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| No Jet in my return fuel line http://www.ducatipaso.org/forum/viewtopic.php?f=13&t=4722 |
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| Author: | ir_joep [ Thu Apr 07, 2011 7:35 am ] |
| Post subject: | No Jet in my return fuel line |
Searching, searching, searching the www and this forum I found my bike needs a Jet in the return fuel line which I do not have. I’m running a '90 900 ss with it’s stock 44 DCNF 118 weber in a 750 sport (with 750 sport tank/fuelpump and ignition). No fuel pressure valve in the fuel line. Is this Jet the cause why it does run crap from 1500 to 3500 rpm? The thing is under (hard) acceleration there is no problem. Riding in town between 1500 and 3500 rpm under deceleration and light acceleration it is awful. It is best described as the engine goes on and off. No smooth ride. I use the clutch a lot....which is not a strong feature either. Do not get me wrong I still love these bikes. Under light acceleration in this rpm range the problem also exists. But If I am above 3500 rpm it's ok, except for a very light surge at high speeds (140 km/hr) at steady throttle. Going to 180 km/hr easy. Have not tried further. When I was running the standard 750 engine I had the same problem. I though it would disappear when I installed the 900 but it problem did not go away. Please do not tell me (I hope) this is the infamous weber gap cause what I have been reading people talk about slight hesitation when the wack the throttle open, which I do not have. Please let me have your thoughts. Jet in return fuel line? Thanks JOep |
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| Author: | paso750 [ Thu Apr 07, 2011 7:48 am ] |
| Post subject: | Re: No Jet in my return fuel line |
just curious, are you running an original exhaust and airbox and are you still using the jetting from the 750 and do you have the coil wiring mod ? G. |
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| Author: | ir_joep [ Thu Apr 07, 2011 8:53 am ] |
| Post subject: | Re: No Jet in my return fuel line |
HI, Thanks for your reply. I do no have a coil wiring mod... Do you think I need one? Standard airbox (750) with KN filter 900 ss weber with jetting for a 900 ss (came with the engine and i have checked the jets, venturi etc. with documentation) Exhaust. I'm currently running a 851 kit exhausts (very open). I used to run standard 900SS exhausts Changing exhaust did not change the behavior. I was hoping it would... Cheers Joep |
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| Author: | higgy [ Thu Apr 07, 2011 10:19 am ] |
| Post subject: | Re: No Jet in my return fuel line |
the easiest way to improve this would be to loose the K&N and put the stock filter back Also checking what voltage you have at the coils as G suggested wouldn't hurt or if your check book is fat and healthy and in need of a dietary intervention  there is always our Weber.doc  and FCR's and Mikuni's and the venerable Del(why do I smell gas)orto 
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| Author: | ir_joep [ Thu Apr 07, 2011 12:05 pm ] |
| Post subject: | Re: No Jet in my return fuel line |
Hi Higgy, The Mikuni’s BDST 38 I have do not fit the sport because of the position of the battery. Maybe different manifold are the trick. I will def. look into the coil wiring mod. Is there a short way for testing purpose only where I could run a direct wire to the coils from the battery? The weber.doc- stuff is very useful. But for now I think there is a much bigger problem bugging me which needs to be sorted first. The stock filter is a useful suggestion. I will try that one and the coil wiring mod. Any ideas about the jet in the fuel return??? I think it is a good idea to return to stock as a staring point isn’t it. Cheers Joep |
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| Author: | higgy [ Thu Apr 07, 2011 12:26 pm ] |
| Post subject: | Re: No Jet in my return fuel line |
If memory serves it was a 60 main jet that was used the idea being to keep the fuel pressure up. Weber works best with the pressure maintained at 3PSI. you can also install a holley low pressure regulator instead of the jet. Some have used a cheap variable regulator as well but in my experience the are not well made and leak a lot. There is/was a company making a manifold that moves the mikuni out the side have no idea if it is still made or if it fits your situation. Yeah you could run a wire from the battery just be careful to make it an easily and quickly removable connection in case some unexpected situation comes up Moving the headlight feed to the battery should solve most coil issues as it is the largest sucker of the juice  Do make it a FUSED CONNECTION  alternator connectors tend to fry as well limiting the output and complicating the rest of the trouble prone electrics. Fixing the electrics is always a good place to start when dealing with carb issues on a Ducati. |
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| Author: | ir_joep [ Fri Apr 08, 2011 11:35 am ] |
| Post subject: | Re: No Jet in my return fuel line |
Hi, Thanks for helping. I just bought the bosch relais switch (coil wiring mod) and a 120 main jet of a del'orto as per 750 parts manual. The jet is the same for a 750 and 906, so should be the same for a 900 (no online parts manual available?) having also a 300 fuel stop in the weber. I think i have some time this weekend... JOep |
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| Author: | Duc906 [ Fri Apr 08, 2011 12:28 pm ] |
| Post subject: | Re: No Jet in my return fuel line |
This is what I found when I was replacing the fuel hoses on my 906.It's difficult to make out but the jet is a size 60 jet from Del'orto |
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| Author: | ir_joep [ Fri Apr 08, 2011 12:53 pm ] |
| Post subject: | Re: No Jet in my return fuel line |
Yeah I have been reading this post. Parts catalogue says 120 rather confusing. Does size matter? Cheers Joep |
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| Author: | ir_joep [ Sun Apr 10, 2011 7:45 am ] |
| Post subject: | Re: No Jet in my return fuel line |
Hi, Thanks everybody for helping me out. Got the wiring mod and jet in on Saturday and found that the bike starts easier than before. The 1500-3000 rpm problem has disappeared to a level of which I think is more related to lack of maintenance, like valves adjustment, balancing the weber etc. Maybe try the 60 jet to see if there is any change. But for now RIDE RIDE RIDE (weather is brilliant in the Netherlands at the moment) Cheers Joep |
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