Topic: Air screw to reduce decel popping?

[PeWe]

I initially thought about this hole. All small holes have a purpose.

[PeWe]

I wouldn’t go digging around in those itty bitty holes with any thing harder than the jets, nozzles, offices themselves are, if I were you..

Especially if your dad hasn’t in the past.. Virgin Honda brass is hard to come by…

Copper and bronze wires can be purchased in thousands sizes like 0.020 for a few bucks at model train suppliers..

Copper is what I prefer because it’s several times softer than brass and bronze..And Bronze is harder than Brass which is what you got unless you have them removed before digging. But look at Delta’s cutaway of a pilot jet in case yours are partially plugged or varnished up to the next smaller size..

Check your timing too.  I like somewhat  advanced initial timing and limited centrifugal max timing. Remember your ignition fires on the exhaust stroke too, so don’t blame it all on your exhaust lighting it off on the deceleration..

Advanced initial timing is a no-no with low octane fuel, but makes for a torquey just above idle launch at the stop sign with premium fuel when trying to tame the open exhaust from the local germaine..

Have you tried premium to see how it affects your deceleration popping..?

Believe it or not, I’ve been running premium since the day I put it all back together. But am now realizing the compression on these engines will never need it. I had a thought that the lower octane may actually make it run a bit better

I can not use the lower octane here. E10 fuel with most likely more water.

I tested when it still was only E5 on my K6 when it had lower compression than today. It ran leaner.

My K2 had 150-160PSI with fresh stock size pistons.
Same tester showed 170-175PSI with CI +0.50mm K7 pistons.
So Shell V-Power to that bike too. Like my car and K6.
It had the severe throttle off popping with Shell Power and 086A carbs that must be dirty inside.

I'll focus on popping sound coming season.  It had a little of it.
 If fuel additive will help. Stronger dose. If not, air channel to clean.
Last season was jetting of the  064A carbs and tuning of the charge regulator.
Add a voltmeter you can look at when riding will make you to adjust to >14V when fully charged around 4000rpm or before.
Not >14.5V that easily will become >15V. I have adjusted some on both my bikes and 3 regulators.

[Bigmant]

UPDATE! And interesting knowledge.

So I’ve taken the carbs off. And discovered some interesting things. You can see in the picture below, the Honda made rubber insulator is a different type of rubber than the cheaper version from 4into1. Important to note, 4into1 sells both. I just happen to get mine from south bend Honda.

They both are equally malleable, there are no cracks on the cheaper ones, but Honda’s are numbered for the cylinde and there is a different sheen of rubber. If you’ve ever watched racing, you’ve seen how fresh tires always look more shiney? That’s how the cheaper ones look. So perhaps that makes the genuine Honda seal better? We’ll see.

Next, the 4into1 replica insulator clamps aren’t adequate. I can pull the insulators off when they are as tight as possible. Unlike a normal circle clamp, you can only get either genuine Honda or replica’s so tight before they bottom out. So I’ve ordered some normal circle clamps from Carpy’s that fit the insulator ring. That should help seal them up better.

I also took this opportunity to clean all the holes with a small gauge carburetor tool I bought on amazon. All the holes were clean, which was not surprising, but rules it out. I also found most of the floats were out of spec, and were filling up the float bowls too much, which as I understand it can cause a too rich condition. So now in spec at 26mm should help as well.

Lastly! Some interesting air screw findings for those that don’t know this. First picture is at fully seated minus 1/8th. You can see that the hole of the aircrew is perfectly aligned with the air intake hole on the air filter side. The pictures after that are 1 turn less every picture. Passed 3 turns, the hole isn’t visible any more. I didn’t know that’s how the screw worked, so it was interesting to see.

More to follow as I get new clamps and take it for a test drive. We’ll see if this fixes the popping and what I think was ultimately the bike running too rich.

[Don R]

 The worm screw clamps can bite into the rubber and cause it to bunch up as it tightens, I have some thin aluminum flashing (or pop cans) material that I use scissors to cut shims from to slip under the clamps. I got some aircraft type clamps that also have a built-in shim behind the worm gear slots for my turbo connections.

[Bigmant]

I’m also going to post this here because it makes SO much sense. I was never a believer of how important the float adjustment was, because I figured it was a glorified toilet bowl stop. But not the case! Enjoy:

Think of it like this, when you put a straw into a glass of liquid the liquid tends to rise up the straw because the other end is open to the atmosphere. The hight that it rises to is due to atmospheric pressure acting upon the surface of the liquid and the specific gravity, so to speak, of the liquid itself. The same goes for the needle jet in your carb. To some degree, i have no idea how far, the fuel will rise inside of the tube. This effectivly decreases the distance the fuel has to travel to enter the carb throat. With this in mind, if the distance the fuel has to travel to enter the venturi is less, more fuel can enter the combustion chamber for a given amount of vacuum. Just the opposite is true for a lower volumn of liquid in the float bowl.

[scottly]

Off topic posts will be/have been deleted from this thread.

[Deltarider]

[...]
Lastly! Some interesting air screw findings for those that don’t know this. First picture is at fully seated minus 1/8th. You can see that the hole of the aircrew is perfectly aligned with the air intake hole on the air filter side. The pictures after that are 1 turn less every picture. Passed 3 turns, the hole isn’t visible any more. I didn’t know that’s how the screw worked, so it was interesting to see.
[...]

The position of that (crossdriled) hole in the airscrew in relation to the inlet hole in the mouth of the carb is irrelevant. Mixture is only defined by how far out or in the airscrew is.

[newday777]

I initially thought about this hole. All small holes have a purpose.

Per
I just had to derack the right 2 carbs off a set of K2 carbs that I thought I had cleaned fully because I couldn't get the clear tube test levels to change blowing into the right atmosphere breather tube like the left side did on the test rack. The #3 carb I had to pull out the 90° elbow to fully clear the old dried MBTE white dust buildup. What a pain this set has been because of it.
A set of used steel guitar strings is a must have tool for cleaning it out of the various ports. The emulsion air feed tubes and the bowl drain holes as well as the main and slow jets were plugged solid with the old white dust that 3- half hour runs through the ultrasonic cleaning didn't touch.
Hondaman really explained it well in his book. A great resource if anyone is working on these carbs that had gas left in them for years to dry out being exposed to high ambient moisture. The bike sat in an unheated, un air conditioned museum with less than 10,000 miles on it, last run in 2014. American ethanol gas of the 90s and 2000s really did a lot of damage. See the before pictures of the carbs to know what to look for and expect it to take a lot of deep cleaning that spray cleaning/ultrasonic cleaning just won't be sufficient to get them clean.
The tank has pin holes too, also from the moisture that was on the top seam down from the filler cap, that I found while derusting the tank last year.....
I even found a cracked bowl overflow tube yesterday and had to solder it to fix it. No more leaks now on the test rack. All the bowls and brass is polished up too.
Today I hope to get them run on one of my bikes and do a vacuum sync on them before sending them on to my friend.

[PeWe]

Fishing line might work too in that air jet? A little bit softer, not scratching.
Followed by chemicals and compressed air.


A good reminder before mounting the carbs on bike.
And when stock airbox and bowls are off.

The upper vents another holes that can clog.
If fuel in both bowls will bubble and overflow when blowing in the vent hose, it must be good.  2 hoses, 1-2 and 3-4.

[Bigmant]

Fishing line might work too in that air jet? A little bit softer, not scratching.
Followed by chemicals and compressed air.


A good reminder before mounting the carbs on bike.
And when stock airbox and bowls are off.

The upper vents another holes that can clog.
If fuel in both bowls will bubble and overflow when blowing in the vent hose, it must be good.  2 hoses, 1-2 and 3-4.

For everyone’s awareness, here’s the small hole carb cleaning tool I bought. $5.99 on amazon and it works great. It fits in all these vents we’re talking about.

https://www.amazon.com/gp/aw/d/B09TW6L7J8?psc=1&ref=ppx_pop_mob_b_asin_title

[Bigmant]

Alright guys I need some help!

So I now have genuine Honda insulators, circle clamps so that there is for SURE no air leaks. And the exhaust is definitely tight.

I found that the floats were not to spec. In fact all four were quite high (my fault from when I first set them up.) They are now in spec at 26mm.

I lowered the main jet from 140 to 130. And now the bike runs like it has no guts. First gear HEAVILY lags. Like it has no power. As in, if I let the clutch out too quickly it’d stall. Any thoughts of what I’m doing wrong?

Here is the setup:
The new setup is as follows:
#130 mains
#40 idle jet
Needle jet at the lowest setting (most rich)(5 from the top)
Air mixture screw two turns out (more out made it run slightly better)
4-1 Carpy’s Yoshimura style exhaust
4into1.com pod filters

[scottly]

What do your spark plugs look like? Please post pictures. Also, please post pictures of your pods.

[Bigmant]

What do your spark plugs look like? Please post pictures. Also, please post pictures of your pods.

Does that show it well enough?

[scottly]

I can see the pods. Now, how about the business end of the spark plugs?

[scottly]

Air screw question here. I’ve got a 4 into 1 exhaust and pods. The bike has great power and is synced well. But under power on deceleration, there is quite a bit of popping I’d like to see if I can clean up.

Wait a minute. You went from great power to no guts, from trying to stop minor popping in the exhaust on deceleration?? Somewhere along the way, it seems you may have fixed the bike until it was broke.

[Bodi]

"you may have fixed the bike until it was broke"
Kinda unnecessary, that.
I tuned my 400F carbs with a Yoshimura 466 kit, Yoshima street cam, K&N pods, and Kerker 4-1 exhaust to run pretty good. Probably someone will attest that this is not possible, but I'm happy with it.
I do not agree that "Honda achieved perfection and you can't ever exceed that". Yes the bikes ran great as stock (excepting the super lean EPA crap they were forced into) but let's see what we can improve.
There are 5 carb variables, 6 if you include float adjustment (I did not, set it to service manual spec): Main Jet, pilot jet, airscrew, needle clip position, and needle taper.
There's a chart showing their interactions and the throttle ranges that each predominates. Definitely study that.
I could get pretty good tuning with just #1 to 4 but still had flat spots etc. - setup involved many plug chops - and practice getting the carbs off and back on rapidly.
I had full throttle with a good plug colour, pilot jet and airscrew OK for good idle mix (rich for decent off-idle throttle, 400 has no pump).
Main jet got bigger as expected with better breathing, pilot jet got smaller (can't explain that).
I made a scale marking thing for the throttle with 6 or 8 points from off to WOT. And marked the needle and measured where each stop left the emulsion tube and calculated where it was in the main jet for each mark.
Then a series of plug chops and clip adjustments so only OK or lean conditions were present.
Plug chops recording the colour at each marking.
Removed the needles and used a drill press and brasso on a cloth to thin down the needles at the lean zones to thin the needle to increase fuel and go richer.
Several iterations of this and I had decent mixture for the full throttle range, more or less.
Bike runs really well in my opinion. Some stumble off idle if the throttle is opened abruptly but I don't know of a carb bike with no accel pump that doesn't do that.
Would it be easier with a A/F meter and dyno? Yes. I did not have them. Maybe not much easier though , and if you're paying by the hour... $$$$.
Do I recommend this? NO!!! I was young, stupid, and had way too much time on my hands, and easy access to roads where I could do plug chops without attracting police interruption. I don't think such roads exist within two hours of me now.
A modern bike where this kind of tuning is done with a laptop, AFR meter, and a dyno... takes the romance out of it IMO.

[Deltarider]

Compliments Body for that post and your honesty expressed in the last lines. Good to remind us that this forum is as much about our bikes as about us.

[PeWe]

Reminds me about next plug shop coming spring or at least main jet check on my Blue K6 970cc.
WAT check from 180kmh to verify the response is as it has been before at its best. A clear acceleration, not only more screaming.

I reduced pilot jet and fuel screw to solve minor too rich at slow throttle roll-offs at 80kmh and less on 5th gear, only possible to notice downhill.

Fixed that so the total amount of fuel reduced so I had to raise the needles 1/2 notch by a washer. Better.

MJ increased one 2.5 step which made it better, no pinging as I heard earlier at WOT,  pinging at 7000 rpm on 5th gear.

Season ended Oct 20 so high speed check need another test.
I have roads for it but it is always a tingling feeling before a main jet check in high speed.
Another thing when higher speed just happen

I have reduced the acc pump stroke due to much black smoke at idle revving this winter. It was at max setting.

So the throttle response 100-160kmh (needles) and from 160/180kmh have to be redone.
Plus cruise in 140-150 kmh for a few km to read the outer plugs I can reach on a hot engine.

MJ test by cruising to at least 200kmh according to speedo plus WOT, there a slow throttle roll-off to feel if bike will accelerate during roll-offs (lean) or just slow down (OK).
If hearing a  d-d-d-d sound, too rich.

I verified needle cruising last ride not too rich. (100-160kmh small throttle increase followed by roll-offs, in steps up to 160kmh.)

Typical for carbs when they might be perfect. It is needed to continue until it runs bad to clarify it was good before.

The only question left is:
Can I raise the needles 1/2 notch and/or increase main jets another 2.5 step?
It can be good as is too;D

Both have been too lean before the last 2 rides where I adjusted needles and MJ richer and better.

I have been in situations when doing MJ tests. Slow going cars driven in 60/70kmh on a 80 signed road will suddenly pop-up in my face behind a corner or uphill when riding above 160kmh.
I thanked myself for the working dual front brakes making front tire to squeal.

The legal speed area can be tricky to get right. But most important. Not fun to ride when that is not ok.
More carb rides done, more small errors you will notice.

[scottly]

"you may have fixed the bike until it was broke"
Kinda unnecessary, that.

Bodi, read the first post on this thread.

[scottly]

Here is a thread from the OP's previous tuning efforts, when he first settled on huge 140 mains:
http://forums.sohc4.net/index.php/topic,190368.msg2215989.html#msg2215989

[Bigmant]

Here is a thread from the OP's previous tuning efforts, when he first settled on huge 140 mains:
http://forums.sohc4.net/index.php/topic,190368.msg2215989.html#msg2215989

The bike ran MUCH better then haha. Which doesn’t make sense because the setup now should be far superior. Fixing air leaks alone should have made the bike too rich and therefore meant the main jet size reduction was justified.

It just doesn’t make sense why going down to 130, which is still very big, makes it run worse. Based on some other posts, a +6 size increase over stock should be more than adequate.

[scottly]

I found that the floats were not to spec. In fact all four were quite high (my fault from when I first set them up.) They are now in spec at 26mm.

By "quite high", do you mean the measurement was less than 26mm, and if so, how much?
BTW, some popping in the exhaust on decel is perfectly normal; it's just more noticeable with an open exhaust than with the stock mufflers.

[Bigmant]

I found that the floats were not to spec. In fact all four were quite high (my fault from when I first set them up.) They are now in spec at 26mm.

By "quite high", do you mean the measurement was less than 26mm, and if so, how much?
BTW, some popping in the exhaust on decel is perfectly normal; it's just more noticeable with an open exhaust than with the stock mufflers.

Probably in the range of 28-30mm if I had to wager a bet.

[scottly]

The larger measured distance meant a lower fuel level in the float bowls, causing a leaner condition, and may have explained the large main jets? I asked on the other thread in 2022 if you had performed a "clear tube" test to check the actual fuel level in the bowls, and I would recommend doing it now. Do check the spark plugs: if they are black and sooty or black and wet, the current setup is too rich.

[PeWe]

I had issue with fuel hoses that were slightly kinked. It caused fuel starvation in higher speeds.
Where the fuel connection is, in wrong angle.