del lorto's on a 750 sport

discussion about the 750 Sport and '89/'90 900SS, which share many mechanicals with the Paso series
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lodola235
Posts: 7
Joined: Mon Dec 07, 2015 6:16 pm
model: intending to buy a Paso/Sport
year: 1999
Location: Belgium

del lorto's on a 750 sport

Post by lodola235 »

Hi, I've gbought an750 of 90 in reasonable state,
my problem is it doesn't start cold unless i use start pilot, i've heard that the Weber carb is an pain in the ass
I still have two brand new del lorto's with accelerator pumps, but they are 32 mm.
my question is can I bore them to 36 on my lathe or will i destroy them doing that,
and at what angle can i mount them on my motor without having problems with the float level or do i have to modify if the are too much at angle ?
can't wait to ride my duc? going troug the paper issues first

thanks in advance
Bart
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Mc tool
paso grand pooh-bah
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Joined: Wed Dec 05, 2007 12:35 am
model: 906 Paso
year: 1990
Location: Newzealand

Re: del lorto's on a 750 sport

Post by Mc tool »

Its not unusual to need the cold start device to start the engine when cold . Dunno about boring 4mm out of a carb , I guess the 1st thing to do would be to measure the slide diameter as it that's not at least 38mm then boring to 36mm is out of the question , and then there are other things to consider , personally I would get a pair of 36mm carbs if that's what you want . Having said that I would 1st give the weber a good clean out and see how it goes . There is a heap of info available here on how to modify/tune the weber and get it behaving a bit better . I think its worth giving the weber a decent try as there is a lot of FAB to get other carbs fitted ( manifolds ) and tuned .
I wish I was young again............Id be heaps smarter than last time
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Derek
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Re: del lorto's on a 750 sport

Post by Derek »

The Dell Orto PHF series covers choke sizes from 30mm to 36mm and all use the same components including the slides. So theoretically, yes you could bore them. I wouldn't want destroy a pair of good carbs though if I got it wrong :shock:
I don't know how far you can tilt them. I'd think about 45º would be the max.
1994 907ie
2017 Supersport 939
2015 Scrambler Classic
1982 Pantah 500SL (now sold)


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Mc tool
paso grand pooh-bah
Posts: 1874
Joined: Wed Dec 05, 2007 12:35 am
model: 906 Paso
year: 1990
Location: Newzealand

Re: del lorto's on a 750 sport

Post by Mc tool »

Derek wrote:The Dell Orto PHF series covers choke sizes from 30mm to 36mm and all use the same components including the slides.
Ahh , I didn't know that , stands to reason then that there wouldn't be any air/fuel passages in the carb body that are in the way ............maybe :)
I wish I was young again............Id be heaps smarter than last time
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ducinthebay
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model: 750 Sport
year: 1990
Location: SF Bay Area

Re: del lorto's on a 750 sport

Post by ducinthebay »

The 32's will run just fine. The only place you will miss out a bit is in the top end. It will carburate just fine at idle and mid range. I doubt you will be pinning the redline on a 25 year old bike anyway. Think of it as a rev limiter of sorts.

Here is a link to a tuning guide for the Dellorto's.
http://danskkartingcenter.dk/dellorto_m ... _guide.pdf
Looks like 40 degrees is max tilt on the Dells.

Manifolds can still be had from Mallosi, and run about $150. Or you can salvage some from a Pantah motor. Get new o-rings if you get some used ones, and don't be tempted to use some RTV to seal them to the head, as new fuels will degrade the RTV in a year or so and you will be plagued with air leaks that will make tuning a pain in the ass. (a nugget of knowledge gifted to me from a previous owner)

Cheers, Phil
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.
lodola235
Posts: 7
Joined: Mon Dec 07, 2015 6:16 pm
model: intending to buy a Paso/Sport
year: 1999
Location: Belgium

Re: del lorto's on a 750 sport

Post by lodola235 »

some news on my beautifull duc

I've bought an set of mikuni's with the acording manifolds and K&N's,
duc starts magnificent, runs better seems a bit too rich, but i' haven't let the carbs syncronised yet, so expect to be better afther, all that in order to have more time to decide if an reversed head and dellortho's or just the carbs .
by the way still busy with the registrating problems so i have some time.
hope it will be an relaible bike i ride sporty but don't race
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ducinthebay
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model: 750 Sport
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Re: del lorto's on a 750 sport

Post by ducinthebay »

That works too. A fairly cheap and reliable solution, that almost always works well.

Phil
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.
lodola235
Posts: 7
Joined: Mon Dec 07, 2015 6:16 pm
model: intending to buy a Paso/Sport
year: 1999
Location: Belgium

Re: del lorto's on a 750 sport

Post by lodola235 »

Hi,
the battery of my sport 750 doesn't work any more ; so i've looked around, and
an lion ion is about 395 (!!) euro's and weights 1.2 kg (!!!!!!) with the high place it has, weight is important
an gel battery is 86 euro and weights 4.5 kgrs
and care free is 101 euro and weights 7 kgrs
and an 'normal' battery 75 euro and 5 kgrs,
any one has an gel and is he ok with ? that seems the reasonable solution for me : no leakage and resonable price
plus i've read that some people mount an modern voltage regulator,does that make any sense ?
lodola235
Posts: 7
Joined: Mon Dec 07, 2015 6:16 pm
model: intending to buy a Paso/Sport
year: 1999
Location: Belgium

Re: del lorto's on a 750 sport

Post by lodola235 »

Hi,
the battery of my sport 750 doesn't work any more ; so i've looked around, and
an lion ion is about 395 (!!) euro's and weights 1.2 kg (!!!!!!) with the high place it has, weight is important
an gel battery is 86 euro and weights 4.5 kgrs
and care free is 101 euro and weights 7 kgrs
and an 'normal' battery 75 euro and 5 kgrs,
any one has an gel and is he ok with ? that seems the reasonable solution for me : no leakage and resonable price
plus i've read that some people mount an modern voltage regulator,does that make any sense ?
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