Topic: My $75 Supersport Resurection

[What2007]

Well I'm new around here, and new to fours in general, but I thought I'd post here to keep track of my first cb750 project.

I picked this 78 Supersport for $75 last week and am trying to get her back on the road for summertime. Bike is complete. Nothing missing and more importantly, nothing cut or froze.





More progress to come.


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[What2007]

So today was the first day that I could really dig into the bike. I've had the tank soaking in vinegar the past few days and she cleaned out beautifully. You could eat off of the metal inside. New petcock should be in tomorrow.

While the tank was drying I tore in to the carbs. I noticed this though



It looks like it's set up for a push/pull throttle, but I just have a single pull on there, is this correct?

Also, the choke cable doesn't actually engage the choke, it pulls an arm, but the arm doesn't move anything.



After I got everything apart I realized that I was not the first person to open them up, as evident by the oddball float.



Got everything all cleaned out nice and got the carbs back on, a PITA btw, and tried starting it with no luck. It just popped a couple of times, so I think the PO has the firing order all wrong, but the wires that are on there now are junk so I have new coils and wires on the way. Does anyone have a diagram of the proper wire routing/firing order?


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[madmtnmotors]

Holy cow! Nice score! I'll give you $500 for it right now if you want to sell...


Wiring diagrams can be found here:

http://www.sohc4.net/cb750k-manuals/

[SOHC4 Cafe Racer Fan]

Holy cow! Nice score! I'll give you $500 for it right now if you want to sell...


Wiring diagrams can be found here:

http://www.sohc4.net/cb750k-manuals/

Yeah.  That was a SMOKIN' deal. 

[Jerry Rxman Griffin aka MuthaF'er]

Wonder why they rigged the throttle cable like that? Stupidity? Pretty obvious where it goes. If you have a new petcock get rid of that external filter. It's probably toast anyway if not plugged.

[What2007]

Holy cow! Nice score! I'll give you $500 for it right now if you want to sell...


Wiring diagrams can be found here:

http://www.sohc4.net/cb750k-manuals/

Haha. I won't be ready to sell until I get her running and on the street. Got the dual piston calipers on order and a few other parts.

So are these fitted with a push/pull throttle from the factory?

I'm having issues with the throttle sticking after I go more than half throttle, looks like there may be a burr or something in there that I'll have to take a file to.

Also with the choke, any clue why it would be moving the arm but wouldn't be moving the butterflies?


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[madmtnmotors]

Also with the choke, any clue why it would be moving the arm but wouldn't be moving the butterflies?

You had the carbs off, did moving the choke linkage by hand actuate the choke plates? The choke linkage has a lot of travel. There's an adjustment in the cable itself that can be used to lengthen the choke cable sleeve, thereby adjusting any slack out of the linkage.

[madmtnmotors]

I'll give you $500 for it right now if you want to sell...

Haha. I won't be ready to sell until I get her running and on the street.

But for $500, your profit margin will be a lot slimmer after you spend all that money on parts!     

[What2007]

Also with the choke, any clue why it would be moving the arm but wouldn't be moving the butterflies?

You had the carbs off, did moving the choke linkage by hand actuate the choke plates? The choke linkage has a lot of travel. There's an adjustment in the cable itself that can be used to lengthen the choke cable sleeve, thereby adjusting any slack out of the linkage.

When I moved the arm that the choke cable attaches to, the plates did not move, but when I moved the little arm underneath that arm, they moved. I basically need to see how this is supposed to be set up on someone else's bike. Maybe if someone who is working on their bike could shoot a quick video or something that would be awesome.


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[What2007]

I found a video on YouTube of someone having the same issue

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[madmtnmotors]

I think the choke linkage is connected to the choke plates shaft(s) by a coiled spring. Check the choke plates for freedom of movement. If the choke plates or choke plate pivot shaft is gummed up and sticking then this coiled spring link may not be able to overcome the resistance (or the little coiled spring is missing or incorrectly installed).

[KRONUS0100]

awesome.  save another F model

[Statenheimer]

As others have said, fantastic deal you got there.

To answer your question, yes, it would have been fitted with push-pull cables from the factory.  Looks like the second cable is longer, and doesn't have the other on it.  Maybe they couldnt get it to fit in the stock location?

I would suggest new cables (many will suggest Motion Pro) to take a variable out of the equation and then determine if you are still having your throttle sticking issue.

Good luck.

[Stev-o]

I would suggest new cables (many will suggest Motion Pro) to take a variable out of the equation and then determine if you are still having your throttle sticking issue.

+1 new cables but not Motion Pro.  Spend a little more and get the proper Honda cable.  I recently bought some from DSS....

http://www.davidsilverspares.com/parts/

[dlhoulton]

Great score!! It's a diamond in the rough. As for your "oddball float". It's the correct float, but installed/mounted upside down.

[FuZZie]

Great score!! It's a diamond in the rough. As for your "oddball float". It's the correct float, but installed/mounted upside down.

Damn nice catch! but due to the float shape could it be the other 3 that are wrong?

[What2007]

Great score!! It's a diamond in the rough. As for your "oddball float". It's the correct float, but installed/mounted upside down.

Damn nice catch! but due to the float shape could it be the other 3 that are wrong?

According to the cmnsl parts fiche, the three are correct. Just the one was flipped. That is corrected now.


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[madmtnmotors]

Great score!! It's a diamond in the rough. As for your "oddball float". It's the correct float, but installed/mounted upside down.

Damn nice catch! but due to the float shape could it be the other 3 that are wrong?

According to the cmnsl parts fiche, the three are correct. Just the one was flipped. That is corrected now.


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What2007 is correct. When installed on the bike the flat side of the float faces down. When the carbs are removed from the bike and turned upside down the flat side faces up like the three in the photo of the OP. I'm guessing this is to give you a flat side when measuring float height.

[What2007]

I think the choke linkage is connected to the choke plates shaft(s) by a coiled spring. Check the choke plates for freedom of movement. If the choke plates or choke plate pivot shaft is gummed up and sticking then this coiled spring link may not be able to overcome the resistance (or the little coiled spring is missing or incorrectly installed).

I check that. Try blasting the area with some carb cleaner or something. The choke plates move when I move the little arm by hand, so they're not stuck. Maybe that little spring in there just isn't enough to move them with some help.


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[What2007]

I would suggest new cables (many will suggest Motion Pro) to take a variable out of the equation and then determine if you are still having your throttle sticking issue.

+1 new cables but not Motion Pro.  Spend a little more and get the proper Honda cable.  I recently bought some from DSS....

http://www.davidsilverspares.com/parts/

I will also check this out. I need to get in to the throttle to make sure the right one is on there and hasn't been replaced entirely.


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[AintNoEasyWay]

Definitely new cables. Glad someone else caught the float being upside down. I was hoping someone would say something before you put them back on the bike.

[What2007]

Well I went to put the new parts on today only to discover that the key had been left on and the battery died. Now I cannot get any power. I have the battery charger hooked up to my cables but get nothing when I turn the key. None of the three fuses are blown. Any ideas?


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[Stev-o]

Check the fuses with an ohmmeter to confirm they are good  clean the terminals with emery cloth.
A visual check of fuses may mislead you.

[What2007]

Check the fuses with an ohmmeter to confirm they are good  clean the terminals with emery cloth.
A visual check of fuses may mislead you.

Stev-o nailed it. I kinda feel like a dummy for that one.

The PO replaced the fuse with this long 15a, which is what I had to do since that's all I had available.


What fuses does this bike take? I just want to replace them all.


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[What2007]

As far as the choke issue goes, this little coil spring doesn't seem like it has enough ass behind it to operate the butterflies.
 



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