Topic: My 1976 CB400F Restoration Project Has Arrived

[denward17]

On my 550, I just relent and remove the battery/battery box, and air box.  The clamps on the airbox side are entirely removed as well, as not to damage the air horns.

Yes, lots of work, but much easier to get carbs out.

[Mark1976]

On my 550, I just relent and remove the battery/battery box, and air box.  The clamps on the airbox side are entirely removed as well, as not to damage the air horns.

Yes, lots of work, but much easier to get carbs out.

Been there done that, the 550 is a bit more involved, no fun.... The 400f really isn't that difficult, remove the air chamber and there's plenty of room.

[WingMan71]

Been there done that, the 550 is a bit more involved, no fun.... The 400f really isn't that difficult, remove the air chamber and there's plenty of room.

Right!  But, it's that "just remove the air box" part that isn't at all easy either.   

[Mark1976]

Been there done that, the 550 is a bit more involved, no fun.... The 400f really isn't that difficult, remove the air chamber and there's plenty of room.

Right!  But, it's that "just remove the air box" part that isn't at all easy either.   

Push the oval tube that connects the airchamber to the airbox back, the airchamber slides right out.

[WingMan71]

Push the oval tube that connects the airchamber to the airbox back, the airchamber slides right out.

Thought of that.  Neither item 5 or item 6 would budge even a tiny bit.  Any more effort exerted on those parts and they would have broken/cracked.

The only thing I could do was to force the air box off of item 5 toward the front of the bike.  Not easy but it worked.

Air box removal or reinstallation would be way easier if either item 5 or 6 could be pushed at least partially into the air filter housing, but I can't get either one to budge.

This bike sat in storage for over 20 years.  Things are stuck together tighter than a duck's butt.

[Mark1976]

   The big oval grommet the seals the tube to the airbox will push into the airbox, it'll be tough pushing it out the first time, once its out you'll notice that the tube has a lip that rides in a slot in the grommet. Pull it out of that and from that point forward just reinstall it in the grommet in the airbox, then push the tube thru from the airbox side (use a little lube on the inside and outside of the grommet, makes it that much easier the next time). It'll still reach the airchamber and the next time you need to pull the rack, you just pull the oval tube out and then the airchamber. No wrestling and or swearing required.

[WingMan71]

   The big oval grommet the seals the tube to the airbox will push into the airbox, it'll be tough pushing it out the first time, once its out you'll notice that the tube has a lip that rides in a slot in the grommet. Pull it out of that and from that point forward just reinstall it in the grommet in the airbox, then push the tube thru from the airbox side (use a little lube on the inside and outside of the grommet, makes it that much easier the next time). It'll still reach the airchamber and the next time you need to pull the rack, you just pull the oval tube out and then the airchamber. No wrestling and or swearing required.

So, don't seat the metal tube back into the lip in the big grommet?

It will still stay in place in the grommet just from friction fit?

Just hope I can push that big grommet into the air filter housing.  It's really hard and not very pliable anymore.  I'll say a prayer and then give it a shot.

[newday777]

Heat old rubber with a heat gun to make it pliable to get in place.

[Mark1976]

   The airchamber seal has a clamp on it, that keeps it in place.

[WingMan71]

   The airchamber seal has a clamp on it, that keeps it in place.

That clamp/band, item 13 in the microfiche, was actually missing from my bike.  Saw it in the microfiche, but it's gone from my bike.

So, at some time in it's 48 year history, the carbs have been off of this bike before.

It looks like the band actually holds the metal tube, item 5, onto item 6, the gasket.  I think the gasket is held in place in the air filter box with just a friction fit.

Since the band is not there, I may be able to just tap the metal tube through the gasket and into the air filter box with a rubber mallet.

[Mark1976]

   The band holds the air chamber grommet onto the tube, the airbox grommet is a pinch fit held in place by the tube. Once you have the carburetion figured out you can then reinstall as per the original method, it's just easier this way till you've figured out the carburetion issues.
   Get the band clamp, the fit of the tube to the air chamber grommet is not the snug, hence the band clamp.

[WingMan71]

   The band holds the air chamber grommet onto the tube, the airbox grommet is a pinch fit held in place by the tube. Once you have the carburetion figured out you can then reinstall as per the original method, it's just easier this way till you've figured out the carburetion issues.
   Get the band clamp, the fit of the tube to the air chamber grommet is not the snug, hence the band clamp.

That band clamp seems to be unavailable.

Since it's out of sight, think I'll just use a standard worm-gear style hose clamp, or a big wide cable-tie.  Should work fine.

[Mark1976]

   The band holds the air chamber grommet onto the tube, the airbox grommet is a pinch fit held in place by the tube. Once you have the carburetion figured out you can then reinstall as per the original method, it's just easier this way till you've figured out the carburetion issues.
   Get the band clamp, the fit of the tube to the air chamber grommet is not the snug, hence the band clamp.

That band clamp seems to be unavailable.

Since it's out of sight, think I'll just use a standard worm-gear style hose clamp, or a big wide cable-tie.  Should work fine.

[WingMan71]

Finally got the metal air duct pushed through the big seal on the air filter housing!  Yay!  I'll be able to reinstall the air box and the carbs now when I'm done with them.

I got it pushed through the big seal lip by lubing up the ID of the seal with rubber grease a bit, then used a scissor jack with wooden boards on both sides to push it through the seal.

[WingMan71]

So, I'm stuck!

Honda Factory Service Manual says to remove the adjuster holders from the link arm.

I'm about 1/8" of an inch short of enough room to get them off!  Factory manual picture actually shows the same space problem.  Hah!

Now what? Got to get all four of them off or I can't separate the carbs from the huge back bracket and each other.

See attached pictures.

[denward17]

You might have to separate the carbs before removing the arms, but just a guess, wait for others with more experience on these.

[Mark1976]

   So before you too much further, what are your objectives in regards to working on the carbs? I'm not saying you should disassemble the entire rack, but at this point what are you trying to accomplish. Just asking...

[WingMan71]

   So before you too much further, what are your objectives in regards to working on the carbs? I'm not saying you should disassemble the entire rack, but at this point what are you trying to accomplish. Just asking...

They look terrible, on the outside.  They have been sitting for over 20 years.  Haven't seen how bad the inside is plugged up yet, but I'm sure it's pretty bad.

I want to do a complete rebuild including vapor blasting every part of it so that they look like new when done.

Going for a "Condition 2 - Excellent" restoration.  Not trying for a "Condition 1 - Show Quality" bike.

[Mark1976]

   So before you too much further, what are your objectives in regards to working on the carbs? I'm not saying you should disassemble the entire rack, but at this point what are you trying to accomplish. Just asking...

They look terrible, on the outside.  They have been sitting for over 20 years.  Haven't seen how bad the inside is plugged up yet, but I'm sure it's pretty bad.

I want to do a complete rebuild including vapor blasting every part of it so that they look like new when done.

   Ok, try to take some picks as ya go if your not familiar with this rack, it'll help putting it back together, especially the adjusters. So many individuals on here have pulled them completely down and then have a difficult time afterwards. Take your time, be a bit meticulous, it'll pay dividends down the road. These are not complicated carburetors.

[WingMan71]

Ok, try to take some picks as ya go if your not familiar with this rack, it'll help putting it back together, especially the adjusters. So many individuals on here have pulled them completely down and then have a difficult time afterwards. Take your time, be a bit meticulous, it'll pay dividends down the road. These are not complicated carburetors.

I will take my time and take pictures as always.  The vast majority of my restorations have been Keihin CV type carbs, not mechanical slide carbs like these, so I'm not as familiar with them.  I took well over 250 pictures of my last restoration, a 1982 CB750C.  Also documented all work in an hourly work log. Such things help prove what was done when time to sell.

I'm worried about setting the adjusters on the mechanical slides. I see absolutely no information in the Factory Service Manual about setting them. Realized what they were when I was removing the nuts from them and they were locked down tight with the yellow lock tite that Honda typically used. Was hoping for at least a description of how to do a bench synch.

That said, I would guess that you can hook up a set of vacuum gauges to the carbs to synchronize and set them as usual.

[bryanj]

From the uk forum in tricks and tips

[WingMan71]

From the uk forum in tricks and tips

Thanks so much for that!  Really appreciate it.

Now, if I just knew what a "tick over screw" was, I'd be in business. 

I'm guessing, by the context, that's UK speak for the idle speed screw?

[bryanj]

The large chromed thumbscrew that raises the tickover speed when screwed in

UK&US two countries sepatated by the same language

[HondaMan]

A useful [maybe] hint: the 350F and 400F carbs don't usually come off the throttle arms until the front mounting plate is loose and tilted forward from the bottom up. This lets the carbs tilt (because their bracket isn't holding them upright) to get the little ball levers out of their lifters.

But...this also often breaks those little flat rubber dust seals on those ball shafts. So, put a bit of lube on those shafts and balls (thru their top caps) before trying to unmount them, or they may/will split the rubber seals, which are now pretty brittle. And unobtanium, AFAIK.

[WingMan71]

The large chromed thumbscrew that raises the tickover speed when screwed in

UK&US two countries sepatated by the same language

I guess my travels around Europe when I was young and in the Navy were insufficient.  I never made it to the UK.

Had I made it there, I might well have learned that "tickover speed" means "idle speed".

I'm a tad embarrassed!