Any way to clean or repair air cut valve

[dpcarson]

I have an aircut valve with the slightest little bit of leak.  This is on a bike that sat up for 5 years.  Is there any cleaning that can be done to the valve or is it an automatic replacement?  I had another one doing the same thing.  Squirted just a dab of sea foam deep creep in it and blew it out and then it started sealing right.  Just wondering if this is a legitimate fix or just a temporary patch and the problem is going to show back up soon.

Thanks

[da prez]

  Sea foam probably caused it to swell and seal. I do not think they are repairable.


                               da prez

[NE_Valk]

How do you know if you have a leak?  Sound?

[Ricky-D]

The air cut valve is not a necessary system for the good running of the engine.

The engine can run just as well with no air cut valves at all.

With this in mind, I suggest to do nothing, or block it off.

Naturally, this is my opinion only.

You should do as you feel you need to do.

***

[dpcarson]

How do you know if you have a leak?  Sound?

I know it had a leak by applying vacuum with vac tester and then pressurizing and seeing pressure drop.

Thanks Ricky D.  If it doesn't affect the system and how it runs, then why spend the money.

[WintrSol]

Without the air cut-off valve, you may get after-burn (popping in the exhaust) during engine braking. Not harmful, but it can be annoying if you have louder than stock exhaust. Some people like that sound. The valve reduces the air going into the pilot jet system, so enriches the mixture during high vacuum, when it tends to become lean.

[dpcarson]

Without the air cut-off valve, you may get after-burn (popping in the exhaust) during engine braking. Not harmful, but it can be annoying if you have louder than stock exhaust. Some people like that sound. The valve reduces the air going into the pilot jet system, so enriches the mixture during high vacuum, when it tends to become lean.

Good info, thanks.  As long as I can get her back to running right without pulling the carbs again, I think I will just leave it on at this point.  Still can't get than dang #4 cylinder working. 

[98valk]

detailed info

https://www.motorcycleproject.com/text/aircut_valve_more.html


A failed aircut diaphragm will pass fuel across the vacuum barrier and directly from the idle jet into the carburetor bore, resulting in gross richness at idle and low speeds. A diaphragm is failed by merely having a crease in it, which in short order will become a hole, as the very active valve opens and closes each time the throttles are opened. What's worse, all replacement aircut diaphragms are inferior to the (unfortunately unavailable) factory original because they are made cheaper and thus are more prone to failing.

So defeating the aircut is preemptive maintenance. That's it. There is no performance advantage, or disadvantage. Defeating the aircut does not solve any problems, or create any. The procedure does not change mixture strength in the idle circuit, or any other circuit. It does not require a compensation elsewhere in the carburetor (at least none you shouldn't have already done irrespective of the procedure). Don't look to an aircut defeat to correct a poor idle, that problem is due to many other possible issues. Don't look to it to improve fuel economy. Don't expect it solve anything at all. It won't. It can't. It isn't meant to.

Bypassing the system is as simple as blocking off the vacuum source, the valve's trigger. Do this by substituting a solid piece of rubber in place of the tiny o-ring at the vacuum port. Leave the diaphragm in place even if failed, as in all cases it serves as a gasket for the aircut valve cover, and in some cases is also needed to keep the aircut valve open.

[hubcapsc]

Air cut valves show "in stock" at partzilla for $70  each. I'm
sure they  have a purpose. I guess it is to prevent the backfires
that people talk about on forums, I don't see any place where
Honda says one way or the other, though I have a book at home
I could try to look it up in.

My buddy Kent, who hates strawberries and probably hasn't eaten
one since sometime in the 1960s (if ever), corrected me once
when I warned someone that they "didn't want to eat wild
strawberries with yellow flowers, just the white flower kind".

Perhaps Kent is right: the yellow flower ones won't kill you, but
trust me, only eat the white flower kind  ...

-Mike

[Calboy]

  Sea foam probably caused it to swell and seal. I do not think they are repairable.


                               da prez

"Okay, I am putting this in two places, and on other sites, as I don't know where it should officially go, but i want as many peeps and homies as possible to read this. I got totally bugged out , becuase so much speculation was going on here, with the one thread being 23 pages long, and 4 years old. I couldn't stand it anymore, so i called Sea Foam.
I was transferred to Jim Davis, Technical Director/ Research, of Sea Foam. and we had quite a cordial conversation, a real easy going guy, he is college educated, with a degree in automotive technology, has 35 years experience in the automotive repair industry , and is an A.S.E. certified mechanic. He has been with Seafoam, I think, the last 5 years, as his doctor told him, his body was just too out of whack, to handle mech work anymore.
So I will try to write as much as I remember, from my chicken scratch.
First off, I asked all the questions I wanted, such as , will it hurt, is it damaging to any parts at all, can it be used as maintenance, what do you do after you use the product, does anything need to be changed out, etc., etc.
First, he stressed multiple times, that this was a 100% petroleum product, nothing else. He said this many times during our conversation. he said there is nothing added, no fillers, no astringents, no mulsifiers, cleaners, detergents, nothing at all.
so how exactly does it work? Well , as you know, there is more than just carbon in your engine, there is salt , sulfur, all kinds of vox, and nox materials, you name it. How does it get stuck in there, and not filtered out? Simple, alot of the stuff we normally add, including gas, has a certain amount of sludge, varnish, lacquer, and gums added to it. This is the stuff, that sticks to walls, pistons, etc., especially when cooling. then all the other stuff we talk about, including carbon, gets stuck to this stuff, carbon, small micron stuff, other nox and vox particles.
Seafoam attacks and disolves the varnish, gum, sludge, and lacquer in there primarily, and then begins to break up , the other stuff.
Once this happens, all the junk is now freefloated back into suspension, and can be filtered out, or burnt out, of your various systems.
Seafoam does 3 other things primarily; controls and locks up moisture, adds lubricity without viscoscity, and cleans without adding any chemicals at all.

Does it harm other materials? In a word, no. He told me that right now, around their research area, they have multiple glass , sealed jars of Seafoam, with various things in each jar. plastic, rubber, seals, o-rings, pencil pieces, paper clips, bits and pieces of everything. Some of the items, in some of the jars, have not been opened or disturbed for 3 plus years now. he said, these bottles and items are studied through mag glass, and items looked at closely through microscopes, with no apparent natural destruction, loss, or dispersal,or disfiguration, becuase the item was sitting in Seafoam.
So you do not have to worry about your gaskets , seals, o-rings, etc., from exposure to seafoam.
he also said as a former tech, he did this same cleaning job many, many times, to multiple autos, and only one time did he have a problem.
It was with a car, driven by an old dude, who never drove it over 45 miles per hour, never put it on the highway, never got it hot, allways in traffic/city driving, and never driven over 20 miles, in either direction. he said it was just so full of carbon and junk, that the gum/lacquer did get on his 02 sensor, and a chunk of carbon did stick to that. he replaced said o2 sensor, and did another cleaning job, and the car drove like new. he said the old dude was so
impressed , because it drove the way it did , when he bought it new. "

[WintrSol]

98valk is correct; disabling the air cut valve has no effect on performance, at all. It's only function is to reduce the exhaust pops on decel, some of which can be quite loud. The diaphragm in the valve can cause a performance issue, if it starts to leak. If you don't mind the exhaust pops, and you are working the carbs anyway, you may want to just disable the valves, so they can't bite you if/when they fail. At $70 a pop, you know I won't bother with new ones. Especially if one has failed, how long before the other 5?

[98valk]

98valk is correct; disabling the air cut valve has no effect on performance, at all. It's only function is to reduce the exhaust pops on decel, some of which can be quite loud. The diaphragm in the valve can cause a performance issue, if it starts to leak. If you don't mind the exhaust pops, and you are working the carbs anyway, you may want to just disable the valves, so they can't bite you if/when they fail. At $70 a pop, you know I won't bother with new ones. Especially if one has failed, how long before the other 5?

Just so we are on the same page,
from the site that I copied from, "A failed aircut diaphragm will pass fuel across the vacuum barrier and directly from the idle jet into the carburetor bore, resulting in gross richness at idle and low speeds."
So a failed leaking one does cause a problem/performance loss which would be a stumble off idle and low cruise speeds and lower mpg.
But yes, disabling a perfect working one does not have an effect on performance in anyway and reading through his site would require extra tuning of the pilot/idle circuit. most likely as easy as opening up the mixture screw 1/2 turn.

[YoungValkFan]

Sorry to revive this thread, but there is quite a bit of contradicting arguments about these stupid little valves. My bike has been having the forsaken stumbling off throttle and at low speed cruising and I'm coming to the conclusion that it is the air cut valves. I have gone through every little thing else that it could be: carbs are clean as a whistle, vac caps are brand new, stock air filter and jets with cobra pipes (previously had 38/110 jets).

I dont mind the popping, in fact, I kinda like it. What i don't like is the problem with engine performance others have cited here and elsewhere. Mine seem to have catastrophically failed. I am therefore prepared to bypass them entirely, but I'm confused as to whether that is possible with valves which are malfunctioning as bad as mine are.

Any thoughts?

[mello dude]

Are you guys talking about the PAIR valve pump.... this thing?

[Icelander]

Are you guys talking about the PAIR valve pump.... this thing?

Nope. Had to go look this up as well since I didn't know what it was.
It's #24 on this pic and there are six of them...

[Mooskee]

 had this from where I explained it to someone recently.



Here are pics from Partzilla.

[RonW]

It use to puzzle me why lean fuel ration would pop in the exhaust. Logically, rich fuel mixture would do that instead via some of the rich fuel not igniting in the cylinder and the residual fuel escaping into the exhaust. There on the exhaust walls would ignite the residual fuel.

• Apparently, when the fuel-to-air ratio is too lean due to deceleration, there's not enough fuel in the mixture for it to combust in the cylinder but enough fuel in the unburnt mixture to combust (pop) in the hot exhaust.

[Mooskee]

This forum thread discusses blocking the ACV tubes using a BB, or an Airsoft pellet.

http://www.valkyrieforum.com/bbs/index.php/topic,114893.0.html