Topic: K4 float bowl vents

[xrrevin]

In beginning to disassemble and clean a set of gummed up 1974 750K carbs, inspection of the "float bowl ceiling" revealed 3 of the brass "baffle float bowl vents" missing.  Two from one carb and 1 from another.

Question:
1. are replacements available (I haven't found any part numbers)?
2. make some and press in place?
3.  run without them (think it could lead to unwanted fuel leakage)?

Suggestions accepted and possibly how any others have dealt with a similar situation.

Thanks, as always, for reading and thinking,

xrrevin

[grcamna2]

In beginning to disassemble and clean a set of gummed up 1974 750K carbs, inspection of the "float bowl ceiling" revealed 3 of the brass "baffle float bowl vents" missing.  Two from one carb and 1 from another.

Question:
1. are replacements available (I haven't found any part numbers)?
2. make some and press in place?
3.  run without them (think it could lead to unwanted fuel leakage)?

Suggestions accepted and possibly how any others have dealt with a similar situation.

Thanks, as always, for reading and thinking,

xrrevin

Do these baffles look like a small brass disc with a little hole in the center and are they pressed into the 'roof' of the carb. body/float bowl area into the beginning of the vent passage ?
I had one fall-out before.. I think they keep the fuel from splashing out of the carb. vents during very bumpy roads.

[xrrevin]

Yes, exactly the situation.  Did you decide to fix, ride and see how things progressed or changed carbs?

Thanks again,

xrrevin

[grcamna2]

Yes, exactly the situation.  Did you decide to fix, ride and see how things progressed or changed carbs?

Thanks again,

xrrevin

I found a set of shallow(Mikuni?)pilot jets,then tapped the carb. bodies and installed them in place of those small,brass discs. I would have rather found the discs,just didn't know who carries them.

[ekpent]

Better try and post some pics to make sure that there is actually a problem or missing parts. Might be normal on the round tops.

[newday777]

In beginning to disassemble and clean a set of gummed up 1974 750K carbs, inspection of the "float bowl ceiling" revealed 3 of the brass "baffle float bowl vents" missing.  Two from one carb and 1 from another.

Question:
1. are replacements available (I haven't found any part numbers)?
2. make some and press in place?
3.  run without them (think it could lead to unwanted fuel leakage)?

Suggestions accepted and possibly how any others have dealt with a similar situation.

Thanks, as always, for reading and thinking,

xrrevin

Post pictures of these "baffle float bowl vents"

[xrrevin]

Thanks to "777" for suggesting pics -- Why? because it made me look at the carbs more closely, and, try to find pics in videos or books to display a bank of 4 carbs together to showcase these brass vents.
  I couldn't find any available pics and I don't know how to put them in the forum anyway.
But, it did make me analyze this situation more completely.  Honda (and other mfg's) will cast a carburetor body with "extra" passageways in it so the carb can fit more applications.  The 750K uses 4 of the same "basic" carbs but #'s 1+2 are drilled for left side and 3+4 for the right (note pilot air screw access is on left side (1+2) and then on right side for 3+4)
  Looking at the carbs from the air filter side, about 1/2 way down the carb body of #'s 2 (on it's right side) and 3 (on it's left side) there's maybe an 8" hose attached to a nipple.  These hoses lead to the float bowl vents.
  If the carb rack is off the bike, with the engine spigots resting on the bench remove the float bowls and floats. Looking into the "roof" of the float bowl area, there are two 1/4" diameter holes about 1 1/2" deep in each carb.  Pressed into this hole at the bottom is the brass "float bowl air jet" which aligns with that 8" hose mentioned earlier.
  Now, the mistake I made originally, is assuming because each carb body has two breather holes that each should also have a brass vent air jet. So, carb #'s 2+3 should each have two, carb #'s 1+4 should ONLY have one each.  The two holes which are the most "outboard, closest to your left foot and right foot" when sitting on the bike are factory PLUGGED.
  Pics would make this info much easier to visualize, so Mr Moderator if you deem this attempt at explanation too "convoluted" you can remove it.
  The fix I'm going to attempt, find a round main jet with a similar hole size and rework the OD for a press fit as mentioned by grcamna2.
  Thanks again, xrrevin 

[newday777]

I understand you on posting pictures on this forum... been struggling with it since joining as I'm not very techie and can't figure out how to make small enough pictures to meet the size limit on here......
I'll be headed up to my shop in a few and look again at your description and compare to the cleaned set awaiting reassembly. I don't have high hopes my pictures will post here still. I tried to get a girl at the phone store to reduce the size but it hasn't worked......

[HondaMan]

Maybe keep this in mind as you study your bowl vents (that's what these are called, BTW): the 2 inner carbs (#2, #3) have the hoses on them, and the discs. The #1 and #4 often do not, because the first one in the pair already has the limiter hole.

Here's how these gizmos work:
The hose is long enough to reach up and over the airn=box to a quiet(er), still(er) zone of air pressure than that which is whipping across the rest of the bike at speed. This is a 'high pressure zone' that is feeding high-pressure air to the float bowls (so they can push fuel up the jets). The disc's little hole is there to limit the turbulence that is no doubt chattering at the end of the vent hose. In the 750K0 model there were 4 such hoses and discs, but starting with the K1 these were reduced to 2 hoses (and their elbows) and the #1-#2 and the #3-#4 carbs were connected together with short brass fittings and short pieces of rubber hose to share 1 of the vent lines to 2 of the carbs. This was both more economical to build (for Honda) and worked better (larger air volume in the bowls to work with, stabilized the mass more).

So...you should find one brass pinhole in each of the #2 and #3 carbs, associated with the little elbows that go to those hoses.

[newday777]

I understand you on posting pictures on this forum... been struggling with it since joining as I'm not very techie and can't figure out how to make small enough pictures to meet the size limit on here......
I'll be headed up to my shop in a few and look again at your description and compare to the cleaned set awaiting reassembly. I don't have high hopes my pictures will post here still. I tried to get a girl at the phone store to reduce the size but it hasn't worked......

Just for those that come across this thread looking for pictures and help on the subjectofthebowl vent brass domes.
I've figured out how to get reduced size pictures from my phone to be able to post to this forum, I take a screenshot of my picture, then crop to the picture (cropping gets rid of excess screenshot shot boarders).
Here are the pictures I took almost a year ago of the carbs I had cleaned and was about to reassemble.
The 2/3 carbs have 2 brass domes, the 1/4 carbs have only 1.
Hope this helps someone in the future that finds this thread using the search function to figure out their carbs. xxrevin did you get your carbs finished and how was your outcome, you didn't reply back to finish your thread(not good to leave threads hanging unfinished...)

[HondaMan]

...and, just to confuse this a little more: the 750K0 carbs have one hose on each carb, with the little elbow and a vented disc in each carb. It wasn't necessary, as Honda found out, so they combined the 2 pairs to save some Yen.

In the PD and later carbs there is just one vent hose and all 4 are interconnected, with just one metering hole.

The main thing is: make sure the hoses reach a still, quiet zone of air somewhere. In racing situations I have seen things like a pill bottle with 2 holes in it, one with the hose entering it and the other open to atmosphere, mounted under the seat. This worked well in the turbulence often found inside roadrace fairings.

[Kelly E]

After installing Mikuni RS34 and RS36 carbs on the KZ 1000 and Suzuki GS 1100E the bowl vent lines accumulated fuel in them. I had them routed up over the the carbs and rearward to under the seat. The RS carbs have two bowl vent nipples on each carb so just underneath the carbs I tee'd each pair together and ran them down under the bike with the overflow lines. To keep fuel from being drafted out I used a hole punch on some Uni air filter foam and made breathable plugs, then rolled them between my fingers like ear plugs to insert. It still vents but doesn't draft any fuel out.

[HondaMan]

After installing Mikuni RS34 and RS36 carbs on the KZ 1000 and Suzuki GS 1100E the bowl vent lines accumulated fuel in them. I had them routed up over the the carbs and rearward to under the seat. The RS carbs have two bowl vent nipples on each carb so just underneath the carbs I tee'd each pair together and ran them down under the bike with the overflow lines. To keep fuel from being drafted out I used a hole punch on some Uni air filter foam and made breathable plugs, then rolled them between my fingers like ear plugs to insert. It still vents but doesn't draft any fuel out.

That foam is a good idea! It would let the pressure accumulate and will also stop some of the turbulence at higher speeds. The later bikes with the PD carbs suffer a lot from errant (or missing) bowl vent hoses or mis-routings, sometimes even dropping their top speed noticeably. That sort of a breather would help.