Author Topic: My $75 Supersport Resurection (Read 9020 times)

What2007 · « **on:** March 30, 2014, 03:13:38 PM »

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 · « **Reply #1 on:** March 30, 2014, 03:20:36 PM »

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 · « **Reply #2 on:** March 30, 2014, 05:57:00 PM »

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 · « **Reply #3 on:** March 30, 2014, 06:18:13 PM »

Quote from: madmtnmotors on March 30, 2014, 05:57:00 PM

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 · « **Reply #4 on:** March 30, 2014, 06:23:25 PM »

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 · « **Reply #5 on:** March 30, 2014, 07:21:43 PM »

Quote from: madmtnmotors on March 30, 2014, 05:57:00 PM

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 · « **Reply #6 on:** March 31, 2014, 04:32:39 AM »

Quote from: What2007 on March 30, 2014, 07:21:43 PM

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 · « **Reply #7 on:** March 31, 2014, 04:36:17 AM »

Quote from: What2007 on March 30, 2014, 07:21:43 PM

Quote from: madmtnmotors on March 30, 2014, 05:57:00 PM
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 · « **Reply #8 on:** March 31, 2014, 04:41:56 AM »

Quote from: madmtnmotors on March 31, 2014, 04:32:39 AM

Quote from: What2007 on March 30, 2014, 07:21:43 PM

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 · « **Reply #9 on:** March 31, 2014, 07:11:45 AM »

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

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madmtnmotors · « **Reply #10 on:** March 31, 2014, 07:44:37 AM »

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 · « **Reply #11 on:** March 31, 2014, 11:18:58 AM »

awesome. save another F model

Statenheimer · « **Reply #12 on:** March 31, 2014, 12:03:55 PM »

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 · « **Reply #13 on:** April 01, 2014, 05:56:27 AM »

Quote from: Statenheimer on March 31, 2014, 12:03:55 PM

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 · « **Reply #14 on:** April 01, 2014, 08:23:29 AM »

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 · « **Reply #15 on:** April 01, 2014, 10:09:31 AM »

Quote from: dlhoulton on April 01, 2014, 08:23:29 AM

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 · « **Reply #16 on:** April 01, 2014, 10:21:49 AM »

Quote from: FuZZie on April 01, 2014, 10:09:31 AM

Quote from: dlhoulton on April 01, 2014, 08:23:29 AM
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 · « **Reply #17 on:** April 01, 2014, 11:00:22 AM »

Quote from: What2007 on April 01, 2014, 10:21:49 AM

Quote from: FuZZie on April 01, 2014, 10:09:31 AM
Quote from: dlhoulton on April 01, 2014, 08:23:29 AM
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 · « **Reply #18 on:** April 02, 2014, 07:12:56 AM »

Quote from: madmtnmotors on March 31, 2014, 07:44:37 AM

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 · « **Reply #19 on:** April 02, 2014, 07:14:01 AM »

Quote from: Stev-o on April 01, 2014, 05:56:27 AM

Quote from: Statenheimer on March 31, 2014, 12:03:55 PM

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 · « **Reply #20 on:** April 02, 2014, 12:45:56 PM »

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 · « **Reply #21 on:** April 02, 2014, 05:02:33 PM »

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 · « **Reply #22 on:** April 02, 2014, 05:34:41 PM »

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 · « **Reply #23 on:** April 02, 2014, 06:08:26 PM »

Quote from: Stev-o on April 02, 2014, 05:34:41 PM

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 · « **Reply #24 on:** April 02, 2014, 06:18:23 PM »

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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madmtnmotors · « **Reply #25 on:** April 02, 2014, 06:41:00 PM »

It shouldn't need much ass. The chokes should rotate smoothly. Lube the shafts and check the motion of the choke plates for any resistance. Check that the spring appears to engage both components. Look for anything that might be bent or loose.

What2007 · « **Reply #26 on:** April 02, 2014, 07:02:28 PM »

I'll bring the whole thing in to work tomorrow and see what I can do to loosen everything up.

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What2007 · « **Reply #27 on:** April 03, 2014, 06:17:45 PM »

Choke is still acting up, but it's a little better. Ordered new cables and such.

Trying to get this damn thing started is driving me nuts. I can get it run off of ether, but no luck just on gas. I'll go through them again and if I can't get it this weekend I'll just have them rebuilt.

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What2007 · « **Reply #28 on:** April 09, 2014, 07:11:52 PM »

Got her to fire up tonight. It'll only stay running if I fiddle with the choke though. I have the needle at 2 turns so I'm going to put it at the 1.5 I keep reading about and try it again. Also going to need new bowl drain plugs as all 4 of them leak now since I cleaned everything.

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What2007 · « **Reply #29 on:** April 10, 2014, 05:19:54 PM »

Here's a video. Little smokey. Still need to do some carb adjustments.

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What2007 · « **Reply #30 on:** April 12, 2014, 02:59:45 PM »

Put on some euro bars. Kind of wish I had a longer clutch cable. Broke my choke assembly in the process unfortunately.

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SOHC4 Cafe Racer Fan · « **Reply #31 on:** April 13, 2014, 10:51:12 AM »

Nice bars.

What2007 · « **Reply #32 on:** April 18, 2014, 07:42:51 PM »

Could somebody please tell me how to route these breather lines?

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colvinry · « **Reply #33 on:** June 14, 2014, 11:08:45 AM »

What2007 could you take some more pics if the carb mechanism, I cannot figure mine out. I took my carbs apart for cleaning and rebuild and am having trouble getting the carb cams to link up properly. An pics or advise will help. Here is a pic of where I am at. It is close but I feel like I am doing something goofy.

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Author Topic: My $75 Supersport Resurection (Read 9020 times)