Fuel shooting from hole in PHF32

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riccorman
Cucciolo - the Lil Pup
Posts: 20
Joined: Wed Dec 31, 2014 7:11 am
Location: Oklahoma City

Fuel shooting from hole in PHF32

Post by riccorman » Fri Mar 06, 2015 2:40 pm

There is a small hole on the carb body just below the choke mechanism. I rebuilt my carbs and now I have fuel spurting from this hole on my rear carb immediately after hitting the throttle each time. What did I do wrong? Thanks in advance for any and all replies.
-ric
-----------------
1978 Ducati 900 SD Darmah
2001 Ducati ST2
2006 Ducati GT1000
2008 Ducati 1098
2015 Ducati Diavel Titanium #196/500

baddean
Parallel Twin
Posts: 144
Joined: Sun Jun 17, 2007 7:11 pm
Location: Cincinnati Ohio

Re: Fuel shooting from hole in PHF32

Post by baddean » Sat Mar 14, 2015 9:47 am

Ric,
That hole is a vent hole. It allows the float chamber to always be at atmospheric pressure. It is internally open to the float chamber.
Are you sure that the float level is correct in that carb?
Are you using the accelerator pumps or have they been disabled?
If you are using the accelerator pump make sure it is assembled correctly. If it is assembled incorrectly it's possible that when you close the throttle that you could be forcing air pressure back into the float chamber instead of suctioning it out. When you close the throttle the accelerator pump, by returning to rest under spring pressure, recharges itself for the next throttle opening. (diaphragm type)
Are you using a lever or cable for the enriching system? If a cable make sure that the cable is adjusted to close the piston all of the way once the bike is warmed up.
You have excess fuel (or back pressure) at the float chamber somehow because that hole only is open to the float chamber.
That's all I can think of at the moment.
Let us know how it goes.
Hope this helps,
Dean
Faster, faster until the thrill of speed overcomes the fear of death.
Hunter S Thompson RIP

riccorman
Cucciolo - the Lil Pup
Posts: 20
Joined: Wed Dec 31, 2014 7:11 am
Location: Oklahoma City

Re: Fuel shooting from hole in PHF32

Post by riccorman » Sun Mar 15, 2015 10:32 pm

Dean, thank you for your reply. I posted my question after I had reassembled the carbs and initially started the bike. I had not primed the pumps prior to starting it up. They are assembled correctly. After a bit, the fuel squirting from the float bowl vent stopped. I assumed at that time that it might have had something to do with not priming the pumps.

I set about trying to balance the carbs as per Steve's protocol and couldn't get it to idle long enough to complete the first part of the protocol. The front cyl would not fire consistently. I pulled the tank and examined the cables more closely and found that the front choke cable had no free play at all due to the cable routing, and the rear throttle cable was actually too tight for the slide to completely descend. I sorted out the cable routing and I had to remove about a half cm of housing from the rear throttle cable to get some free play there, even after hubbing the adjuster atop the carb. I also went ahead and pulled the carbs back off and dipped the bodies again overnight and examined all the jets again. It turns out that I have mismatched idle jets; the front is a 40 and the rear is a 60. Also, the top of the atomizer on the front carb has a very rough edge to it; almost as if it has been broken. The front carb main jet was also a bit buggered up from the PO's screwdriver. After doing some reading on these forums, I ordered two #62 idle jets from Steve, as well as two new #110 main jets and two AB265 atomizers; they are en route to me now.

We had nice weather this weekend and I REALLY wanted to ride this bike. So... I reassembled the carbs "as is" while I'm waiting for the parts to arrive and was finally able to get the bike idling halfway decently by hubbing the slide screw on the front carb, and after properly setting up the cable free play. Since the initial startup, I have not seen any more fuel coming from the float bowl vent.

After the bike is properly warmed up, it will idle fairly well now, albeit with the front slide jacked all the way up. I'll pull the carbs again when the jets come and hopefully I'll be able to get them balanced properly. The bike runs AMAZINGLY well above 3K rpm as it is now. It is nothing short of exhilarating to ride. And the sound is just incredible. I've owned a ton of bikes, including several newer belt-timed Ducatis, and nothing I've ridden compares to the bevel in terms of the overall riding experience.

Thanks again for your reply Dean, and for all here who have posted in the past and unknowingly helped me with the resurrection of this old bike. I'll post my results when the new jets are installed and carbs balanced.
-ric
-----------------
1978 Ducati 900 SD Darmah
2001 Ducati ST2
2006 Ducati GT1000
2008 Ducati 1098
2015 Ducati Diavel Titanium #196/500

baddean
Parallel Twin
Posts: 144
Joined: Sun Jun 17, 2007 7:11 pm
Location: Cincinnati Ohio

Re: Fuel shooting from hole in PHF32

Post by baddean » Mon Mar 16, 2015 6:48 pm

Glad to hear that you are headed in the right direction.
Dean
Faster, faster until the thrill of speed overcomes the fear of death.
Hunter S Thompson RIP

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