New Member - 1978 CB400a Hondamatic "build" questions

[hubbard_86]

Hello all! Just picked up a 78 CB400a (yes, that's an automatic...eek!). But, I got it for free, so I'm not complaining. I changed the plugs and I could get it to idle. As soon as I gave it gas it shuts down. Oh, I found the manual via the Do The Ton forums, so much praise to all!

As for the carbs, it's pretty clear that the jets are plugged up. So, a few quick questions:

1. What's the best resource to get a carb rebuild kit? It has 2 Keihin VB24a carbs but I can't locate any rebuild kits via Google searches.
2. Do I really need a rebuild kit or can I soak the carbs and then reassemble with the original gaskets, etc...?
3. How about the liquid gasket stuff? Any brand recommendations or if I should even attempt to go that route?

That's about it for now. Took the carbs out yesterday and I'm itching to get the bike running for a few weeks before the cold RI winter hits!!!

Billy

 

[my-79-750-k]

Clean the carbs, but don't use the old gaskets. They're out there, you just have to look. As much as I hate to say it, eBay might be your best bet. Gasket kits shouldn't be too much for carbs. As for the jets, clean, clean, clean.. and then clean some more. Go to your local hardware store and get a "torch tip tool". It looks like a little hand set of picks, but in all kinds of sizes, runs about 5$. Use those to clear out any gunk that won't come out from cleaning, and then, clean them some more. Use new gaskets, set your float height and reset your idle/air/fuel screws to factory settings. Replace your plugs and your fuel lines, and maybe add a fuel filter (ethanol approved, ehh). If it won't run after all that, then there's more issues, but that'll eliminate your fuel delivery system for not a lot and you can move on to something else.

You may end up having to buy a scrap set of carbs on eBay. Just keep your eyes open. I ended up getting an entire bank of carbs for my 750 on eBay for 50$. 3 floats, new bowl screws and a full set of stock jets, plus extra carb body parts. The deals are there, just gotta be online when they appear.

 

[my-79-750-k]

Oh, and ixnay on the liquid gasket. It's great for some things, carbs are not one of them.

 

[hubbard_86]

Thanks Jewbacca. Great advice! So, a question about searching the web for the carb kits... I have the Clymer manual and it lists them as "Keihin model VB24a" but that doesn't really get me any hits. Should I just look for Keihin 24mm carb kits? Are they universal or does the VB24a specify a certain style, etc...?

Thanks again!

 

[benwstewart]

Just wondering how this went. I had the similar problem on my 78 cb400a and it ended up being the torque converter. It idled fine but as soon as you put in 1st or gave it gas it would shut off. Hope it worked out for you.

 

[brandonBZ]

hey I have this same model of bike and I am getting started on getting up and running. But as for the Carb rebuild kits the official ones are few and far between on ebay and go for 38 bucks all the way to 70.

Here is a universal one that should fit yours. I just bought 2

http://www.jcwhitney.com/bikerxxs-choice-universal-keihin-carburetor-parts/p2028730.jcwx?skuId=1014449&filterid=c51113d57979u0j1

let us know whats going on with your project.
I'm gonna try to start up a thread on here