Topic: On elevation and drilling out emulsion tube holes.

[Soos]

Yes I have read the Thoughts by hondaman FAQ(great FAQ BTW), and the one on carbs a couple of times now.

I thought I had done everything to my carbs that might be done and still run right.
Upon re-reading the FAQ's early this morn' I read about the emulsion tubes holes being drilled out for bikes being run at altitude.

Well, my elevation of 4,549 feet (1,387 meters) makes me think of drilling the emulsion tube hole pattern/hole sizes out.( my elevation is close to Denver CO.'s 5200'ish)

I was thinking the 0.040 holes seemed a bit overkill(as stated in the FAQ), but the FAQ stated drilling the top 2 rows or four holes out to 0.04.
My emulsion tubes have only 1 row of four.
the other 5 rows only have 2 holes each.
All holes have 0.026 holes in them stock.(0.635mm)
(BTW, this on a '79 CB650)

I am thinking of going to:
1st  row 4 holes at 0.036 holes
2nd row 4 holes at 0.036 holes
3rd row  4 holes at 0.030 holes
4th row 4 holes at 0.025 holes
and leaving the 5th, and 6th rows alone.


Am I possibly going to small on the diameter of the holes?
Could I be wanting to add to many holes?
I do have 2 sets of emulsion tubes to play with.
I would like to do 2 slightly different patterns/hole sizes, and try them both to see if there is a benifit from one over the other set.
But I **REALLY** don't want to go too far and scrap a set. I can always go bigger/more holes, but not smaller/less holes.


While I got your attention.... Is there a benifit to drilling the idle jet emulsion holes as well?
And (sadly) no, I don't know the pattern on those, as I was afraid of pulling them on my last carb cleaning/modification.
Although I feel like I NEED to at least pull them and clean out the emulsion holes.(is that the right term for those holes??)

Alright, i've packed enough questions in here....


l8r

[Soos]

One last question.

Would it make ANY difference if these holes were drilled at an angle?
For example aiming the drilled holes toward the jet, or the other end of the emulsion tube?


thnx,

l8r

[Jonesy]

I've tried the emulsion tube mods and so far I like the results. (I'm much lower to sea level, so I only drilled half of the bigger holes). The acceleration seems smoother and so far, the plugs like the change. Of course, I have an extra set of emulsifer tubes to fall back on...

The best advice I can give is to go slowly, just slightly enlarging the holes little by little, and only start with 2 of them, until you get up to the largest number drill size (0.04) After every change, keep peeking at your sparkplugs.

Mark (HondaMan) can probably give you a better idea of where to start...

[Soos]

Well, on reading other posts on drilling out emulsion tubes, (unless i am rembering wrong) it has been stated going
too big will get no better results, but will cause no ill effects.

I have drilled one set out already.
However instead of my origional thoughts of adding all those holes I opted for drilling the top row out to 0.036, as well as adding 2 holes on the next row(0.036) and drilling out the two existing ones on the second row as well.
I left all the other holes at 0.026, but did add 2 holes between the 3rd and 4th row 90 degrees off from the other holes.
I drilled those at 0.026 the same as all the other stock holes.


My initial test ride was nice.
It does seem a bit more responsive than before from 1/4 throttle to WOT.
However, it may be nothing more than wishfull thinking.(still need to go bigger on the mainjet though)

I'm not too sure standard tuning mods are going to hold too true with what I have done to this set of carbs however.
Having drilled the air passages that feed the slow jet, and main jet has given me some headaches tuning these carbs.
Due to having enlarged these air passages, I am leary about going to big with the emulsion tube holes.

D@mn.... forgot to pull the idle jets out (pressed in pieces of sh..) and see if the emulsion holes are clear there...pretty sure they are... but i dunno.

I also set my floats today to match the lowest of the 4.(unless i overcorrected)
They are ALL set beyond book specs. I'm not sure if you would call them lower or higher, but the gas level in the bowls is lower.(making it run a bit leaner)

The more I tune these carbs, the closer I get to the milage I was getting last year.
First 60 miles resulted in 22.5mpg.
next 75 miles got me 23 MPG.
the last tank got about 35mpg.
just filled up today, and have gotten 45mpg.
Last year, the best i could get was 60+mpg.(and that was driving nice and aesy, under 55 the whole tank)
I'm anxious to see if the emulsion tube mods do anything benificial to my MPG.

The only major benifit I have noticed with the mods I have done so far(besides the mass amounts of tylenol i consume to kill the headaches) is i no longer have to use the choke.
I have been able to start her in as cold as 32 F. weather.(took cranking twice, for 10 seconds each,  but she did it)
If it is over 45 degrees, she starts every time within 1-2 seconds.
NICE.

l8r

[HondaMan]

Like Jonesy said: go at them a little at a time. I have not done a 650, but I think my brother did his, back in the 1980s. He liked the 500 I had, which had this mod. His 500 didn't, to my knowledge.

If you go too far, you can solder them shut and go again. What happens on "too far" is this: no further changes. It just gets better to a point, then doesn't get any better. Drill the holes straight across, from one hole to its mate across the tube. Keeping them square is somewhat important, as this makes them bubble better than angled holes would.

The idle jet doesn't usually require it, because opening the air screw causes more agitation, which is how it leans that mixer out.

[Soos]

I got into her again last night.


Pulled the slow jets, and low and behold, I'm not sure why the bike could idle.
Three had most of the emulsion holes plugged 75% or more.
Idles just a hair over 1000 instead of a bit rough at 1300 now!

While I was at it, i re-checked all passages i could access without separating the carbs, and found that my accel pump passages were severely blocked...
So I swapped the bowl setup from my spare set.
I figured, it worked well last year and those passages were not blocked, so it can't hurt.


WOW... it ran good before, but the throttle response is WAY better now.
VERY crisp in the midrange now.
can't beleive I missed the accel pump passages being blocked when i rebuilt them...
And taking the pressed in slow jets out, and replacing them was way easier than i imagined.

Sometimes i feel like a fool, other times I know I am

I think I have gone far enough on my emulsion tubes....
I will mod. my unmolested pair, and I am thinking instead of going bigger holes, I will add more small holes.
none any bigger, just more, 4 - 0.026 holes on all 6 rows.



l8r

[Pinhead]

I did the emulsifier holes in my 650 last fall and it seemed to help throttle response/power. I've got one question for you, though..

What is the proper method of pulling the pressed-in slow jets? I'm having a bit of trouble getting my bike to idle smoothly until it's warmed up really well. It was 90F out today and I had to choke it to get it to start, so I'm guessing there's something going on...

Also, how did you clear the accelerator pump passages in the carb bodies? I got the pump itself to work in the bowl, but I think the tubes are clogged in the carbs themselves. Do I have to separate the carbs?

It's good to know there is a fellow CB650 owner with some of the same questions that I have.

[Soos]

Well, as for pulling the pressed in pilot jets, I took a pair of pliers and grabbed it in line with the jet itself.(as low on the jet as possible, and still have twisting room)
A slight twisting action, and pulling at the same time popped them WAY easier that I thought they would be.
Mind you that was after removing the float and mainjet/emulsion tube.
To replace them after cleaning, I used a 4oz ball pen hammer on the face of the jet, and tapped that with a brass mallet.
I did this in an attempt to keep from marring the face, or distorting the opening by hitting it with the hammer directly.
Anything along that line of insertion would work IMO. As long as it will not leave any bits in the carbs(I'd shy away from using wood, and if you do, use hardwood)
Just be sure to look all aroung the base of the jets to ensure there is no gap, and they are seated fully.


As for the accelerator pump lines, when I had them torn down I used compressed air to check the lines.(after spraying some brake cleaner into the passage, when I blew the air into there, I could see spray coming out of where the accel pump sends the gas)
My carb bodies had clear lines, but the bowl assembly is what had given me problems.
If you have clogged accel pump lines in the bodies themselves, I would try to use a strand from bicycle brake/shifter cable and some carb cleaner/brake cleaner spray. Or carb dip if doing a complete teardown.
You might be able to snake the strand of cable up through the accel pump passages.
If not, you might be able to get at them if you only seperate the 2 pairs of carbs, instead of a complete teardown.



What did you drill your emulsion tubes to?
Did you simply enlarge existing holes, or add a few?


l8r


P.S. - What elevation are you running at as well?

[Pinhead]

I took the smallest drill bit that I had that would make a slight change. I don't really know what size, but it did help. I enlarged all of the holes, but didn't drill any new ones.

Is the idle jet/emulsion tube all one unit, or are they separable? If they pull out that easily, I guess it couldn't hurt to pull them and make sure all of the holes are clear. All I've done is make sure the jets themselves are clear, but there is no way to insure the idle emulsion tubes are clear without pulling them...

I'm in Kansas City, but I don't know exactly what the elevation is.

[Soos]

Well you are at roughly 758 foot, if you ever wanted to know... That is if your in KC Missouri.

And yes, the emulsion tube is non-removable from the slow idle jet.
On the '79cb650 it has 4 holes...
a pattern of two, then 90 deg. off of that a little lower, another pattern of 2.
 darn, forgot what size the holes are....
0.026? (#71 drill bit) If I rember right.

When I pulled out the idle jets, there was a bit of gunk on them, and a few holes partially clogged.
Nothing too bad, but after cleaning them, it allowed my bike idle about 250 rpm lower reliably.

l8r