Scooter surges when choke is turned off, then dies

[sgurtman]

Hey guys,

So I bought an old Honda NF75 off trademe. Since buying it I've taken apart and cleaned out the carb. Nonetheless, I'm still having issues with it. It starts fine when using choke. However as soon as I turn the choke off or throttle up it surges a bit, and then dies. What do you all think is worth examining. I think the seals are fine (as mo change when spraying with carb cleaner). I'm at a bit of a loss as carb was real clean when I took it apart even before cleaning. Anything you could suggest may be the culprit? I defer to your collective wisdom.

Cheers!

[Akzle]

do you let it warm up? Is it running rich? What does the plug taste like?

[fridayflash]

did you manage to clean out all jets and passages with a fine bit of wire (pull a bit out of a wire brush) or compressed air etc?
sounds like idle jet/passage is blocked..itd be interesting to see what happens if you hold the revs up and then shut of the choke
...main jet may be clear, pilot jets are very fine so pay attn to that also

[sgurtman]

do you let it warm up? Is it running rich? What does the plug taste like?

Do you mean spark plug? I honestly never thought to taste it although I just changed it out today thinking it may be the culprit. I think I'll let it warm up for 30 minutes tomorrow and see what happens when I push in the choke. I'm pretty sure the pilot is clean as I sprayed carb cleaner directly into into and saw spray coming out. I'll let you know the results of the extended warm up and also the results of the throttle up test that was suggested.

[unstuck]

Do you mean spark plug? I honestly never thought to taste it .

Oh please please please, let us know what it tastes like.:killingme:killingme

[Akzle]

Do you mean spark plug? I honestly never thought to taste it although I just changed it out today thinking it may be the culprit. I think I'll let it warm up for 30 minutes tomorrow and see what happens when I push in the choke. I'm pretty sure the pilot is clean as I sprayed carb cleaner directly into into and saw spray coming out. I'll let you know the results of the extended warm up and also the results of the throttle up test that was suggested.

err. Running choked for half an hour will probably foul/flood/kill it.
Check the air pilot screw is set to spec, and that the butterfly plate isnt blocking the idle passage when closed.

[Akzle]

and of course i meant spark plug, licking a sump plug would just be silly.

[sgurtman]

err. Running choked for half an hour will probably foul/flood/kill it.
Check the air pilot screw is set to spec, and that the butterfly plate isnt blocking the idle passage when closed.

So I found that it runs fine with choke in when at throttle. So I'm thinking it may be idle jet is still blocked. Air pilot screw is on outside of carb, right? It's the other screw that's not the idle speed?

[Akzle]

So I found that it runs fine with choke in when at throttle. So I'm thinking it may be idle jet is still blocked. Air pilot screw is on outside of carb, right? It's the other screw that's not the idle speed?

correct. but have you checked the plug?
there are at least several screws on your carb. some hold it together. one adjusts the idle, one, if you pulled it out, has a pointy end. that's your air pilot. wind it in (gently) until it's seated. then pick a number between 1 and 5, and unwind it that many turns. if it doesn't go good, try again with another number.

[sgurtman]

correct. but have you checked the plug?
there are at least several screws on your carb. some hold it together. one adjusts the idle, one, if you pulled it out, has a pointy end. that's your air pilot. wind it in (gently) until it's seated. then pick a number between 1 and 5, and unwind it that many turns. if it doesn't go good, try again with another number.

Weirdly that has absolutely no effect. I took apart the carb again and it seems that the idle mixture screw has no effect because the choke plate is not fully closing even with the choke completely off. Heres a video I took: http://youtu.be/O3cyqePWnsU
I'm guessing this is not normal and maybe the choke plate is too big?

Also, can you point out to me which is the idle jet in this picture:

286006

[Akzle]

Weirdly that has absolutely no effect. I took apart the carb again and it seems that the idle mixture screw has no effect because the choke plate is not fully closing even with the choke completely off. Heres a video I took: http://youtu.be/O3cyqePWnsU
I'm guessing this is not normal and maybe the choke plate is too big?

Also, can you point out to me which is the idle jet in this picture:

286006

the choke PLATE?
On a scooter?
Methink youll find its a little black bitch unit held on by 1 or 2 screws, plugs in top of carb.
Im talking about the AIR pilot, idle circuit.
Im guessing theres a stem that pokes in that bottom hole, rather than a jet, per sé.
Rotate that carb so youre looking in engine side, youll see the butterfly plate and the air pilot hole, on the top of the barrel. The plate should, for starters, cover about 1/2 the hole. Your idle adjust screw, will get you there.

Edit. Unless your idle is a tapered screw that lifts the slide. Then your main is your idle, and theres no butterfly...

[Akzle]

post pics from every angle.

[unstuck]

Mixture screw is the one below and to the left of the idle adjustment screw in this pic.


286012

[Akzle]

Mixture screw is the one below and to the left of the idle adjustment screw in this pic.


286012

holy fucking what. that'd be the air pilot?

so the choke IS a plate? and actuates on that black shit?

and there's no slide?


i'm going to go rock myself and hum in the corner.

[sgurtman]

the choke PLATE?
On a scooter?
Methink youll find its a little black bitch unit held on by 1 or 2 screws, plugs in top of carb.
Im talking about the AIR pilot, idle circuit.
Im guessing theres a stem that pokes in that bottom hole, rather than a jet, per sé.
Rotate that carb so youre looking in engine side, youll see the butterfly plate and the air pilot hole, on the top of the barrel. The plate should, for starters, cover about 1/2 the hole. Your idle adjust screw, will get you there.

Edit. Unless your idle is a tapered screw that lifts the slide. Then your main is your idle, and theres no butterfly...

Picture from all around. The float bit is taken off already.

286018286019286020286021286022

[unstuck]

Mixture screw is the one above your thumb in pic 5.:niceone:

[sgurtman]

ok, I just took a look at the carb and it appears I have no idle jet!!! If you look at the first pic I posted you'll see (I think but I'm a noob so maybe not) the normal jet which I have, and then an empty place where there should (I guess?) be a pilot jet.

Is a pilot jet absolutely necessary or is it normal to not have one?

[Akzle]

Aha, I found the pilot air screw on the bottom of the float bit of the carb. Now the issue is, whenever I open it a bit it leaks fuel.

float valve fuckeroo.
Or. Its not the air pilot.

[sgurtman]

float valve fuckeroo.
Or. Its not the air pilot.

Yea, just realized that it wasn't the air pilot. Derp derp... :brick:

But what does this go to? Sorry, I'm just learning as I go.
286025

[unstuck]

Is it a GCV 160 or something else? Whats written on it?

[Akzle]

Yea, just realized that it wasn't the air pilot. Derp derp... :brick:

But what does this go to? Sorry, I'm just learning as I go.
286025

thats where i thought youd hav a stem to suck fuel up. Or a bowl vent.
Im feeling like a girl on this one.

Ill be in akl early next week. Where are you?

[Akzle]

ok, I just took a look at the carb and it appears I have no idle jet!!! If you look at the first pic I posted you'll see (I think but I'm a noob so maybe not) the normal jet which I have, and then an empty place where there should (I guess?) be a pilot jet.

Is a pilot jet absolutely necessary or is it normal to not have one?

no. This carb sets idle as a throttle stop. Your main is your idle. The needle never *fully* seats.

[sgurtman]

thats where i thought youd hav a stem to suck fuel up. Or a bowl vent.
Im feeling like a girl on this one.

Ill be in akl early next week. Where are you?

So I sprayed some carby cleaner in the hole and it dripped out here, not sure how cause it looks completely sealed:

286036286036

[sgurtman]

Is it a GCV 160 or something else? Whats written on it?

its a Kei Hin BB Serial: 24AWOA

[sgurtman]

FML, I got it working but then decided to mess with it to get the idle slower. Now I can't get it to work without surging. Even when I turn out the mixer screw over 12 turns it still won't idle. Is it possible to change the screw to make it so I have to turn it less to get the same air intake?

[GSeX]

Have you disassembled the carb and cleaned thoroughly every channel inside it and the jets? sometimes you have to clean it completely a few times, and use a thin wire to poke any crud out of the tiny gaps. then as long as there's no air leaks and it's getting fuel, it should idle with the screw at around 2 and a half turns