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freebo86

Principles and Operation of “Enrichment Valve”

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Posted (edited)

So, as some of you may know me from the “adjusted valves, now machine is a time bomb” thread, I’m back with some questions. 
 

So as I’ve resolved my other issue(s) and didn’t want to clutter the old thread I decided to start this one. I was out last evening messing around with the choke to find the “sweet spot”. Here is my issue/dilemma.

 

If I mess around with the choke enough where the bike warms up a bit I can get it to a point I can’t start it again. Only way to start the bike, is completely pulling the enrichment valve out of the carb. Hit the start button, bike cranks and turns on - obviously running bad as now there is no enrichment valve anymore installed.
 

If I do a full cold start, with enrichment valve installed If feather the throttle, once I get it warm it idles good. 


 

I am trying to understand what on the enrichment valve could be causing this issue with starting issue bud it’s obviously not as bad as previously. Am I getting lack of air? Because it appears to me if I pull the entire enrichment valve out, I get more air in the carb and bike starts? Am I understanding this correctly? So why wouldn’t it have the same effect if I pulled the choke knob out?

Edited by freebo86

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I you use the correct name of the part and it might help you to understand how it works  better , everyone calls it a choke , but it's real name is a " fuel enrichment valve " , air is just the form of transportation for the fuel 

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14 minutes ago, Fishfiles said:

I you use the correct name of the part and it might help you to understand how it works  better , everyone calls it a choke , but it's real name is a " fuel enrichment valve " , air is just the form of transportation for the fuel 


There fixed terminology. 

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Something else I noticed, I am running spark plug DPR6EA-9 which is rated for cold climates. 
 

The standard plug is rated for DPR7EA-9. 
 

Don’t think this will make a difference but should  I maybe switch plugs anyways and go with the standard?

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I would think your problem could be in the bore of the  carb where the enrichment plunger slides , maybe it is scared and not sealing , or maybe the port that supplies fuel pass the plunger is partially plugged up , or maybe the cable is stretched ----- I have not paid attention to the cable on my 450S , but my 300s have a clip where the cable goes into the housing of the "choke " lever , there are like 4 slots in the cables' end piece  , so the cable has an adjustment , not sure how your 450 with a pull know is set up 

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Oh yea , I would try changing the plug , can't hurt 

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I would change the plug—how’s that plug look anyway? Dark, sooty?

 

If so, try leaning it out a bit 

 

If you consider the piping route of the enrichment system you’ll see a hole in the carburetor throat Intake and outlet sides. Those are connected by upstream (intake) and downstream (outlet) passages that lead to the enrichment bore. A third passage branches off the downstream side but I can’t remember but i think it goes to the bowl—it has to.

 

Imagine your carb setup. carb chokes block airflow, enriching the AF mix. on this carb the only thing that changes when “choked” you’re opening a valve. 
 

good question what does it do? you open the valve while starting—the vacuum created by the retreating piston sucks a little extra fuel from the enrichment passage. If the passage is overly dirty then enrichment is starved. If the valve is hanging up, then the enrichment circuit stays open to a small degree. 


That’s why I suggested leaning your mix a bit. @bcsmansuggested not opening the throttle on warm startup. Another thing to try—after it’s good and warm, pull the air filter off and see how it starts.

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Which is why I'm a fuel injection fan 😆

 

Like fish says, make sure the orifice the plunger rides in is smooth and clean. Especially where the need goes in. The plunger too. I used to coat them with a little moly grease on my old Kingquads. I've found them stuck and corroded. Does the spring seat it completely?

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Yes as @Tim-ANC mentioned in the above post I forgot to ask if you put a little grease on the plunger before installing the new one.  I believe it is mentioned in the service manual or here somewhere but needs to be done....

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Thanks. The plug is wet and dark when I try to start it and it won’t actually start. So it’s getting fuel. 
 

So if the enrichment valve isn’t sealing good against the carb bore you would think it would still start? Because when I remove the enrichment valve completely it runs and I feel the air sucking in the carb bore where it was. So with the enrichment removed it’s getting extra air, no?

 

I will try and lean out the mixture and grab the other type of sparkplug 

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Seem to remember the plunger is what got you running a while back , might not be 100% right just yet ---- what carb do you have on the atv ?  the one that came with it ? Did we ever check the code to see if it is the correct carb ? --- what about the cable being messed up and holding it back a bit ? Is the cable smooth or sticky 

 

I had to bite the bullet and buy a carb new OEM for my 450 in the past , never could get it right 

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Posted (edited)
1 hour ago, Fishfiles said:

Seem to remember the plunger is what got you running a while back , might not be 100% right just yet ---- what carb do you have on the atv ?  the one that came with it ? Did we ever check the code to see if it is the correct carb ? --- what about the cable being messed up and holding it back a bit ? Is the cable smooth or sticky 

 

I had to bite the bullet and buy a carb new OEM for my 450 in the past , never could get it right 


OEM carb, checked the number on it that it’s in fact the OEM one. @retro confirmed this a while back with me. Carb has been cleaned and rebuild (shindy kit). Plunger is OEM Honda from the dealer. 
 

Cable is smooth moving. I checked it as well. 
 

unless something with the enrichment passages is still a bit buggered/blocked?

Edited by freebo86

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Very possible you’re simply running rich. How many turns out are you on the pilot screw? Quite possibly a sticky cable OR if cable was replaced—it’s too short. 
 

im pretty sure way back you proved this was the OEM carb.  

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1 minute ago, Goober said:

Very possible you’re simply running rich. How many turns out are you on the pilot screw? Quite possibly a sticky cable OR if cable was replaced—it’s too short. 
 

im pretty sure way back you proved this was the OEM carb.  


Yes, oem carb. 
 

2.5 turns out. Cable is smooth moving. Already checked this out. 

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IDK spec on these—I’d lean it by 1/2 turn and readjust the idle. 
 

what altitude are you? Does the service manual state a high altitude adjustment for the model?

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So freebo I did an experiment with my 450 this morning.  I wanted to see what happens when I have ridden the 450 until warmed up then shut off for a few minutes, and turn back on.  I tried while still warm with the choke button pulled out and it didn't want to start very well as I would expect, too much fuel.  So we had talked the other night in chat about this and I wanted to how mine worked.  So when warm I can't use the choke to restart, it did but sounded like it was gonna stall.  I think you said you also use no choke when trying to start warm so according to my experiment it's the way you should be doing it.  And unfortunately for you it sounds like it still gets too much fuel.....

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By chance did the seat for the throttle valve (main jet holder holds it in place) fall out while working on the carb? That would give it unrestricted fuel spray and when you remove the EV it's possible it lets in the little extra amount of air to help make the flooded motor start. All the enrichment valve does is open another passage to let extra fuel/air mixture in to aid in cold starts (unlike a choke that blocks air causing a richer condition).

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Is the idle quality responsive to pilot screw adjustments? Try adjusting the pilot screw per the manual and let us know how that procedure goes. The final pilot screw setting should be 1/2 turn out from decaying idle. If adjusting the pilot screw doesn't seem to make the idle quality respond like the manual outlines, then there is probably a rich condition in another circuit to diagnose.

 

 

pilot-screw.png

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On 4/6/2021 at 12:39 PM, retro said:

Is the idle quality responsive to pilot screw adjustments? Try adjusting the pilot screw per the manual and let us know how that procedure goes. The final pilot screw setting should be 1/2 turn out from decaying idle. If adjusting the pilot screw doesn't seem to make the idle quality respond like the manual outlines, then there is probably a rich condition in another circuit to diagnose.

 

 

pilot-screw.png

 

Playing with the pilot screw does alter the idle. But it almost seems like it’s at the extreme on both ends. Like wide open (almost fully out) or almost fully in.. 
 

 

On 4/6/2021 at 11:57 AM, toodeep said:

By chance did the seat for the throttle valve (main jet holder holds it in place) fall out while working on the carb? That would give it unrestricted fuel spray and when you remove the EV it's possible it lets in the little extra amount of air to help make the flooded motor start. All the enrichment valve does is open another passage to let extra fuel/air mixture in to aid in cold starts (unlike a choke that blocks air causing a richer condition).


Which holder are you referring to? The white plastic little piece that sort of just sits around the main jet? 

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4 minutes ago, freebo86 said:

Which holder are you referring to?

 

He is referring to the needle jet holder. It emulsifies fuel after fuel passes through the main jet. :

 

needle-jet-holder.png

 

8 minutes ago, freebo86 said:

Playing with the pilot screw does alter the idle. But it almost seems like it’s at the extreme on both ends. Like wide open (almost fully out) or almost fully in.. 

 

Good clue... try bypassing the air cutoff valve vacuum supply by disconnecting the vacuum hose from the carb and plug that vacuum port. Then turn the pilot screw in & out again to see if the idle quality becomes more responsive.

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Posted (edited)
1 minute ago, retro said:

 

He is referring to the needle jet holder. It emulsifies fuel after fuel passes through the main jet. :

 

needle-jet-holder.png

 

 

Good clue... try bypassing the air cutoff valve vacuum supply by disconnecting the vacuum hose from the carb and plug that vacuum port. Then turn the pilot screw in & out again to see if the idle quality becomes more responsive.


the holder is there. From memory it threads in so not sure how it could fall out?


Does it matter which vacuum line I pull out to plug? It connects on either side of the carb. 

Edited by freebo86

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There is only one vacuum hose that connects to the air cutoff valve. Disconnect that hose and plug it temporarily. You are testing whether the air cutoff valve diaphragm has a hole it it (allowing vacuum to leak), or not.

 

air-cutoff-valve.png

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The other small hoses that connect to the body of the carb are vent & drain hoses. Make sure that you have them all connected right.

 

carb.png

 

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27 minutes ago, retro said:

There is only one vacuum hose that connects to the air cutoff valve. Disconnect that hose and plug it temporarily. You are testing whether the air cutoff valve diaphragm has a hole it it (allowing vacuum to leak), or not.

 

air-cutoff-valve.png


There is two places that a hose connects to on that air cut off valve... both locations goes to opposite side of the carb. 
 

which one are you referring to?


2849C75A-8D74-4781-BDD5-BFC48AC74DE2.jpeg

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7 hours ago, freebo86 said:


the holder is there. From memory it threads in so not sure how it could fall out?


Does it matter which vacuum line I pull out to plug? It connects on either side of the carb. 

 

It would be the needle jet in the picture provided, you can look through the bore of the carb and see it sticking up just a little.

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