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Discussion Starter · #1 ·
I have an 87 Foreman that I purchased new. I am in the processing of “Refreshing” this thing. Muffler, fuel tank and brakes done. It has always run a tad rich on acceleration. In the past, this was not a real concern. Now that I am retired, I am investigating this rich thing a little further. I have had some carb issues before. This was due to the main air bleed getting clogged. Of course, this resulted in overall rich condition.

I just finished a carb cleaning and all is well, except for the rich on acceleration thing. There is not a wealth of information on these Keihin/Honda QA carbs. The slide seems to be timed correctly and the needle is in the middle, third, notch. Jets are the correct size. Enrichment, choke, valve is seating properly. I “Think” all of the air bleeds and fuel passages are clean.

Any thoughts?

Thanks in advance,
Bill
 

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sounds like your pilot jet is not clean, and adjusted right ?. take care to notice every part in the hole !!. there is in order, tiny o-ring, tiny washer, spring, and screw needle. if you missed,lost, double stacked the o-ring ?, it won't run right. I would start with a carb rebuild kit, shindy is what I use the most. there is a great sticky by me, in the repair section on how to clean a carb, please read it :).
 

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Have you thought of dropping the needle one notch (raise the clip) to make it leaner
I did that to mine and fixed the rich running problem
gonna toss in my .02's worth on this clip thing. does any one even know why they put the clips there ?, when to move them ?. wellllllll..gonna give you the low down. there is two main reasons they put the grooves there ?, one: is when the soft brass main jet needle seat wears ?, when it does this ?, you make up for the wear by dropping the clip, then it drops the main jet needle. the other main thing, two: is when your at a certain sea level ?, this allows you to compassionate for the air density when at a high altitude. soooooo...changing the clip on the main needle IS NOT THE CORRECT WAY TO FIX A RICH MIXTURE !. :).
 

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Discussion Starter · #7 ·
Where does the bleed air, for the main jet come from? Does it come past the needle from the carb bore? Is the air supposed to come past that needle bushing from the air bleed passage? When checking, very little air comes through the air bleed passage, by that needle guide bushing.

I "Assume" that air is supposed to come, through the air bleed, past the brass bushing/Jet holder seat and through the jet holder emulsifier holes. If this is the case, it ain't happening. Well, IMHO: it ain't happening enough.
 

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Where does the bleed air, for the main jet come from? Does it come past the needle from the carb bore? Is the air supposed to come past that needle bushing from the air bleed passage? When checking, very little air comes through the air bleed passage, by that needle guide bushing.

I "Assume" that air is supposed to come, through the air bleed, past the brass bushing/Jet holder seat and through the jet holder emulsifier holes. If this is the case, it ain't happening. Well, IMHO: it ain't happening enough.
kinda lost here ?, where are you getting this bleed air info from ?. I've never heard of any '' bleed '' air in all my years ?. as far as I know, all air is drawn through the body of the carb, there is passages in the carbs body where air is mixed in with the fuel mixture that is drawn up from the float bowl, where your idle jet, main jet is held. this is done though suction from the motor. as the fuel is drawn up, and into the intake, the fuel mixture, or in this case, the pilot jet needle which is in the front lower outside bottom of the carb, mixes the correct amount of fuel and air before it enters the intake side of the cylinder. I have no idea what your calling '' bleed '' air ??. you lost me on this :).
 

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Changing a needle clip height, I'm told, gives you about half of one number on the main jet. As Shade says, it's for very minor adjustments. Fine tuning.

Rick

Sent from my SAMSUNG-SM-N900A using Tapatalk
 
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Changing a needle clip height, I'm told, gives you about half of one number on the main jet. As Shade says, it's for very minor adjustments. Fine tuning.

Rick

Sent from my SAMSUNG-SM-N900A using Tapatalk
yep, it's not meant for changing the fuel mixture ?, it's for main jet seat wear ?, or changes in elevation , that's it !. the pilot jet needle ( fuel/air mixture ) is for fixing the rich or lean mixture..not the clip groove.
 

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You never asked where the OP is from. If he is in Colorado or the likes, dropping the needle will help.

Coming from duel sport bikes, we often change the needle or add/subtract a washer from under the needle. As he said, it has always ran a bit rich.
 

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Changing a needle clip height, I'm told, gives you about half of one number on the main jet. As Shade says, it's for very minor adjustments. Fine tuning.

Rick

Sent from my SAMSUNG-SM-N900A using Tapatalk
yep, it's not meant for changing the fuel mixture ?, it's for main jet seat wear ?, or changes in elevation , that's it !. the pilot jet needle ( fuel/air mixture ) is for fixing the rich or lean mixture..not the clip groove.
Jet seat wear is why i had to drop mine, my old boss, advised me the exact samething as shade and rick pointed out.
 

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Discussion Starter · #13 · (Edited)
I found this pic on the net. I know it is not the same carb, but is a good example of an air bleed.

Gun


Air bleeds are a necessity with carb engines. The bleed allows a small amount of air to be mixed (emulsified) with the fuel before entering the carb bore. If not for air bleeds, straight fuel would be sucked into the carb bore. Some carb engines have altitude control systems. These systems control the amount of air going through the bleed, more air for high altitudes, less for low altitudes.

If I block the needle hole, in the throttle bore, and blow air through the hole for the jet tube, very little, if any, air comes through the bleed hole. I am suspecting the needle bushing (seat for jet tube) is blocking the air bleed.

I am going to knock that seat out and check.
 

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I found this pic on the net. I know it is not the same carb, but is a good example of an air bleed.

View attachment 64401

Air bleeds are a necessity with carb engines. The bleed allows a small amount of air to be mixed (emulsified) with the fuel before entering the carb bore. If not for air bleeds, straight fuel would be sucked into the carb bore. Some carb engines have altitude control systems. These systems control the amount of air going through the bleed, more air for high altitudes, less for low altitudes.

If I block the needle hole, in the throttle bore, and blow air through the hole for the jet tube, very little, if any, air comes through the bleed hole. I am suspecting the needle bushing (seat for jet tube) is blocking the air bleed.

I am going to knock that seat out and check.
whoaaaa bro !. that air bleed you see is a jet !!..its the small jet inside the float bowl, unless it's clogged ? ( and I've never seen that jet stopped up ), it has nothing to do with why your motor/carb is running rich !!. this is a pilot jet needle issue, as I pointed out back a few post in this thread :).
 

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Discussion Starter · #15 ·
It took some more investigating, but I found the problem, a partially blocked air bleed orifice. This orifice is on the branch of the passage that is the air bleed for the main jet. With the slide cover removed, it is in the hole down in the left rear of the slide compartment. The tiny brass orifice is barely visible through this hole. I used some .010 spring wire to prod around and find the center of the orifice. A little wrestling with the wire and it went through. After moving up to a .020 wire, I pushed on it fairly hard and something broke loose. I blew through the hole and some tiny, what appeared to be, aluminum shavings came out of the main jet tube hole. A .028 wire is all that will go through the orifice, about .7mm.

I reassembled and reinstalled the carb. The thing runs great, not the least bit rich. I probed the exhaust and the A/F ratio is around 13:1 on acceleration. I have to guess that the aluminum shavings have been in there since it was new, probably from drilling the passage.

Next project, figuring why it is hard to shift.
 

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It took some more investigating, but I found the problem, a partially blocked air bleed orifice. This orifice is on the branch of the passage that is the air bleed for the main jet. With the slide cover removed, it is in the hole down in the left rear of the slide compartment. The tiny brass orifice is barely visible through this hole. I used some .010 spring wire to prod around and find the center of the orifice. A little wrestling with the wire and it went through. After moving up to a .020 wire, I pushed on it fairly hard and something broke loose. I blew through the hole and some tiny, what appeared to be, aluminum shavings came out of the main jet tube hole. A .028 wire is all that will go through the orifice, about .7mm.

I reassembled and reinstalled the carb. The thing runs great, not the least bit rich. I probed the exhaust and the A/F ratio is around 13:1 on acceleration. I have to guess that the aluminum shavings have been in there since it was new, probably from drilling the passage.

Next project, figuring why it is hard to shift.
glad ya got it running great !. as for the shifting ?, start with checking/adjusting your clutch.
 
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