Topic: carb cleaning

[bultaco59]

Hello out there in cb land,

I have a few questions about cleaning on a 78 cb 750k, the bike i bought didnt
come with carbs, so i bought a set on ebay now they must be rebuilt, what is the best way to approach this.? i have never rebuilt a set of four carb the most
i have done is a twin. should they be completely disassemabled or can i clean them
without seperating them. im guessing no. but it cant hurt to ask. any help would be great.

thanks
bob in burbank

[BobbyR]

The quick answer is you do not have to separate the carbs unless something else is wrong. I also have a 78K and we have an accel pump, that always gums up badly. You can do a search and get a lot more detail. The one piece of advice is to take your time and make certain you open all passages. If you don't you will do it again and again. Simple Green will eat up the gum in most parts. 1 hr at 100% and no metal will be discolored. The slow jets do pull out and have to be really clean.

Do a site search and you will find a lot of stuff and more detail.

[flybox1]

hey bob....whats the model # of your carbs?
look on the outboard side of carb 1 or 4 at the bowl mating surface.  should be stamped there.

[Cabilao]

I soaked mine in 50/50 solution of simple green and water for 3 hours. Little work with the tooth brush and clean. Leave them on the rack but removed the bowls,floats and jets. Check the threads here in the forum,a lot about carb cleaning.

[bultaco59]

Thanks guys for all the info. Flybox asked me what model carbs, the carbs are
Keinin and the # is PD 44A0C7 THERE ON A 78 CB750 K Im going to soak them tonight. one quick question does the needle valve need  to be replaced, can you pull slides without serperating carbs.

thanks

Bob in burbank

[BobbyR]

Thanks guys for all the info. Flybox asked me what model carbs, the carbs are
Keinin and the # is PD 44A0C7 THERE ON A 78 CB750 K Im going to soak them tonight. one quick question does the needle valve need  to be replaced, can you pull slides without serperating carbs.

thanks

Bob in burbank

Yes the slides can be removed without seperating take your time and you will figure it out.  You can slide them up through the top. Inspect the needles.  Polish the slides they are chrome and it will make them work smoother.

[flybox1]

no need to remove the needles from the slides.  just clean.  as bobbyR stated.  polish the slides. 
Looks like you have an accelerator pump on these....and (i'm assuming as i cant see it) a fast idle cam... somewhat tedious to dial in, but when operational, it will make starting and idle much easier.  top of carb bowl #2 there should be a small o-ring.  dont lose it.   in picture #1 above you it shows 3 transverse black fuel lines just above the carb bowls.  there should be hard brass tubing inside.

[Toxic]

Don't assume the jets are the same in each carb.

Read lots about float bowl height and how to set it.

If you take the time to set up something like this:


It will save you time and effort if you don't get the float height bang on the first time.
I thought I had it right the first time but it took 3 tries to get it perfect.