rebuilding carbs

[exvalvesetdabbler]

There is no ovality on the needles, which is why I suspect corrosion has had a hand in what happened.  Looking at the outside of the tubes there isn't any corrosion/putting that would set off alarm bells, hence why I originally reused them in 2010.

Fortunately the 'come in handy box' delivered and I have 6 good tubes to play with.

Regards
Dave

[Oddjob]

I happen to have a bag in front of my keyboard full off all the brass out of a set of 550 carbs. So I thought I'd try this and see what the result was.

Completely different. None of the needles went down fully, in fact they stopped well before the grooves, plus even in that position they were really protruding past the end of the emulsion tubes. It seems the 500/550 needles are considerably longer than the 400s. You'd expect they'd be similar, same style of carb so why are the 400 needles so short? How do they interact with the main jet when they don't protrude past the end of the tube. Have you checked the number stamped on them to see if they are standard? maybe someone swapped them in the past out of a different Honda.

[exvalvesetdabbler]

I have about 8 of them, the good 4 were run in the bike when diagnosing the original problem.  I then bought 4 honda needle sets (they were reasonably priced at that time)and installed them. They were all the same length/taper.  The good 4 came from a wrecked bike that I bought for spares in 1987. The carbs hadn't been messed with apart from chewed up drain screws.

I can't see any keihin logo on either the tubes or needles. The needles have 18234 etched around the top just below the circlip groove.

Regards
Dave

[exvalvesetdabbler]

[ Guests cannot view attachments ]

Looking at Keyster documentation they have 18234 annotated next to their D22-S(standard) needle which might be a clue.

Regards
Dave

[Oddjob]

On the web they reckon the standard needles as fitted by Honda were marked D22. As in all things that's subject to be wrong. Shame I can't find the same tables the 500/550 has for all there markings.

[exvalvesetdabbler]

D22 is the Keyster part number.


Here for the 550
https://www.jp-stores.com/mc/we70630/?c=329&show=20&mode=&keyword=&p=1

I have never found a better resolution image for these kits

Dave

[exvalvesetdabbler]

When setting float heights, honda doc's always shows a round bottom float so it's obvious where to measure from   The 400 has flat bottom floats, so should we measure from the highest point or the middle? Maybe a dumb question but someone has to ask it.

Not knowing I have always gone middle before to edge my bets on previous builds

Regards
Dave

[exvalvesetdabbler]

Another kind of question regarding the small black bits that hold the float valve bodies in place.

[ Guests cannot view attachments ]

The clip is slightly curved, they all are. The above image is one resting on a bit of tool steel.

My assumption is that it acts as a dished washer and the prongs bear down on the center of the valve body to keep it in alignment rather than on the edge off center.  Installing it wrong way up could result in the valve body not sitting straight in the carb body.   Does this make sense?

Regards
Dave

[Bryanj]

I always took as keeping pressure on the brass

[exvalvesetdabbler]

Final assembly completed

Installed all the brass ware, throttle sync adjusters and fuel interconnectors.

Carried out a bench sync

Set the float heights. A couple of floats were not sitting right on a flat surface so they were straightened first

[ Guests cannot view attachments ]
A bit of work to do here looking down the line of floats. Swapping floats can even things up a bit before adjustment.

Using my float guage set at 21mm. It was still in the box of bits so that saved making another one.

[ Guests cannot view attachments ]

Final check using the Vernier calipers

[ Guests cannot view attachments ]

Just need to source some tubing for overflow and breather and we should be good to go.


For interest, here are the o ring sizes I used. IDxCS

Float valve 5.5 x 1.5
Main 4.1 x1.2
Fuel interconnects 6 x 2
Bowl 63.2 x 1.9
Drain screw 5  x 1.8

Regards
Dave