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Author:  stubbie [ Mon Apr 24, 2017 4:57 pm ]
Post subject:  Dellorto

New to forum. I have a 1987 750 Paso with Dellorto carbs. Not sure of size but will check. I have just had them cleaned and re kitted by a local Ducati mechanic. The bike sat for 12 months previous to this so they were all gummed up with old fuel and crud. This past Sunday I took the bike on a 200km run to a motorcycle festival and have found that I'm having a few problems with them.
1/ There is a strong smell of fuel coming from the exhaust and around the general area of the carbs when idling.
2/ The bike stalls sometimes when parked at traffic lights.
3/ The engine seems to run with a (how do I describe it) it's sort of a, barp, barpbarp, barp, barpbarp, barp type of sound. As if it is misfiring. (I'm 59 years old. That sounds almost foolish.)
I have no idea what size jets are in these carbs and the bike has a set of aftermarket mufflers on it. Maybe Staintunes. I've also read on some pages about there needing to be a return or y junction to the stopcock because of to much fuel. Previously I had also heard the ticking from the fuel pump when the ignition was turned on but did not notice that when I turned the bike on today, so maybe the fuel pump has given out. Also the wire has come off from the temp gague. 2 wires in the vicinity I think a white one and a light brown one. Not sure which is correct. I think brown. So I have no idea how hot this bike is running.
Thanks for any help or advice.

Paso%202_zpsbjlr7tqp.jpg [ 176.49 KiB | Viewed 4600 times ]

Author:  stubbie [ Tue Apr 25, 2017 11:30 am ]
Post subject:  Re: Dellorto

Ok so I have been doing a lot more reading. It appears that the fuel pump is not needed with Dellorto's so it's not a problem if it's not working. I also see that it may be a problem with the coils so I will check the voltage there tomorrow.

Author:  paso750 [ Wed Apr 26, 2017 5:14 pm ]
Post subject:  Re: Dellorto

Hello and welcome to the forum and +1 for trying to anwer your questions yourself. :thumbup: Seriously.
Your Dellortos are probably 36s. While some say you can run carbs w/o a fuel pump it's better to stabilize fuel delivery by keeping it and the return hose to the tank. The use of a fuel pressure regulator is quite common to reduce the risk of the carbs overflowing. The use of a vacuum fuel pump is another alternative.

Cloth braided fuel hoses often "sweat" with age which can be another reason for the smell of gasoline.

The wire to the oil temperature sender is the brown one (you find the wiring diagram in the downloads on top of this forum). A white-black one is the power supply of the fuel pump.

Let's see what your voltage is at the coils.

You should get yourself new tires btw.


Author:  stubbie [ Thu Apr 27, 2017 2:26 am ]
Post subject:  Re: Dellorto

Thanks for the reply. I've been looking for vacuum fuel pumps and regulators but not to shure wich ones will work. Do you have any recomendations.

Author:  Mc tool [ Thu Apr 27, 2017 4:09 am ]
Post subject:  Re: Dellorto

Carbed Ducati Monsters were fitted with them . :)

Author:  paso750 [ Thu Apr 27, 2017 9:53 am ]
Post subject:  Re: Dellorto

I like the ones from a Yamaha TDM or TRX better as all connections show in the same direction.
Basically you can use every fuel pump (electric or underpressure) which comes from a carbed 750 or 900cc engine. No matter if it`s a 2 or 4 cylinder.

Author:  stubbie [ Fri Apr 28, 2017 11:14 pm ]
Post subject:  Re: Dellorto

Thanks again. I have just ordered a new vacuum fuel pump. I have new Golden Tyres on the bike by the way. They seem really good so far after 200km. My voltage meter seems to be broken so I will borrow one from work today and see what I get at the coils. It also looks like I am missing some lights on the dashboard so will start working on fixing that also.

Author:  stubbie [ Sun Aug 27, 2017 1:44 am ]
Post subject:  Re: Dellorto

Had my Dellorto's refurbished by a local Ducati dealer but it still doesn't seem to be running correctly. Had a really bad smell of fuel coming from the exhaust and black soot in the exhaust so obviously running to rich. I sent it back to them to take another look but it is still not running right it now doesn't seem to want to idle correctly. What should idle speed be when running Dellorto carbs? Is it 1000 or less Cheers

Author:  whitepaso [ Tue Sep 05, 2017 6:24 pm ]
Post subject:  Re: Dellorto

I have Dellortos on mine and a light gasoline smell is normal to me, at least has always been there on mine (I've owned mine since early 90's), and I've rebuilt my carbs at least twice since then, both times due to worn out float valves due to ethanol in gasoline. The gasoline smell has always been there and they do run a bit on the rich side. I believe they also have the accelerator "pump" which may also make them smell like gasoline. The pump is a mechanical valve that works by dumping fuel into the intake when you whack the throttle open. Maybe there is some unburned gasoline coming out the exhaust. Just theory, no science to back that up.

I will caution you to one thing though that can be really bad, and this is from personal experience. When your front cylinder carburetor float valve goes bad, it can continuously leak gasoline through the carb into your front cylinder and then eventually down into the case. Once the case fills with fuel, it will be hard to start, won't run correctly (constant stall at low rpm) and then will eventually expel engine oil out the crankcase breather behind your rear cylinder - directly onto your rotating tire!! And that's best case. To prevent this from ever happening again I installed an aftermarket fuel shutoff valve immediately after the fuel pump and before the fuel line split to each carb. I use it religiously.

The low idle stall can be adjusted out easily by using the low idle screw on each carb. Adjust each one very gradually (1/8 turn) at a time and alternate from one carb to the other to keep them synchronized. I can't recall my idle rpm but even now and again mine will stall at a stop sign or traffic light, it does have a low rpm. Temperature on any given day seems to make a difference too; warmer is always better for mine than cooler days.

Lastly it's not uncommon to hear your carbs gulping air at idle and your engine thumping and venting away because the carbs, cylinders and crank vent are right below you and there is no sound suppression around any of it. If they have K&N filters it's very audible. Totally normal. Remove your seat with the engine running and it becomes very apparent!

I hope this is helpful. Please post a follow up so we can all learn form your mistakes, er, experience :)

Author:  stubbie [ Fri Sep 22, 2017 1:03 am ]
Post subject:  Re: Dellorto

Thanks Whitepaso. Too late, crankcase lesson learned. Now turn fuel off when I know I wont be using it for a while. Thin oil and fuel coming out of every orifice on the engine. Worked out that the bike won't idle when the choke is open. If I leave the choke off and just let it splutter it eventually runs ok. Need to do some investigation at the carby's re choke connection. Guy at bike shop said that the choke only appears to work on one carb. Uh?

Author:  Antomonster [ Thu May 10, 2018 6:01 pm ]
Post subject:  Re: Dellorto

Effectively with the carburetors, it is not necessary to install a fuel pump.
My motorcycle, with exhaust open, works perfectly with the PHF 36 and the following settings: 142/145, 60, K4-2, 60/3.



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