Topic: 750K4 - Removing carbs for the first time. Any words of advice for a novice?

[djwillard18]

A significant gas leak appeared the last time I attempted to ride to work. After a little poking around I believe the leak is at the T-inlet on the left pair. After doing some forum-research, I think it is probably the O-rings on both sides of this piece.


I've never removed the rack of carbs before and want to reduce my odds of messing anything up.


(1)  How should I approach this?
(2)  Tips/tricks and things I should never do.
(3)  Other than replacing these O-rings, what should I think about doing while they're off?


Thanks in advance for your time and sharing your knowledge!

[MauiK3]

Remove the tank and air box
Drain the bowls
Try to mark the rotation of the “insulators”, the rubber connectors between the carbs and head.
Note the routing of all the lines, photos help. Note how the fuel lines go from the peacock to each pair of carbs, don’t ask why I say this.
If your band clamps are in bad shape plan on replacing them, this goes for the insulators too, if they are stiff it will be hard to get them to seal and drive you nuts.
If the fuel lines are stiff  ( 5.5mm, Black Honda is the best) and old, plan on getting new ones.
Disconnect the cables. Note routing.
Rock the carbs off the rubber insulators
After you have them on the bench, it’s all you.
Might be a good time to look inside each carb.
If you have an ultrasonic cleaner and some 50-50 simple green and water a good cleaning will be great.
I’m sure I missed some things here.

[djwillard18]

Thank you, MauiK3.  Just need to make some time and space to work on this. Have to order some supplies, too.

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[ekpent]

 Have a heat gun handy and warm up the rubber manifolds until the are hot and supple and soft as a babies behind  A little grease or such and heat will help on the install also. Looks for some 8mm x 2mm rings for the fuel tees.You need 8 pcs to do both. New fuel line is a good idea while they are off also. Do not fiddle with the synch adjuster nuts when breaking down the rack,no need to. Its all a pretty easy project.
 +1 on replacing those clamps if they have stretched a little and the old rubber has shrunk.

[flybox1]

Just a general cleaning and spray/through of all jets and passages.
The best thing for your carbs is the OEM Keihin brass parts (if you are retaining stock configuration).  Jets, needles, and emulsion tubes.
No need to throw them out if they are dirty or slightly scuffed from your bikes PO....they're still good.
Check that they are clean and clear thru, and put them back in.
The stuff they sell in cheap kits just isnt as good as it needs to be...

[Johnie]

You said you are a novice...those sync adjusters ekpent is talking about are the nuts that are over the arm on top of each carb. If you turn those you have to sync the carbs all over again. Once you take the philips screws out from the back of the rack the carb arms will slide right off. Good luck and hit us up with more questions...it's really quite simple and you will find that out after your first time. Make sure you change those o-rings in both fuel T's. I get mine from NAPA part number 727-2605.

[djwillard18]

Thanks, Johnie, flybox1 and ekpent.


Yes, I am a novice, so all tips are appreciated!  The NAPA part number is a great help.


Probably tackle the tear-down Sunday after I get a heat gun.

[Progas]

Replace the intake manifolds while you have the carbs off, you'll be way ahead of the game.

[evanphi]

Yeah if those rubbers are stiff buy new ones. Go with original Honda (still available!) The aftermarket ones fall apart quickly.

[djwillard18]

Do you think this deal is too good to be true?  Four Genuine Honda manifolds (insulators), with 8 clamps for $65.


https://www.ebay.com/itm/Genuine-Honda-CB750-Intake-Insulators-Carb-Holder-w-Clamps-K-71-76-F-75-76/192606997978?hash=item2cd8458dda:g:WAgAAOSw44BYE7Yz:rk:12:pf:0

[Johnie]

Heat gun = a hair dryer.

[madmtnmotors]

Do you think this deal is too good to be true?  Four Genuine Honda manifolds (insulators), with 8 clamps for $65.


https://www.ebay.com/itm/Genuine-Honda-CB750-Intake-Insulators-Carb-Holder-w-Clamps-K-71-76-F-75-76/192606997978?hash=item2cd8458dda:g:WAgAAOSw44BYE7Yz:rk:12:pf:0

For the price I would probably try them. I would plan to inspect them at least once a year for signs of distress (i.e. cracking). I may order a set just to have them on hand. Cheap OEM style clamps will set you back close to $20 for eight, so you get the boots for about $50.

If you look at the seller profile it is the ebay outlet for CB750Supply.com. They get $75 for the boot/clamp combo on their website:
https://www.cb750supply.com/products/6/fuel-system/54/carb-holders

[ekpent]

 I've done many ,many cb750's and have never replaced a single rubber manifold ever. Your call but there have been complaints with some of the aftermarket ones. Heat makes the old ones workable but I always ditch the old clamps into a keeper box and upgrade with better.

[PeWe]

PITA to mount the carbs on the carb boots without warming them first, even when they are new. I use a heat gun, not for hair since it will burn Keep distance and move constantly. Same gun used for bearing assembly and fork seals removal/assembly.

[djwillard18]

Do you think this deal is too good to be true?  Four Genuine Honda manifolds (insulators), with 8 clamps for $65.

https://www.ebay.com/itm/Genuine-Honda-CB750-Intake-Insulators-Carb-Holder-w-Clamps-K-71-76-F-75-76/192606997978?hash=item2cd8458dda:g:WAgAAOSw44BYE7Yz:rk:12:pf:0

For the price I would probably try them. I would plan to inspect them at least once a year for signs of distress (i.e. cracking). I may order a set just to have them on hand. Cheap OEM style clamps will set you back close to $20 for eight, so you get the boots for about $50.

If you look at the seller profile it is the ebay outlet for CB750Supply.com. They get $75 for the boot/clamp combo on their website:
https://www.cb750supply.com/products/6/fuel-system/54/carb-holders

Thanks for your advice.

[flybox1]

PITA to mount the carbs on the carb boots without warming them first, even when they are new.

Sure!
But, if you cant sneak off with your significant-others hairdryer, a little gen-purpose grease on the insides of the boots goes a long way...

[madmtnmotors]

Do you think this deal is too good to be true?  Four Genuine Honda manifolds (insulators), with 8 clamps for $65.

https://www.ebay.com/itm/Genuine-Honda-CB750-Intake-Insulators-Carb-Holder-w-Clamps-K-71-76-F-75-76/192606997978?hash=item2cd8458dda:g:WAgAAOSw44BYE7Yz:rk:12:pf:0

If you look at the seller profile it is the ebay outlet for CB750Supply.com. They get $75 for the boot/clamp combo on their website:
https://www.cb750supply.com/products/6/fuel-system/54/carb-holders

Thanks for your advice.

Be sure to keep the original boots if you try the aftermarket ones. If the aftermarket ones fail miserably you can always reuse the original ones, even if you have to warm them up as suggested to make them a little more pliable. 
For the price I would probably try them. I would plan to inspect them at least once a year for signs of distress (i.e. cracking). I may order a set just to have them on hand. Cheap OEM style clamps will set you back close to $20 for eight, so you get the boots for about $50.

[djwillard18]

SUCCESS!!  Removed the carbs yesterday and fixed the T-joint. Today reinstalled everything. NO leak and it started right up!

Thank you all!

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[Johnie]

Yah, it is scary the first time. It gets faster each time you do it.

[madmtnmotors]

I love it when a plan comes together! 

[ekpent]

 Did you replace the rubber manifolds or keep your old ones ?

[djwillard18]

I was able to reuse the existing ones; they were like new.  Very pliable and came off and on without much trouble.

I did have a self-inflicted challenge when I slid the "choke-rod" out of the carburetor instead of just disconnecting the linkage. That took about 10 minutes for me to get the little arm inside lined up and reconnected with the baffle.

I am pleased with how everything fit together so precisely. Another project this weekend from the Honey-do list didn't give as much time as I hoped, but,even so, it is ready to ride.

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