment now.  I want to get it running really well, then continue with the tear down.  I need to take pics with the pipe on it.

[Zorro]

Build update...

Since I couldn't get the bike running really well, I took it to a mechanic.  He said my carb cleaning job was really good...except for the fuel pump.  I couldn't get the 3 screws out so I hoped a soaking was good enough.  He cleaned this for me and replaced my float needles.  Since I had major trouble getting my Carpy 4 into 1 exhaust installed, he offered to help.

After installing the exhaust we installed the carbs and he synched them for me.  We noticed that carb #2 lifter arm was bent or something.  We straightened that out.

After that, the bike was bogging out after 5k rpm.  We did a valve adjustment.  Still having issues in the high rpms.  We did an ignition adjustment.  This has the bike running smooth!  I'm very happy with the work the mechanic did.

Anyway, here are some pics









Now that I know this thing is running and there aren't any engine/transmission issues...I got it going 90mph...I'll be tearing it down during the winter and hopefully making it look cool.

Enjoy.

[Cuts Crooked]

Any issues with jetting the carbs for those pipes? If you are running stock jets with that exhaust you might not be getting the best out of it.

[seaweb11]

Any issues with jetting the carbs for those pipes? If you are running stock jets with that exhaust you might not be getting the best out of it.

My guess is they didn't try different main jets on it.

[Zorro]

Any issues with jetting the carbs for those pipes? If you are running stock jets with that exhaust you might not be getting the best out of it.

No, we used the stock jets.  I'm guessing if i dyno'd it, we'd be able to tell if it were running lean/rich...however, it's not smoking, it fires right up, it runs through the revs without missing/lagging, and idles great.  I want to run pods but the pods I purchased were either too small or so tight we couldn't fit them on the carbs.  However, we didn't try real hard.  My mechanic didn't like my exhaust all that much at first.  He said it grew on him as he was working on it and now likes the sound/look of it.  I'm happy it's running well.  Much better than I had it running.  It starts as easy as my two near-new sportbikes....that's what I like

[lucky]

You have got to get the accelerator pump fixed and when you turn the throttle you should see the spray nozzles spray a stream of fuel into the intake. That thing you had in your hand was a mainjet and mainjet mixer tube.

That pressed in idle jet needs cleaning too - Use a .010 steel guitar string.

[Retro Rocket]

I want to run pods but the pods I purchased were either too small

I know you rookies love the look of pods but i will guarantee  you that if its running well and smooth with the stock airbox then just leave it as it is, pods are mostly crap and will Never perform on a stock bike like the original airbox. Do a search of the forum and see for yourself. Most people only want pods for the look but they are a pain in the butt to tune and will never perform correctly right throughout the rev range, bogging, flat spots and a higher uneven idle are common.
Your speedo is also off an early 69-71 model 754, it may be worth selling on this site and using the money to get a correct replacement, your pipes are also off the 69-75 model K's, depending on the numbers on them, HM3400's for the early models and HM341's for the later 73-76 K's....