Carb Rebuild kit advice requested


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Hi All,
just joined and said hi in the lounge, but im looking for some advice on Carb Rebuild kits.

Appologies for my documentation skills, Bike runs nice but when i drop down a gear or open the throttle so that there is a high fuel demand it coughs and splutters, as such i thought i would have a look in the float bowls and they were grotty and showed signs of stangnent E10 fuel.

No problem I thought as i would take the carbs off and give them a quick clean up and they will be fine, but whist removing what i think it s the fuel air mix screw marked below as "1" a small washer fell out whilst spraying some carb cleaner around. I got my son to check them over as his eyes are much younger than mine and he spotted a small O ring seal that was under the washer, and spotted that it was split so we fished it out for a look, and it was.

The job then changed from a "quick clean" to a "we may as well completely restore them" job, so the question is what carb rebuild kit do you recoments either from the UK (preferably) or the US? I have read a lot that Randakks is the best, but i have also read that they sold out to another company, I have looked at Dave Silver spares, and NRP Carbs, but not sure which set to go for, any experience based recomendations?

The bank will get split and ultrasonically cleaned so i woudl rather do the job once and do it right so i can concentrate on just enjoying it.


I have the exact same bike and year as yours. I have used cheap alternatives and I have used Randakks kits (both for the CB and CBX) , lets just say that if you want to do this once, get the Randakks kit. Make sure to fish around for more washers and o-rings, I found multiple stacked on my CBX carbs. Also make sure to order the kit that have the air cut valves, you will have to change them too. I also recommend the Macgregor or Mike Nixon carb rebuilding guides!
Yes buy good kits. I think Randakk's is out of stock at the moment. As Brett mentioned there is All Balls and also Vintage CB750. Separate them all so you can replace the o-rings on the cross tubes. Leave no stone left unturned because it will come back to bite you in the end. I have read so many guys threads on here where they have taken the carbs off 3 or 4 times before they finally got it done. It only takes once if you do it right the first time. When you think you have them clean enough, do it again.
SO much truth to that, Loose Chain! I'm one of them. Pulled my carbs to clean them when I first got the bike and didn't replace the fuel rail orings. Next thing you know, dripping fuel when the petcock is on. Clean all the jets (there is one under the rubber plug), all air passages, fuel rail orings, bowl gaskets, ACVs, choke components if needed, too.
Have the MacGregor manual and have watched the YT video and to be honest its a class piece of work.

Invested in a ultrasonic cleaner (partially for the carbs, partially because he has access to an anodized at work), the carbs will be totally stripped and broken apart, I'm in no rush, took me 2 years to find the bike and I have ridden it 50 miles so know it will be worth it

Thanks all for the advice, shame randakks is out of stock, will email them tomorrow
I've bought stuff from vintagecb750, give them a shot, too.

I also should have mentioned in my previous reply: Polish the fuel inlet for each float bowl, too. Do not use any tool that scrapes! Use a qtip with brass Polish (that's what I do), then clean the passage out. If you nick the brass inlet, fuel will travel into that nick and past the float valve. You'll never get it to seal again.
Does anyone have any carb pre-cleaning recomendations that would get most of the varnish off prior to ultrasonic cleaning?
In the bowl and the jets, a brass brush to get crap out. I pluck a single wire brush strand and use it inside the jets. Spray carb cleaner through the fuel passageways and jets, then compressed air (50 psi to start) through all fuel passageways, jets, and air passageways. If you got that far and everything is clear, the ultrasonic cleaner will help with a fine cleaning.
If your question is more about the exterior of the carbs, you can use a Degrease (that is safe for aluminum) or soap and elbow grease.

Any idea why 3 of the carbs have this brass insert standing proud, and on carb 3 the insert is flush?

I am concerned that the 3rd carb was a replacement and might be adding to the poor running

Randakks full rebuild kit ordered, carbs have been cleaned now
That piece might be missing. It is held in place by the emulsion tube/jet holder. If it was missing before you took them apart it would have run poorly. It would flood so bad in that cylinder it wouldn't even fire. What did the plug in that cylinder look like?
Thanks @Loose Chain you gave me the clue i needed and the panic is over. The clue was "held in place by the emulsion tube", which had been removed for some serious cleaning, and as i have ultrasonically cleaned them, and could see a bit of brass in the hole i went and put a drift down the hole and gave it a couple of light taps, it popped up.

Clearly during the cleaning process it had dropped down a little, thanks to all for the advice recieved so far, this is my first time stripping carbs and the forum help along side of the cleaning vids and instructions have given me the confidence to do the job, heard from Randankks today that the carb kit had shipped so they should hopefully be here ina week and i can start putting it all back together.
I see you also removed the throttle plates, some of the guides I have seen advise against it since there are small felt washers that needs to be replaced there if you take them apart. But I also think Mike Nixon have an article about the washers not being that important. Anyway your Randakks kit wont include them.
I see you also removed the throttle plates, some of the guides I have seen advise against it since there are small felt washers that needs to be replaced there if you take them apart. But I also think Mike Nixon have an article about the washers not being that important. Anyway your Randakks kit wont include them.
Thanks, I did find the felt washers were found intact, removed ans safely stored just in case
Whilst awaiting my new seals from Randakk's i thought i would have a look at the carbs, clearly at some point when the bike was recomissioned the carb tops must have been in quite a state and someone took a heavy grade sandpaper to the tops to clean them up.

They did some damage though, so i decided to start cleaning them up staring with 600 weight wet and dry, that has been followed by 1000 weight, then i will use some very fine alloy polishing sandpaper that my son can get (unusable scraps from work) that hopefully will reduce the hazing to a point where some solvol autosol can be used to do the final polishing with a dremel and some mops.

Hopefully i can get them all polished and looking better before the rebuild kits turn up, will keep people informed, but if anyone has any advice feel free to pass it on where i will happily accept it.


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