1992 CB750, first time tackling carbs

[AlwaysAdar]

Picked up a 1992 CB750 about two weeks ago.  1-owner bike that had been traded to a tradesman in exchange for work had kept it in a shed for a couple of months.  Carbs needing work were discussed at the time of purchase.

I'm familiar with doing some basic vehicle maintenance.  Came into this figuring I'd tackle some repair/task on every other weekend.
Something to keep me busy, learning new things, and an excuse to build up my tools.
I have digital copies of the common service, model-specific, and Cyclepedia (got it for $2.50) manuals.
Regardless of my efforts, I will have a mechanic look over before I do any riding (which will make the Miss a bit happier).

The bike starts with some choke but dies when throttled unless warmed up.
Ran some sea foam through it. Kind of helped, but still dies.
The bike recently stopped running, but it seemed to be a battery problem. The battery is from 2018; I put a tender on it for now but plan on switching it out when it's closer to rideability.

I've never worked on carbs.
A problem I encountered was that there seemed to be so much other work that would be optimal to do while cleaning the carbs since the tank would be off. Seemed like a good time to change the throttle cable, rubber manifolds, fuel lines, and spark plugs, along with rebuilding the petcock and synching the carbs since I'm already taking off the gas tank.

Also, got stumped about what carb rebuild kit to buy. I'm kind of assuming the kits that seem affordable though busy with all included parts, are probably of a lower quality.
I definitely need/want to tackle the carbs. I think I just need to get them off and cleaned first; then I'll have a better idea of what I need.  I can always take the gas tank off again.

Suppose the carbs sit off the bike for a week or two while I figure things out. Not a big deal.
I've so far done an oil change.  I'm cleaning the battery terminals to add pigtails and replacing the air filter.

I was going to get an ultrasonic cleaner, some carb cleaner,
Any advice on figuring out what to tackle, in which order, and what to buy?

[Bob H]

I've never worked on carbs.

Also, got stumped about what carb rebuild kit to buy. I'm kind of assuming the kits that seem affordable though busy with all included parts, are probably of a lower quality.
I definitely need/want to tackle the carbs.

If you start with page 5 on "what did you do to your NH today" you will encounter my thoughts on the carbs.
https://nighthawkforums.com/index.php?topic=39.60

You will also see a lot of input on special tools to reach the pilot adjusting screws - none of them will fit in the tight space. So don't get too hung up on that.

But for the basic question you are asking, I got an ultrasonic similar to the one Harbor Freight sells (but I got it on Amazon). and it is OK for doing one carb body at a time.

There are lots of videos on youtube re: carbs, and I likely watched all of them. It is a great orientation.
I spent a fortune on OEM gaskets and diaphrams from Partzilla. If money is tight you can try your luck with the super cheap ones on Ebay from China. I ordered them too, then changed my mind before they even arrived when I realized how much of my time was going to be spent, and didn't want to cheap out on parts.

The best $40 I spent was to pay for the educational video series from motorcycle md that I link to on pg 5 of that other thread. Although I did the carbs about 10 years earlier and know my way around tools, I found the videos very helpful. And it is for your exact model.

He also has various free videos, and some of them are part of that course (like how to remove the carbs) and you can see those on youtube to get a feel for if his lessons are a good fit for you.

As for jets, your carbs are made by Keihin, and if you order the kit for your bike from carbjetkits.com the product you will receive is also made by Keihin. The kit I got that finally arrived from China "looked OK" but the jets had no mfg marking on them (clones).

As I mentioned in the other thread, I ended up getting gaskets from partzilla to make sure the fuel rail O-rings were correct (not included in the Ebay set I don't think) as they had been problematic and leaked if the bike sat for a month or so. the new O-rings solved that.

[mollusc]

If you're tackling the carbs, it's best to tear them down all the way and separate them from the mounting rails so you can replace the o-rings on the pipes that connect each one.  To do this you will need a proper JIS bit.
THERE ARE NO PHILIPS SCREWS ANYWHERE ON YOUR BIKE.
If you try to use a Philips head driver on the mounting screws, you WILL strip them.  I tend to replace them with stainless bolts when I'm reassembling, just to make things a bit easier next time.

Replacing the fuel line and vacuum line is a sensible idea.  Not difficult, not expensive.  Don't touch the petcock unless it's leaking or malfunctioning.

The most important thing to worry about when you're cleaning the carbs is to make sure you know where ALL the little parts are that you need to remove.  There are jets and plugs and springs and tiny washers and o-rings.  Each carb is essentially the same inside so once you've done one, you will recognise the others.  Keep the parts for each carb together with the carb body -- don't mix them together.  If you get 4 kits, you will have a few pieces left over because each kit comes with o-rings for the air and fuel pipes on both sides, and the outer carbs only have pipes on one side.

You will need to sync the carbs after you're done cleaning them.  Doing a bench sync is mandatory, and pretty simple.  You don't need to worry about how to do it until you get there.