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 Post subject: mikuni carb conversion?
PostPosted: Wed Feb 06, 2013 1:03 pm 
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Joined: Sat Oct 27, 2012 5:28 am
Posts: 7
Location: USA
model: 750 Paso
year: 1988
I've been around lurking just reading up, ( I have a Ducati 750 p ) with 4k original miles, I want to do the mikuni swap. Anyone have any pictures around showing how the carbs look once installed?

Don


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 Post subject: Re: mikuni carb conversion?
PostPosted: Wed Feb 06, 2013 1:57 pm 
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paso grand pooh-bah
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Joined: Sun Jul 18, 2004 12:00 am
Posts: 5359
Location: southern Germany
model: 750 Paso
year: 1987
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 Post subject: Re: mikuni carb conversion?
PostPosted: Wed Feb 06, 2013 7:50 pm 
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Joined: Sat Oct 27, 2012 5:28 am
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Location: USA
model: 750 Paso
year: 1988
Great, that you so much . Really gives me an idea of how much room I'm going to have for air filters, any suggestion on what I should use. On the old Weber I had the low profile k & n set-up, but obviously that won't work. Maybe a couple of the ball type foam uni filters?

Thanks again


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 Post subject: Re: mikuni carb conversion?
PostPosted: Wed Feb 06, 2013 7:59 pm 
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Joined: Sat Oct 27, 2012 5:28 am
Posts: 7
Location: USA
model: 750 Paso
year: 1988
I've got a 749 frame sitting around here somewhere, I wonder if the 2 valves motor would fit. Hmmmm. Allot more room under the tank on the 749 for sure.

What I'm doing is converting from a conventional bike to a reverse trike like a can-am spyder.do no too concerned with keeping it pure Paso per say.

Cheers


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 Post subject: Re: mikuni carb conversion?
PostPosted: Wed Feb 06, 2013 8:13 pm 
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paso grand pooh-bah
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Joined: Sun Aug 01, 2004 12:00 am
Posts: 1097
Location: siena, italy
model: 750 Paso
year: 1988
Back to the topic: there're many post about mikuni swapping and air filtrer solution, including mod to the original airbox, longer mainfolds and anything else. Just need to make your own search :thumbup:

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Black "DUKE" 751582
ex...Red "smooth" 753349 :-(


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 Post subject: Re: mikuni carb conversion?
PostPosted: Wed Feb 06, 2013 9:27 pm 
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paso grand pooh-bah
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Joined: Sun Jul 18, 2004 12:00 am
Posts: 5359
Location: southern Germany
model: 750 Paso
year: 1987
you can use UNI filters UP4060A (angled pods, 10cm high)
Image

or the UNI filter UP6060A (same but 15cm high). I`d take these if you have no airbox.

These are K&N SN-2530, once posted on the forum
Image

Or you can modify the original airbox
Image

G.


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 Post subject: Re: mikuni carb conversion?
PostPosted: Wed Feb 27, 2013 10:05 pm 
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Joined: Sun Feb 24, 2013 11:14 pm
Posts: 77
Location: Melbourne Australia
model: other
year: 1995
Would a CV carbed M750SS or M900/SS airbox (with battery box cut off) fit?

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1994 M900 Street
1999 M750 "Scrambler"
2004 GSXR750 Track


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 Post subject: Re: mikuni carb conversion?
PostPosted: Thu Feb 28, 2013 1:30 am 
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paso grand pooh-bah
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Location: Hilltown,Pennsylvania
model: 906 Paso
year: 1990
FYI
any CV carb is a performance downgrade :banghead:

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There's no problem so bad that a little fixing can't make it worse! : )
If it ain't broke keep fixin it till it is
88 750
90 906
92 907ie


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 Post subject: Re: mikuni carb conversion?
PostPosted: Thu Feb 28, 2013 2:24 am 
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Joined: Sun Feb 24, 2013 11:14 pm
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Location: Melbourne Australia
model: other
year: 1995
higgy wrote:
FYI
any CV carb is a performance downgrade :banghead:


I know, but they are civilized, (except when they freeze up in the winter :banghead: ). Also I may be able to get hold of some FCR39s and use a CV carbed airbox with open lid. Looks tight at the front of the frame where it meets the steering head. K&N Pods if I'm desperate.

Do the Webers freeze as badly as the CV carbs? I'm surprised a straight butterfly carb freezes as I've heard they do.

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1999 M750 "Scrambler"
2004 GSXR750 Track


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 Post subject: Re: mikuni carb conversion?
PostPosted: Thu Feb 28, 2013 9:57 am 
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Joined: Sat Oct 27, 2012 5:28 am
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Location: USA
model: 750 Paso
year: 1988
Working carbs vs non-working = upgrade :thumbup:


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 Post subject: Re: mikuni carb conversion?
PostPosted: Fri Mar 08, 2013 9:53 pm 
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Joined: Sun Feb 24, 2013 11:14 pm
Posts: 77
Location: Melbourne Australia
model: other
year: 1995
Doug Lofgren got good performance from the 38 CV carbs with his mods. He doesnt do them anymore concentrating on FI.
He taper bores them, trims the throttle shaft and changes the emulsion tube. He has them working nearly as well as FCRs, but without the snappy response of course.
I am going port a set. I plan to taper the opening, smooth the throttle shaft and knife edge or tear drop the butterfly to reduce turbulence on the "air side". I will port the manifolds and increase their diameter.
I have mucked around with these things before but plan to go a step further.

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1999 M750 "Scrambler"
2004 GSXR750 Track


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 Post subject: Re: mikuni carb conversion?
PostPosted: Sat Mar 09, 2013 12:06 am 
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paso grand pooh-bah
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Location: Hilltown,Pennsylvania
model: 906 Paso
year: 1990
Quote:
nearly as well as FCRs


lot of room for discussion in "nearly" a CV carb will never perform as well as an FCR...but then as stated that depends on what you are looking for..
for everyday riders a cv carb is fine..if you wnat max performance you have 2 choices, the weber or an fcr

_________________
Ducati,making mechanics out of riders since 1946
There's no problem so bad that a little fixing can't make it worse! : )
If it ain't broke keep fixin it till it is
88 750
90 906
92 907ie


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 Post subject: Re: mikuni carb conversion?
PostPosted: Sat Mar 09, 2013 1:13 am 
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Joined: Sun Feb 24, 2013 11:14 pm
Posts: 77
Location: Melbourne Australia
model: other
year: 1995
higgy wrote:
Quote:
nearly as well as FCRs


lot of room for discussion in "nearly" a CV carb will never perform as well as an FCR...but then as stated that depends on what you are looking for..
for everyday riders a cv carb is fine..if you wnat max performance you have 2 choices, the weber or an fcr


True. How long's a piece of string? :D I run FCR 41s on my '95 M900. I would take FCRs over any carb. The FCRs are vastly better than the CVs when I modify the CV38s, but Lofgren really closed the gap on peak power. They will never be as responsive as FCRs, but you should see his dyno charts. Very impressive. But he's alot smarter than I am.

I want to try some of the mods he did, (the ones I can understand, anyway) :mrgreen:

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1999 M750 "Scrambler"
2004 GSXR750 Track


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 Post subject: Re: mikuni carb conversion?
PostPosted: Sun Mar 10, 2013 2:23 am 
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Joined: Sun Feb 24, 2013 11:14 pm
Posts: 77
Location: Melbourne Australia
model: other
year: 1995
If I find a set of used FCR39s for a good price, I will put the CV38s back in the parts box :cool: .

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1994 M900 Street
1999 M750 "Scrambler"
2004 GSXR750 Track


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 Post subject: Re: mikuni carb conversion?
PostPosted: Mon Mar 11, 2013 11:12 pm 
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Joined: Sun Feb 24, 2013 11:14 pm
Posts: 77
Location: Melbourne Australia
model: other
year: 1995
I did some work on some Mikuni CV 38s yesterday.
I disassembled the carbs and gave them a good clean.

I "ported" a bad sharp step in the transition from the carb bellmouth to the throat in front of the butterfly. You cant see it but you can feel it with your fingers. I wanted to promote a smooth airflow into the carb to reduce turbulence which may contribute to CV piston/slide "flutter". I also fitted oem heavy slide springs to help reduce this slide flutter which affects throttle response. I have tried various springs and gone back to the oem springs for this reason.

I fitted new Factory Pro needle jets/emulsion tubes. I have set the float to 14mm, as they are often out of spec from the factory.

I will consult a friend who tunes race cars regarding the throttle butterfies. You can "knife edge" them, "tear drop" (like an airplane wing) them, or just smooth the sharp edges a little, so I wil consult this guy.

I am losing motivation to go the "full monty" on these carbs as a friend may be selling me some FCR39s (and some 900SS cams and 36 degree flywheel). So we shall see.

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1994 M900 Street
1999 M750 "Scrambler"
2004 GSXR750 Track


Last edited by koko64 on Mon Mar 11, 2013 11:38 pm, edited 1 time in total.

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