Fuel from needle jet at idle? WTH????

Alright, I'm baffled.

This is on a Venture with a Vmax Engine in it (at least from the cylinder block up it is).

It's running pig rich at idle and low rpms. Will run a couple days and then cabon fouls the plugs.

I tried to adjust the idle fuel screws and discovered that they had no effect if they were fully seated in or almost hanging out of their bores.

I popped open the airbox and stuck an eye ball on the slides, looking for anything abnormal.

Then I saw a stream of fuel coming out around the needle and sliding along it in each carb. Throttle blip would make even more fuel come out as the slides responded normally to a throttle blip. It actually looked like and accelerator pump shot on a holley carb coming out of each needle port!

WTF? I've never seen (or maybe noticed) that before.

I figured that the fuel level was probably stupid high and allowing vacuum to force it out around the needle, but just not high enough to overflow on to the ground. Nope. Using the clear tubing method, it measures to about 18mm.

Throttle blades are shut, I had it adjusted down to 500 ish rpm with the idle stop before it would become so unstable it would just die. Quick look a the blades and they sure looked as closed as they get.

These are the venture carbs, currently with 140 jets (genuine mikuni jets). The 140 is an initial stab a main jet size, but I can't even got to run a plug chop until I figure out what's going on here.

So I'm baffled. Something is not right here and I just can't figure it out. I'm not a novice at carbs either, but I've never dealt with this before.

Pretty sure I should NOT be getting fuel from the needles at idle, unless the VMax does something different than pretty much every other set of carbs I've laid hands on...

Maybe I just "can't see the forest through the trees" and that's why I'm throwing the question out here.

I'm currently in the process of pulling the carbs off the bike for a complete tear down, inspection of everything right from dry float levels and up and another dip in the ultrasonic cleaner (doubtful it's plugged ports as all 4 carbs are doing the same thing).

The idle circuits are clear, I sprayed a little cleaner in the idle screw bores and it come out at the right port.

Any ideas?

Could I have missed a plugged circuit somewhere effecting the slides at idle and lifting the needles up out of the tubes enough to pull fuel? But all four doing the same thing seems to make that unlikely...

Should I be looking at PAJ1 or 2 with the change from Venture heads/cams to Vmax heads/cams?

Thing is, I know at least one guy that has run the 34 mm venture carbs on a vmax'd 1300 and they worked normally (other than re-jetting).


I'm stumped here.....
:ummm:

Stuck float- tap the bowl with the wooden end of a hammer.

blaxmax said:

Stuck float- tap the bowl with the wooden end of a hammer.

Click to expand...

that seemed logical to me too. but nope.

float levels good. checked several times. no overflowing.

not to mention, it would have to be all four carbs at once. problem is elsewhere.

have carbs apart right now, everything moving freely and flot needles clean as the day they were made.....using a 10x lighted magnifier to look at them.

Are the needle jets fully seated? Oring in its proper place?

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^ http://www.boats.net/parts/search/Yamaha/Motorcycle/1996/V-MAX 1200 - VMX12H/CARBURETOR/parts.html

What condition are the jet block plugs in?

Probably just like everyone else here-Stiff an Old.:rofl_200:
Sorry, could help it on that one.

maleko89 said:

Are the needle jets fully seated? Oring in its proper place?

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Click to expand...

Yep and yep.

dannymax said:

What condition are the jet block plugs in?

Click to expand...

yep.

so, everything looks good inside carbs.

pulled the idle screws out and all is clean and tips are intact. port is clear.

took a can of carb cleaner and sprayed through all the passages and jets. everything is clear.

at this point, im going to confirm the dry float levels and put it back together. no point in doing ultrasonic again.

i swear its like theres too much vacuum signal or something. how the heck else can it be pulling fuel around the needles unless its too high a float level.

its got to be something simple staring me right in the face and i just cant see it....

Worn needles and or needle jets. If vacuum problem could be slide hole, vac port, float bowl vents

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great white said:

so, everything looks good inside carbs.

pulled the idle screws out and all is clean and tips are intact. port is clear.

took a can of carb cleaner and sprayed through all the passages and jets. everything is clear.

at this point, im going to confirm the dry float levels and put it back together. no point in doing ultrasonic again.

i swear its like theres too much vacuum signal or something. how the heck else can it be pulling fuel around the needles unless its too high a float level.

its got to be something simple staring me right in the face and i just cant see it....

Click to expand...

Cracked intakes?

blaxmax said:

Cracked intakes?

Click to expand...

Yep, check boots; all 12 of them. Check the sync port caps. Perhaps, take a sync reading and see what the vacuum reads?

Mark

maleko89 said:

Yep, check boots; all 12 of them. Check the sync port caps. Perhaps, take a sync reading and see what the vacuum reads?

Mark

Click to expand...

I'm not following where you guys are going with a vacuum leak causing a rich condition.

Vacuum leak is a lean condition, not rich.

Would also lead to less vacuum signal over the ports, not more...

great white said:

I'm not following where you guys are going with a vacuum leak causing a rich condition.

Vacuum leak is a lean condition, not rich.

Would also lead to less vacuum signal over the ports, not more...

Click to expand...

^"i swear its like theres too much vacuum signal or something. how the heck else can it be pulling fuel around the needles unless its too high a float level."

18mm would be high

I think I might have gotten a good lead on wher ethe problem is and it makes sense with the way the bike is behaving.

I went to my service manual to look up the dry float setting and nada. Only gives the wet measurement. As I have to take half the bike apart to get the carbs out, i need a bench measurement method. Pulling the carbs on this Venture/Vmax is a major PITA because it has lots of interconnected plastic fairing bits and not as much upper frame tube clearance as the vmax frame, have to drop the front engine mounts for clearance.

So off to the stickies in the carb section and I find a dry bench measurement. It's late here and past bedtime, but I just had to know. Up out of bed and out to the garage and have a looky see at where it falls.

The quick and dirty measurement I used was 16mm from the bottom of the jet block to the bottom of the float at rest on the needle. This is supposed to be equal to 17mm on the wet measurement.

The measurement I got came out to 19mm, not 16mm. That would be 3mm too high a float level! If this is right, it could sure explain why I was getting fuel out of the needles and yet not out the overflows.

I have no idea what happened between removing the carbs from the venture 1200 and installing them on teh VMax 1200 that would change their levels or why the wet measurement would heck out at 18mm and the dry be so far out.

Regardless, this is the first time something logical for it's symptoms has popped up. Off to bed for tonight. Back at it first thing in the morning but possibility of fixing the issue is looking up!

blaxmax said:

^"i swear its like theres too much vacuum signal or something. how the heck else can it be pulling fuel around the needles unless its too high a float level."

18mm would be high

Click to expand...

18mm was below the reference line on the carb body. My venture 1200 service manual lists 14mm +- .5 mm. 1300 service manual says 15.5-16.5 mm. Vmax service manual says 16mm +- 1 mm. Forum stickies seem to indicate 17 mm as a preferred setting. 18mm should make it way lean, which is the opposite of what I'm running in to here.

see my post above for more info. My floats may be way off to the rich side. No idea why the wet measurement came out to 18mm is the floats are set too high.

All I can figure is the tabs got "bumped" of something on the last main jet change.

I'll be checking them wet on the bench this time. in and out of the bike just to check float levels is way too much work when there's a simpler faster way (IE: level on the work bench and fill them) to do it.

It can get confusing measuring the float position upside down and wet level checking them right side up......

I set floats with a gauge, and used to use a fuel bottle suspended over the carbs (on the bench) to approximate fuel pump pressure for wet level check.

Now I set with the same gauge and a longer line from the fuel pump with carbs leveled on top of test engine stand.

dannymax said:

It can get confusing measuring the float position upside down and wet level checking them right side up......

I set floats with a gauge, and used to use a fuel bottle suspended over the carbs (on the bench) to approximate fuel pump pressure for wet level check.

Now I set with the same gauge and a longer line from the fuel pump with carbs leveled on top of test engine stand.

Click to expand...

Dan-o, does that engine start?

I still use my Motion Pro aux. fuel tank to check wet levels prior to putting them back on my bike. I also use a small level to make sure the carb brackets are all tight and were installed correctly.

I still turn the carbs upside down for dry levels and use a digital caliper to set at 1.125 inches. I found that the 1/2 moon on the jet block varies in position on some blocks.

Mark-o

Danny is the fan just for light cruise speed or you got a 220 v hooked up to get the bike simulating v boost speeds hahah