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I need to find someone who understands the fuel injection system on my LTD. I am a fairly decent mechanic, and have most of it figured out, but the part I am having trouble with is still a mystery to me. The manuals tell how to take it apart and put it back together, but they do not explain how it works. I do not have the genuine Honda manual.

This is about the reed valve system. It is a very simple design, at least until it reaches the AIR valve. It is a completely vacuum operated system. The AIR valve has a single wire attached to it, which appears to go to the ECM. Without this system, even with all the vacuum fittings plugged and the wire disconnected, the engine will not run below 3000 rpm.

My reed valves are bad, and I cannot find any more. Can someone explain to me in detail exactly what this system does, and is there any way to bypass it?
 

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How was the bike running prior to this? I thought I had problems with my air valve, even replaced it and finally manually reduced the idle and I had no more problems.
 

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The bike was running fine, but was making a squeak squeak squeak noise as it ran. I searched everywhere for the source of this noise, and finally found it. It was the reed valves. There is a short rubber hose which is MOLDED onto each reed valve assembly, and both of them had deteriorated to the point where they had cracked and split. The noise was coming from a pulsed vacuum leak at each reed valve.

The system works like this. On each side of the engine, back in behind the fuel injectors, and attached to the bottom of the air plenum (what the air filter housing attaches to) there is a reed valve assembly. Each assembly actually contains 2 reed valves, one for each cylinder on that side of the engine. Each reed valve assembly has 3 connections. 2 of them connect to vacuum ports on the 2 cylinders on the side the reed valve is on. The stock hoses are red. Then there is a third connection, on the back of the reed valve assembly. This is where my problem is. It is the short piece of rubber hose that is glued to the reed valve assembly. It deteriorated and broke. I removed it from one of the reed valve assemblies, including all the glued on rubber, with a wire brush wheel on a Dremel. There is not enough of a nipple sticking out to clamp a regular hose onto.



Ok, what this little short hose does, is provide a connection point for a white plastic elbow on the right side reed valve, and a white plastic "T" fitting on the left side reed valve. A rubber hose connects to the white plastic elbow (which fits into the glued on rubber hose) on the right side of the bike, then runs around the front of the engine, where it connects to a "T" fitting on the left side. Other than the "T" fitting, the left side reed valve assembly and connections are exactly the same as the right side. The let side has a "T" fitting instead of an elbow, because TWO rubber hoses connect to it. One from the "elbow" on the right side reed valve, which connects to the left side reed valve, then another hose, which connects to the AIR valve. So, the entire reed valve system, with 2 reed valve assemblies, hoses and fittings that connect the 2 reed valves together, and 4 hoses which connect each reed valve assembly to the vacuum ports of the 2 cylinders on each side, all wind up at a single connection at the other end. The AIR valve.


Now, the AIR valve has several hoses and a wire connected to it. ONLY ONE of the hoses is a vacuum hose connected to the whole reed valve setup. Another hose connects fron the AIR valve to the air filter housing, from what I can tell, just a source of clean air. There are also 2 coolant hoses on the AIR valve, which go back to the radiator/water pump area. one is supply, one is return. I have no idea what they do. There is no temperature sensor on the AIR valve. The wire that I thought was a sensor turns out to be nothing but a heating element.


So since this entire bowl of spaghetti has no sensors of any kind, sends no signals to the ECM, just what exactly does it do, and how does it do it? What do the reed valves have to do with anything, and just what does the vacuum actually control when it finally reaches the AIR valve? And why can't I just remove all of it, plug the vacuum ports at each cylinder, and have the bike run? That would solve my whole problem, and I cannot figure out any reason why it wouldn't work.

BUT. before I took everything apart, I did just that. I removed all 4 red hoses, plugged the vacuum ports, then removed and plugged the vacuum hose at the AIR valve. The engine would start with wide open throttle, but died at about 3000 rpm, suddenly, just like you had cut the ignition off. There has got to be something to this system that I am not seeing.

Again, would appreciate any and all information about it. Jerry.
 

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I *think* I have an OEM set of manuals for my '86 SE-i somewhere. If someone doesn't beat me to it I'll try to look this thing up.
 

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The air valve is a bypass of the throttle plates that control the idle air. I really don't know what the reed valves are for other than to keep air from flowing backward through the air valve, possibly to prevent the air entering 1 cylinder from affecting the others. The wire connected to it and the coolant hoses heat the valve as the engine warms up to slow down the idle. If it is blocked off the engine will not idle. The throttle plate could be adjusted to make it idle but there would be no cold fast idle so either you would have to hold the throttle until it warmed up enough to idle or set the idle too high for when the engine is warm. The throttle position sensor would have to be adjusted also to compensate for the misadjusted throttle plates.
 

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DaveO430 wrote:
The air valve is a bypass of the throttle plates that control the idle air. I really don't know what the reed valves are for other than to keep air from flowing backward through the air valve, possibly to prevent the air entering 1 cylinder from affecting the others. The wire connected to it and the coolant hoses heat the valve as the engine warms up to slow down the idle. If it is blocked off the engine will not idle. The throttle plate could be adjusted to make it idle but there would be no cold fast idle so either you would have to hold the throttle until it warmed up enough to idle or set the idle too high for when the engine is warm. The throttle position sensor would have to be adjusted also to compensate for the misadjusted throttle plates.
Then the throttle position sensor would seem to be my biggest problem. I do not need a fast idle, as I live in AZ, where the engine is always already warmed up. I run my 2 old cars with no choke year round, they start and run fine.

But the throttle position sensor cannot be easily adjusted. I was going to remove it while I had everything apart, so I could soak the throttle bodies in a bucket of carb cleaner, but it appeared to be riveted in place. Looking in the manual, I discovered that it was installed with bolts that the heads broke off of when you reached a certain torque, that you adjusted it, then tightened the bolts until the heads broke off, so it would not move.


Which way would the throttle position sensor need to be adjusted? The original adjustment procedure I have is somewhat confusing. it says to:

1. Insert a 2.9mm guage between the throttle valve arm and stop screw. Where is that exactly?

2. Turn the sensor until output voltage is 0.475-0.479. Start engine, and recheck voltage. If it is still ok, then go ahead and tighten the screws until the heads break off. Where do you check the voltage? The throttle position sensor is a sealed unit, with 3 wires, which terminate in a white plastic connector up by the steering head. I disconnected this when I removed the throttle bodies.

I seem to be missing some information here. And would you even follow that procedure if you had changed the position of the throttle shafts? Also, do you have to use "break head" bolts, or will regular bolts work, which would make it a whole lot easier to readjust it later on if need be? I realize this information, and the "break head" bolts came from Honda, probably to prevent owners from fooling with it once set, way back when it was new. But now that it is 26 years old, and broken, I need to fool with it.
 

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You would have to have or make an adapter harness to break into the ECU harness to do the adjustment properly but it may be fine without it. Those old systems were not nearly as sensitive as the new stuff. I am thinking it may be a little too rich at idle without adjusting the sensor but the only way to know for sure is try it. Those screws can be removed by tapping them counterclockwise with a small punch or chisel or cut a slot in them with a hacksaw blade. Then replace them with regular screws.
 

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Thanks. Unfortunately it already was a bit to rich at idle, and even at full throttle. Even after it was warmed up completely, I could rev it up on the centerstand, and see black smoke. Not much, but enough to see. It was also getting poor gas mileage. But, all that was with vacuum leaks at both reed valves, in the hoses that connect the valves and the AIR valve together, not the smaller red hoses that connect the reed valves to the intake vacuum ports. It idled to fast when I bought it, and I manually lowered it with the idle screw.

I am assuming that to adjust the throttle position sensor, you turn it with the screws loose. If I mark it's position with an engraver, then remove the screws and the sensor, and put it back with the marks lining up, it will be the same?

If it is too rich, is it possible to make a minor adjustment to the sensor just by the way it is running. I'm assuming here that one way = rich and the other way = lean? Or is trying that not a good idea? Is it likely to cause damage by making minute adjustments to it?


Sorry about all these questions, I have never worked on anything like this before. And it has been sitting in my yard disassembled for almost 2 weeks now. I would like to get it running again. Jerry.
 

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jerry, can thgat air hose connection you are refering to be plastic welded? like the body shop guys do nowadays?
 

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JerryH wrote:
I am assuming that to adjust the throttle position sensor, you turn it with the screws loose. If I mark it's position with an engraver, then remove the screws and the sensor, and put it back with the marks lining up, it will be the same?
Jerry, the book tells you how to adjust it.

Loosen the screws.

Turn the key on.

Measure the voltage at the throttle switch.

Adjust to @.48 volts

Start the bike, recheck voltage at idle when warm. Should still be .48.

Tighten screws.

Any other setting is compensating for problems somewhere else. If you're lean or rich at idle, the throttle switch will keep you lean or rich through the entire sweep of the switch.

.48 volts. Period.
 

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JerryH wrote:
Thanks. Unfortunately it already was a bit to rich at idle, and even at full throttle. Even after it was warmed up completely, I could rev it up on the centerstand, and see black smoke. Not much, but enough to see. It was also getting poor gas mileage. But, all that was with vacuum leaks at both reed valves, in the hoses that connect the valves and the AIR valve together, not the smaller red hoses that connect the reed valves to the intake vacuum ports. It idled to fast when I bought it, and I manually lowered it with the idle screw.

I am assuming that to adjust the throttle position sensor, you turn it with the screws loose. If I mark it's position with an engraver, then remove the screws and the sensor, and put it back with the marks lining up, it will be the same?

If it is too rich, is it possible to make a minor adjustment to the sensor just by the way it is running. I'm assuming here that one way = rich and the other way = lean? Or is trying that not a good idea? Is it likely to cause damage by making minute adjustments to it?


Sorry about all these questions, I have never worked on anything like this before. And it has been sitting in my yard disassembled for almost 2 weeks now. I would like to get it running again. Jerry.
Yes you can turn it with the screws loose and if you remove it, it only goes back on 1 way.
It won't hurt to try to adjust it. Make sure the vacuum hoses to the PB (vacuum) sensors are good first. If they are not getting proper vacuum it will run rich. Also the TW (water temp) sensor, if it's resistance is too high it will run rich. It can be fooled by adding a resistor in parallel to lean it out or in series to richen it.

Another thought; could the hole be tapped and a hose barb installed to reconnect the air hose.
 

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All the PB hoses have been replaced, and the sensors seem to be working. No flashing lights on the ECM.

I believe the water temp sensor is ok as well, but I understand what you are saying. This stuff is sure different from the new digital stuff.

As for repairing the reed valves, I have considered about every possibility. There is not enough sticking out to clamp a hose on, I have considered cutting threads on both the outside and the inside. The outside has a slight taper to it which would interfere with cutting threads, and which causes a hose to slip right off. Putting them on the inside would reduce the diameter of the air outlet. I don't know if that would make a difference or not. The vacuum may have to be just right, like the resistance on the sensors. Partially blocking it might not work. Also where the hose was glued on is aluminum and very thin. Would be easy to crack it with a tap or die.

I also considered relocating the reed valves to some place where I can get too them without removing the entire intake system, in case a homebrew repair failed, but that would require longer hoses, in the case of the red hoses between the vacuum ports on the intake manifolds and the reed valves, they would have to be a LOT longer. Again, not sure if that would make a difference. Sure would be nice if someone out there sold rebuilt parts, like they do for cars.
 

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Jerry, Can you drill the short hose connections out and install a barb fitting on the box. I have done this on water tanks where the end of the barb fitting is 1/4 threaded fitting that I can put rubber washers on each side of the box and a nut to seal it in place, then the hose would fir right onto the barb.
 

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glhonda wrote:
JerryH wrote:
I am assuming that to adjust the throttle position sensor, you turn it with the screws loose. If I mark it's position with an engraver, then remove the screws and the sensor, and put it back with the marks lining up, it will be the same?
Jerry, the book tells you how to adjust it.

Loosen the screws.

Turn the key on.

Measure the voltage at the throttle switch.

Adjust to @.48 volts

Start the bike, recheck voltage at idle when warm. Should still be .48.

Tighten screws.

Any other setting is compensating for problems somewhere else. If you're lean or rich at idle, the throttle switch will keep you lean or rich through the entire sweep of the switch.

.48 volts. Period.
Compensating for problems somewhere else is the whole idea here. Both of the reed valves are bad, and I am trying to find a way to run it without them.
 

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jobe05 wrote:
Jerry, Can you drill the short hose connections out and install a barb fitting on the box. I have done this on water tanks where the end of the barb fitting is 1/4 threaded fitting that I can put rubber washers on each side of the box and a nut to seal it in place, then the hose would fir right onto the barb.
Possibly, but there is not much to work with. It's a very thin aluminum casting, and would be easily broken. There is no way to drill it out without cutting off the short piece that the original hose was glued onto, as it is eggshell thin. As far as what is actually inside the housing, I don't know for sure, I've had both covers off, but you really can't see that part. Drilling could ruin the whole valve. Putting something inside the existing opening to attach a hose to would reduce the size of the opening, which might or might not make a difference in how it worked. Ideally, it needs a hose attached to the outside of it, the way it was designed in the first place. I don't have any way to attach a hose to it like they did at the factory, but I have found that a short piece of 1/2" copper pipe fits over it just slightly loose. I am considering trying to epoxy a piece of pipe over the outside of the fitting, then attach the hose to the pipe. It would have to be done without getting any epoxy down into the valve.


I now have 4 valves with the same problem, the 2 that came off the bike, and 2 more I ordered to replace them with, which turned out to have the same problem, hoses rotted and split. So I guess I can use a couple of them to experiment with. If I break one, at least I'll know for sure what is inside.

Before they were discontinued, these things sold for about $50 apiece, for a little over $100, I could have had a whole new system, hoses and all.
 

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JerryH wrote:

Compensating for problems somewhere else is the whole idea here. Both of the reed valves are bad, and I am trying to find a way to run it without them.


My mistake. When you asked for fuel injection help, I thought you were trying to repair the bike.
 

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glhonda wrote:
JerryH wrote:

Compensating for problems somewhere else is the whole idea here. Both of the reed valves are bad, and I am trying to find a way to run it without them.


My mistake. When you asked for fuel injection help, I thought you were trying to repair the bike.
Actually I am trying to make the bike run. I would love to repair it, properly. But the parts are no longer available, so something will have to be improvised.
 

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Well after taking the afternoon off, and searching through 4 different hardware/home improvement stores, with one of the reed valves in hand, I believe I finally came up with something that will work. I found some short (2") brass pipes about 1/4" in diameter, with tapered threads on each end. The threads fit tight into the opening in the valve where the hose was glued to, I put a nut on the threads on the other end so I could turn the pipe without crushing it. I kept screwing it in and out until it cut threads all the way to the end of the threads on the pipe, took the pipe out, put red locktite on them, and screwed it back in, then cut it off with a tubing cutter. Tomorrow I will reinforce it with epoxy on the outside. Then I will use a combination of 1/4" fuel line, and 1/4" plastic elbows to connect everything back together. It should be stronger than the original, it is not only threaded in, but glued in with red locktite on the inside, and epoxy on the outside.
 

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Ok, I've finally got both valves repaired, all new hoses and connectors, got everything cleaned, and am ready to put it back together and hope it works. Unfortunately, I managed to lose one part. The little clip that holds the reed valve body in place on the right side. I'm sure I can probably rig something, but after going this far, I would like to put it back right. If anybody happens to have one, let me know. I will also try Whiteys. It's part #16119-MG9-951 on cheapcycleparts.com.
 
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