Overflowing Carb

Post your 'Carburettor & Fuel System' FAQs, comments & questions regarding Ducati motorcycles here.
killfile
Cucciolo - the Lil Pup
Posts: 23
Joined: Sat Jul 28, 2018 5:16 pm

Overflowing Carb

Post by killfile » Tue Aug 21, 2018 2:26 pm

Folks,
Just fixed my fuel tap so that it now works, but my rear carb is overflowing. Doesn't happen every time. Choke plunger seems okay. Float and needle seem okay (but ill replace needle and seat anyway). I tried turning on the gas while the float bowl wasn't on and it didn't seem to be overflowing from the needle. Is there something else I should be looking for?
The choke jet was clogged, would that affect it?
First time working on dellortos again since I was a kid...
Cheers!

Edit: This is for PHF32As on a 75 860 GT

wdietz186
Cagiva Alazzura
Posts: 703
Joined: Sun Sep 10, 2006 5:40 pm

Re: Overflowing Carb

Post by wdietz186 » Tue Aug 21, 2018 6:41 pm

It's usually dirt in the float needle/seat assy. A little speck of junk will hold the needle off of the seat enough to cause a flood. Sometimes the float can stick on the pivot pin if the bike has sat for a long time and the fuel evaporated away. Sounds like time for a carb clean.

killfile
Cucciolo - the Lil Pup
Posts: 23
Joined: Sat Jul 28, 2018 5:16 pm

Re: Overflowing Carb

Post by killfile » Wed Aug 22, 2018 9:57 am

wdietz, thanks for the reply.

I've swapped out the float and seat, and they are currently seating correctly and I have tested to see that the fuel overflow isn't coming from there.
I've also swapped out the choke plunger, and cleaned out the choke jet.
Float height is now correctly set and appeared to have been incorrect with the previous needle.

I hooked up the choke and the fuel line and turned the gas on with the float needle closed and still getting gas coming out of the carb. I don't understand the internal pathways here, is it possible for the gas to be entering the float bowl area from anywhere other than the choke jet or float needle? I'm not sure of the function of the non-return valve in the float bowl, should I be suspicious of this item?

I'm letting it dry off to see if I can check if it is now leaking from the fuel banjo on the exterior instead of internally.

User avatar
BevHevSteve
SITE OWNER
SITE OWNER
Posts: 2183
Joined: Wed Mar 10, 2004 8:53 pm
Location: Lafayette, California
Contact:

Re: Overflowing Carb

Post by BevHevSteve » Wed Aug 22, 2018 10:35 am

there are 2 non returns both with little balls inside, make sure they both are free to move.

The non return on the pump housing has a PLASTIC ball with a spring make sure you do not force and puncture the ball. It will either move or not. if it doesn't move spray some carb cleaner in there a couple times and try again until it does free up.

The non return that screws into the bottom of the carb has a check ball. Blow through it both ways. 1 direction should be free, blowing on the other end the ball should seal up. If it doesn't shut off the flow spray cleaner inside and shake, repeat, and test until it does. Fix it or replace it.
Image
Steve Allen (925)798-BEVL[2385] Ride'm, Don't Hide'm
Ducati/Euro Spares -> https://Store.BevelHeaven.com
Facebook > http://facebook.com/Bevel.Heaven
Twitter > http://www.Twitter.com/BevelHeaven

killfile
Cucciolo - the Lil Pup
Posts: 23
Joined: Sat Jul 28, 2018 5:16 pm

Re: Overflowing Carb

Post by killfile » Wed Aug 22, 2018 11:03 am

Perfect, investigating the lower no return valve next, thanks!

wdietz186
Cagiva Alazzura
Posts: 703
Joined: Sun Sep 10, 2006 5:40 pm

Re: Overflowing Carb

Post by wdietz186 » Wed Aug 22, 2018 11:15 am

There is only one way into the carb for the fuel to enter, through the banjo and into the passage going to the needle and seat. The check valves are both fed from the float bowl, after the float needle. If you have the plastic banjos on the ends of the fuel lines they may be cracked. It only takes a hairline split to dribble a significant amount of fuel. I believe Steve can supply you with the metal banjo fittings. They are a good idea no matter what, as they always crack when it is least convenient.

User avatar
BevHevSteve
SITE OWNER
SITE OWNER
Posts: 2183
Joined: Wed Mar 10, 2004 8:53 pm
Location: Lafayette, California
Contact:

Re: Overflowing Carb

Post by BevHevSteve » Wed Aug 22, 2018 11:42 am

Image
Steve Allen (925)798-BEVL[2385] Ride'm, Don't Hide'm
Ducati/Euro Spares -> https://Store.BevelHeaven.com
Facebook > http://facebook.com/Bevel.Heaven
Twitter > http://www.Twitter.com/BevelHeaven

killfile
Cucciolo - the Lil Pup
Posts: 23
Joined: Sat Jul 28, 2018 5:16 pm

Re: Overflowing Carb

Post by killfile » Wed Aug 22, 2018 1:38 pm

wdietz186 wrote:
Wed Aug 22, 2018 11:15 am
There is only one way into the carb for the fuel to enter, through the banjo and into the passage going to the needle and seat. The check valves are both fed from the float bowl, after the float needle. If you have the plastic banjos on the ends of the fuel lines they may be cracked. It only takes a hairline split to dribble a significant amount of fuel. I believe Steve can supply you with the metal banjo fittings. They are a good idea no matter what, as they always crack when it is least convenient.
wdietz, thanks for this. The issue is with my rear carb. It had a plastic banjo when I received it, which is now on the front carb (and not leaking) while the rear leaky carb now has the metal banjo from the front carb.

thank you for the help, I'm getting a bit frustrated. I had the bike all together without the tank and it was running perfectly two days ago with my aux fuel reservoir and the overflowing issue didn't seem to be present.

ducadini
860 GT / GTS
Posts: 250
Joined: Sat Jul 31, 2004 9:54 am
Location: Antwerpen

Re: Overflowing Carb

Post by ducadini » Wed Aug 22, 2018 11:40 pm

Is the seat of the needle tight and the little washerin good condition ?
When it isn't tight, fuel can dribble past it and overfill the bowl.
I recently read something of a float that wasn't freely moving all the way down to up. So that it got stuck when down and didn't close the fuelinlet.
When it was halfway, it moved free and closed the fuelinlet.

ciao
ducadini
Nego i ricordi peggiori
Richiamo i migliori pensieri

User avatar
Craig in France
Cagiva Gran Canyon
Posts: 874
Joined: Tue Mar 23, 2004 3:58 pm
Location: Montpellier, France

Re: Overflowing Carb

Post by Craig in France » Thu Aug 23, 2018 6:46 am

ducadini wrote:
Wed Aug 22, 2018 11:40 pm
<snip> ... and the little washer in good condition ?
Dell2.jpg
And don't forget to remove the old one ... :doh:
ducadini wrote:
Wed Aug 22, 2018 11:40 pm
I recently read something of a float that wasn't freely moving all the way, down to up.
Not uncommon. Try tapping the side of the float bowl to release the float.

User avatar
Craig in France
Cagiva Gran Canyon
Posts: 874
Joined: Tue Mar 23, 2004 3:58 pm
Location: Montpellier, France

Re: Overflowing Carb

Post by Craig in France » Thu Aug 23, 2018 6:52 am

killfile wrote:
Wed Aug 22, 2018 9:57 am
Float height is now correctly set ... <snip>
What height did you set it to?
killfile wrote:
Wed Aug 22, 2018 9:57 am
<snip> ... is it possible for the gas to be entering the float bowl area from anywhere other than the {cut} float needle?
No.
killfile wrote:
Wed Aug 22, 2018 9:57 am
I'm not sure of the function of the non-return valve in the float bowl, should I be suspicious of this item?
No.

killfile
Cucciolo - the Lil Pup
Posts: 23
Joined: Sat Jul 28, 2018 5:16 pm

Re: Overflowing Carb

Post by killfile » Thu Aug 23, 2018 11:09 am

Thanks for all the feedback folks.
I've tried swapping the banjos and the same carb leaks every time.
I made my own measurement tool to confirm the 18mm float height setting and measured according the the sideways diagram that BH/Steve shares.
I used the correct fiber washer between the seat and carb.

I discovered that the banjos do not appear to be seating right into the rear carb. I did another test late last night and it appears that I can get it to seat properly with a lot of fiddling. I'll be ordering new banjos (just to have spares). I'm also discovering that my fuel tap threads are so loose that it also won't seal even with plumbers tape. Time to try the permetex and hopefully I'm one more step towards a gas holding bike. I'm hoping to reassemble the carb tonight to resolve, fingers crossed.

Thanks again for the help.

User avatar
Craig in France
Cagiva Gran Canyon
Posts: 874
Joined: Tue Mar 23, 2004 3:58 pm
Location: Montpellier, France

Re: Overflowing Carb

Post by Craig in France » Fri Aug 24, 2018 12:51 am

killfile wrote:
Thu Aug 23, 2018 11:09 am
I discovered that the banjos do not appear to be seating right into the rear carb. I did another test late last night and it appears that I can get it to seat properly with a lot of fiddling.
Stupid question ...

You do have the fuel filters in place? And the felt washers under the bolts? I know if you don't,fuel pisses everywhere ... :shock:
Banjo seals.jpg
Banjo seals.jpg (2.58 KiB) Viewed 4109 times

Image

killfile
Cucciolo - the Lil Pup
Posts: 23
Joined: Sat Jul 28, 2018 5:16 pm

Re: Overflowing Carb

Post by killfile » Fri Aug 31, 2018 2:59 am

Yep, got all the right pieces in place, the banjos just have some difficulty seating properly on that carb.
I've injured my leg and can't kick the bike over at the moment, but I should have another update soon.
I was able to take the bike out for a spin last weekend without too much issue, so baby steps towards all buttoned up.

killfile
Cucciolo - the Lil Pup
Posts: 23
Joined: Sat Jul 28, 2018 5:16 pm

Re: Overflowing Carb

Post by killfile » Tue Sep 11, 2018 10:53 pm

Hey all,
Thanks for all the feedback.
It turns out the crazy leaking carb that I went through twice was only a quarter of the problem. It was solved by a new seat and needle that corrected the float height. The main leak was an ill-seating fuel banjo that was fixed by a closer eye and a delrin. It also didn't help that it appeared to have a bit of a sandy substance mixed into gas at the bottom of the carb.
In addition to all this, my fuel tap leaked like crazy and it wasn't mating with the tank properly. Those are fixed, but I'm afraid the replacement sugar cube fuel taps are allowing the rubber seal to spin inside. So I've scrapped the leaky one to replace it with an original version and updated rubber seal.
Fixed all this and managed to snap my clutch cable. Luckily I'd already ordered a spare from Steve, now it's time to replace the backup!
All of this still didn't get me running right and I was losing a cylinder. Finally pulled the other carb to see what kind of trouble was happening inside. This one ended up having super thick mixture of what almost looked like honey mixed with sand. yuck. Just took it out for a spin now that its all cleaned up and everything is much better. It isn't running perfectly, but it is finally reliable. Now I need to balance and adjust the carbs and I should be solid.
Thanks again for all the help.

Now that I'm writing this, I'm worried that perhaps the grit in the carbs is coming from the K&N filters that are on it from the previous owner. He had it for 10-12 years, and I'm assuming they are that old. Anyone experience this kind of grit in your carbs from K&Ns? I'm thinking I should go order another set right now to avoid the potential issue.

Post Reply

Return to “Carburettor & Fuel System Shop”