Topic: Dismantling the Honda 400 four carbs

[nargent]

Hi. I'm quite new to all this. As a youngster I rode a 400 four, 550 four and 750 KZ (not at the same time). Now 30 years later I have picked up a 76 Honda 400 four in reasonable shape, but stuck in a shed for 15+ years...

I have had a look in one of the carbs and unsurprisingly it is gummed right up. I have been working on cleaning it up (with a lot of help from these fora) but would like to separate the four carbs and give a really good clean of the outsides as well as the insides. Problem is, I can't figure out how to separate them! The Haynes manual doesn't really help much.

Is there some magic nut and bolt that I haven't seen that will allow me to take these things apart?

Many thanks in advance

[flybox1]

Its been a.few years since I had 350f carbs in my hand, but IIRC, there should be a plate they are mounted too, just like the CB750 PD carbs.

[Deltarider]

but would like to separate the four carbs and give a really good clean of the outsides as well as the insides

. I don't recommend separating the carbs. The insides can be perfectly cleaned unseparated. Just remove the bowls. I can imagine after 15 years in the shed the insides are horrible, for the outsides it doesn't make much difference. And then... it usually takes a few rides and they're all dirty again. But if you must, you must.

[Bodi]

It isn't really difficult. Get a 4-pack of food storage tubs (ziplok?) at the grocery store and label them 1 to 4. Keep each carb's bits in its tub. There will be a few parts not specific to any carb so you will need a smaller "common parts" container.
Take a LOT of pictures of the linkages and choke connectors etc before starting. They look like "easy as pie, only one way those will go together" but they look a lot different and not at all obvious when trying to reassemble.
Only the throttle linkages need to be disconnected to remove the bodies as I recall. The link between the throttle rod arm and the carb arm works with a steel ball snapped in between two black plastic or graphite parts in the link bar. Unscrew the outer carb from the bracket and gently pull the ball out of the link. Be super careful with the rubber seal and the thin metal "barbell" joining the links.
Watch out for the return spring pin, between 2 and 3. It is easy to lose. If you take the choke lever off, watch out for a tiny (TINY!) spring and tinier steel ball for the click detenting.
I don't recommend dismantling the throttle mechanism and can't help with it - never tried. It seems to have pressed in pins somewhere. Unless you want to install a high ratio smaller pulley there's nothing to gain - provided you don't want a concours restoration replating I suppose. You can clean it to "very pretty!" condition with solvol, a toothbrush, and a few hours cursing.
You will want 4 OEM carb gasket kits. These have the cap and bowl gasket and pretty much all the O-rings you need.

[Csrgti]

I honestly don't believe you can do a thorough job of cleaning the carbs without removing them from the rack.
Search online for as many technical drawings and how to's you can find on the internet, make sure you have a wide selection of good quality  screw drivers, a hand held impact driver ( used by hand never actually hit it with a hammer on your carbs)  and small metric sockets. Do not disassemble them all at the same . If you do them one at a time you'll always have another carburetor as reference if you get lost. When I did mine I soda blasted them first then washed with soap and water , then disassembled them and soaked them for about an hour.
 There's all sorts of solutions people use to soak them, mine weren't horrible, so I just used straight gas.
Then went through every jet , hole, corner, etc, with small nozzle brushes,tooth picks, strands of wire etc.
Along with aerosol chem tool B12. I was taught that any discoloration inside is dirt and will potentially clog your carb once gas has sat in it and has a chance to loosen it up, so whatever carbs I'm working on get cleaned back to their factory finish.  Take your time and be thorough . When reinstalling the slides make sure the bores are spotless and slide freely , mine would bind up when they were tightened unless they were held in just the right way.
Personally I thought it was a great way to spend a day and wish I had more to do
 ( I need another project bike)

[nargent]

Thanks very much for the replies. I had meant to get back to this thread a while ago but couldn't find it! Here I am now.

I got the carbs apart and have done a thorough inside and out clean up. There was a lot of crap in them - 4-5 mm thick gunk and all the jets were totally bunged up. Put them back together with the carb rebuild kits from 4into1 and am fairly happy with the result so far. I messed up by breaking the little black doodad that joins carb 1 and 2 as I took them out, but I have machined a new piece out of brass that should fit nicely. Now I have to find some 5.8 x 1.9 mm o-rings...

I am planning to strip the bike down, get the black bits powder coated, generally make things pretty. Since the bike didn't run when I got it (many years sitting in a shed in Ontario) I am also planning to take the motor apart and fix anything that needs fixing. Its as much for me to learn about the engine and have fun than anything else. I have been browsing the various threads and am amazed at the depth and breadth of knowledge out there. Hoping to be able to get help as I go along as I am sure to need it!

Thanks in advance.