NEED MAJOR HELP, fuel spitting derbi

[coggie]

hi guys,
i really need some help.

I've been building my derbi gpr 50cc (72cc) from ground up.
new crank shaft n seal, airsal tuned 72cc top end.
Metra kit exhaust, tnt 21mm carb. k and n.

I'm now having a bit of trouble,
the bike had been sat in the garage a week and fuel is ending up sitting in the exhaust (stupidly left fuel on). i emptied it and
the bike start up after a few seconds on the starter motor.
but as soon as its running its spitting fuel out the exhaust,
a fine mist at idle but when you rev it ( not gone over 6K) it seems to spit splashes of fuel out the exhaust.

id really appreciate so help if any one has ideas,

thanks very much guys.
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2005 Derbi Gpr Replica, Airsal 70cc kit, K&N, Doppler Racing Crank, Metrakit Pro Carbon Exhaust, Metrakit Carbon Reeds - Currently Being Build (Project)
(SOLD) 2005 Derbi Senda SM Limited Edition 656/999 (SOLD)

[mickfulton]

Had a similar prob with a gpz. Heard a stuck float can cause the varbs to get too much fuel. My prob however was due to the tank breather. Does it spit fuel if you leave it to evaporate then run it with the fuel tank open ?
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Current half-cars :2004 SV650, VX535 1991
Exes: YBR 125 2007,GPZ500S 1998

[Usher4566]

[renzhuow]

Heard a stuck float can cause the varbs to get too much fuel


https://www.interbankforex.info/kv.gif

[coggie]

ive left it for today, exhaust off and will try again tomorrow, if problem still exists i think float height is next port of call, if its not that then i have no idea.

thanks guys all hep is much appreciated.
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2005 Derbi Gpr Replica, Airsal 70cc kit, K&N, Doppler Racing Crank, Metrakit Pro Carbon Exhaust, Metrakit Carbon Reeds - Currently Being Build (Project)
(SOLD) 2005 Derbi Senda SM Limited Edition 656/999 (SOLD)

[Usher4566]

My bike was doing this .could well be float needle not seeling old worn spring or ruber on top replace it for sake of 7 pound .would not muck around with float hight coz its Probs alright and hard to get right .you will make it too lean or ritch if muck bout with float .float needle is Probs to blame .also if bikes New to you check main jet size is correct .
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New cd200 benly owner

[coggie]

update.

i tried it again the other day,
firstly tried it with exhaust off and it just chucked fuel out from the exhaust port.
it was left with fuel off so I'm not sure whats happening,
the fuel tap does shut the fuel off in the of position,

i then took the carb apart and did notice that the main jet and the needle jet tube (if you get what i mean) wasn't screwed in enough, it was in tight but no all the way in.

i have let it for now and going to try at the week end.

hopefully this will have solved it?

if not where do i go from here?

cheers guys all help is appreciated
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2005 Derbi Gpr Replica, Airsal 70cc kit, K&N, Doppler Racing Crank, Metrakit Pro Carbon Exhaust, Metrakit Carbon Reeds - Currently Being Build (Project)
(SOLD) 2005 Derbi Senda SM Limited Edition 656/999 (SOLD)

[HD]

Well you know its seriously overfuelling.

So I would look at, as you have said already, main jet being screwed all the way in. The needle and its position, if the slide is stuck, the float and its height and also the float needle valve. Should be pointy with no grooves in.
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Rusty '02 Vito Camper + CBR600F3

[coggie]

[HD]

I can't remember now. I did shit loads of reading a while back but basically it allows fuel from the float bowl up I think. Again, wait for someone to come and confirm all of this. Basically the needle has a small circlip on it and several notches as you have probably seen.

If you move the clip onto a different notch it allows more/less fuel through.

Pilot jet controls 0-1/4 throttle, main jet does 1/4 to 3/4 throttle and needle does full throttle. Basically if you put the clip up a notch on the needle, you are allowing more of the needle to go down into the main jet, meaning there is less fuel coming out with the same amount of air. In the same instance, moving the clip down a notch 'raises' the needle allowing more fuel through.

All I would check is if the needle is worn or if it has snapped. To be honest, it still wouldn't be letting through this much fuel so I would say it may not be seated correctly inside the emulsion tube or something. But yeah, have a scout around and let us know how you get on.

Also check your choke is returning as it could be stuck but I doubt that would be chucking that much fuel out, again.

Also, is the bike running when you get all of this fuel or is it only turning over?
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Rusty '02 Vito Camper + CBR600F3

[coggie]

its a brand new carb if this helps

in the picture i uploaded it was running quite nice and smooth, probably just excess in expansion chamber,

in the update i had the exhaust off and spark plug cap off,

ah i basically see, should have really known how the needle works ( completed level 1 and 2 motorcycle and studying level 3)
ill have a dig around the carb again, everything looks fine but doesn't mean it is lol.
ill try over the week end and update.

cheers
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2005 Derbi Gpr Replica, Airsal 70cc kit, K&N, Doppler Racing Crank, Metrakit Pro Carbon Exhaust, Metrakit Carbon Reeds - Currently Being Build (Project)
(SOLD) 2005 Derbi Senda SM Limited Edition 656/999 (SOLD)

[HD]

Sorry yeah, didnt read the first post again. Hopefully you can get this sorted man. Wierd that it will still run with that much excess fuel though

Is your airfilter clean and not blocked?
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Rusty '02 Vito Camper + CBR600F3

[coggie]

brand new k and n air filter too lol

yeah i thought it was weird running ans spitting fuel

hopefully it'll be ok after week end
then just fairing to drill and fit. mot, tax then all good.

EDIT: thanks for your help HD
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2005 Derbi Gpr Replica, Airsal 70cc kit, K&N, Doppler Racing Crank, Metrakit Pro Carbon Exhaust, Metrakit Carbon Reeds - Currently Being Build (Project)
(SOLD) 2005 Derbi Senda SM Limited Edition 656/999 (SOLD)

[coggie]

update.
Problem solved
don't ask me what is was but its fixed after the last carb strip lol

also found out choke is off up and on down even though the instructions said it was on up off down lol

so that wouldn't have helped when trying to start.

thanks guys for all your help

video will be uploaded soon
edit: https://www.youtube.com/watch?v=T4OHXYnJ4ok
____________________
2005 Derbi Gpr Replica, Airsal 70cc kit, K&N, Doppler Racing Crank, Metrakit Pro Carbon Exhaust, Metrakit Carbon Reeds - Currently Being Build (Project)
(SOLD) 2005 Derbi Senda SM Limited Edition 656/999 (SOLD)