fuel pours out of rear carbie

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cooperplace
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fuel pours out of rear carbie

Post by cooperplace » Tue Jan 03, 2017 6:50 pm

this on an S2. so I thought I'd take off the float chamber and jiggle the needle & seat, but it still does it. i removed the the needle and seat, blew on it, and it seems to seal nicely -I can't blow thru it with the needle gently pushed up against the seat.

But on reassembly, fuel still pours out. maybe the float? Any suggestions would be much appreciated.

cooperplace
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Re: fuel pours out of rear carbie

Post by cooperplace » Tue Jan 03, 2017 7:05 pm

I just tested the float by floating it in metho; it floats just fine. So it's not the float.

I guess I could buy a new needle and seat but I don't want to go to this trouble when it seems to test OK.

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Craig in France
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Re: fuel pours out of rear carbie

Post by Craig in France » Wed Jan 04, 2017 12:59 am

cooperplace wrote:I removed the the needle and seat, blew on it, and it seems to seal nicely - I can't blow thru it with the needle gently pushed up against the seat.
The pressure execised by the floats on the valve is very low. For example, you set the float height with just the weight of the float sealing the valve. That said:

1. It's possible that the float is hanging up when you re-fit the float bowl. Tapping the outside of the bowl - with the handle of a screwdriver, for example - normally resolves this.

2. Change the needle and valve. The tips of the needles go hard over time and stop sealing. So it's good piece of regular maintenance in any event.
(I had to replace 3 at the beginning of last season).

HTH

Craig

cooperplace
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Re: fuel pours out of rear carbie

Post by cooperplace » Wed Jan 04, 2017 2:56 pm

OK, thank you, that makes sense. I'll try tapping with a screwdriver. Can I ask where you get your needle and seat from?
Thanks.

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Re: fuel pours out of rear carbie

Post by cooperplace » Wed Jan 04, 2017 2:59 pm

on bevelheaven there are 2 different float valve assemblies listed:
#300 >#8649.300.33
#250 > #8649.250.33

how do I know which is right for my bike? It's an S2, has a black tip on the needle. PHM40 carbs.

Thanks.

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Re: fuel pours out of rear carbie

Post by BevHevSteve » Wed Jan 04, 2017 4:58 pm

your Ducati with PHM40 carbies will have a #300 float needle valve.
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cooperplace
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Re: fuel pours out of rear carbie

Post by cooperplace » Wed Jan 04, 2017 9:21 pm

darn! I put in a new needle and seat (#300, the correct size) and fuel STILL pours out of the rear carb.

What should I do now?

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Re: fuel pours out of rear carbie

Post by BevHevSteve » Wed Jan 04, 2017 11:42 pm

If float is set correctly at 18mm then change out the float.

You can test this theory by grabbing the float out of the other carb and installing to confirm this is the fix.
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cooperplace
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Re: fuel pours out of rear carbie

Post by cooperplace » Thu Jan 05, 2017 12:02 am

I have a Q about setting the float height. i gather the correct figure is 18mm, but I don't know how to measure this. I've read this:

https://www.dellorto.co.uk/wp-content/u ... tlevel.pdf

but would like some clarification: with the carb opening sitting on a flat surface, should the 18mm measurement be taken with the float just sitting where it sits, or held in the closed position?
thanks

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Re: fuel pours out of rear carbie

Post by cooperplace » Thu Jan 05, 2017 12:29 am

also, under the float valve is a red fiber washer that sits in the carb body. How can get the old one out? It has gone very hard and seems almost welded into the carb body.

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Craig in France
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Re: fuel pours out of rear carbie

Post by Craig in France » Thu Jan 05, 2017 1:11 am

1. The measurement should be taken, "with the float needle just closed”. Using a simple 'Go/No Go' gauge makes life easier. See viewtopic.php?f=26&t=5121&p=21764#p21764

2. You should have received a new fibre gasket with the new float jet/needle. Prise the old one out using a dentist's pick.

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Cheap as chips off eBay etc. Essential workshop tool.

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Re: fuel pours out of rear carbie

Post by cooperplace » Thu Jan 05, 2017 3:13 am

ah, fabulous, wonderful. I already have a dentist's pick: why didn't I think of using it?

Thank you, much appreciated.

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Re: fuel pours out of rear carbie

Post by cooperplace » Thu Jan 05, 2017 5:20 am

Hi Craig, I made the go/no go tool, easy to cut it out of cardboard. Works well! All good now, no fuel pouring out of the carb. Thanks for the great advice; and thanks also to Steve.
Cheers
Peter.

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Craig in France
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Re: fuel pours out of rear carbie

Post by Craig in France » Thu Jan 05, 2017 6:12 am

No worries. Good to hear all is ok and thanks for posting back.

Craig

cooperplace
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Re: fuel pours out of rear carbie

Post by cooperplace » Fri Jan 06, 2017 6:10 pm

there is still a slight weep from the carb, I'm suspecting the gasket on the float bowl. I'll replace that on Monday and see how it goes.

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