Restarting the original

[enginerd]

Funny you mention changing the carbs.... Just recently acquired these in 39mm form. Got a Mikuni fuel pump and vacuum petcock from a monster to help with the fueling situation. Oh and the intake manifold is from a 750, stamped as such.

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[Mc tool]

The Weber was a smog carb and should never have been used.

DCNF carbs were fitted to a lot of cars (ie V12 Ferrari's ) none of which could be called smog cars or engines .
In their day ( pre fuel injection ) the Weber was the "go to " carb for hi performance engines .
How did you come to the conclusion it was a "smog carb " ?

[higgy]

What he said

not a smog carb at all.

[enginerd]

Hi Enginerd, if you're on a budget my tip would be to build a carb synchronization tool yourself using just two bottles and a few meters of transparent fuel line. Dirt cheap but pretty effective. That's how I synchronized the Weber on my Paso and it runs as fine as the original set up allows. Here's an informative Youtube video on how to build such a tool: https://www.youtube.com/watch?v=Y_WDF6glD5k

Thanks for the video link. What he did was, pretty novel I must say. The engineer in me is going nuts with ideas to verify balance between two cylinders with liquids. Think I should be able to figure something out here.

[Mc tool]

Google up manometer , basically a U shaped tube.
If your going to use water with an open container make sure you have a fair height as water dont weigh as much as mercury ( which is why they dont use water ) coz if you dont when you kick her in the guts it will suck all the water straight into the motor , which is why the U tube is better but it still needs to be high , like hang it from a roof beam . You could use light oil instead of water to dampen things a bit .
I have just bought off Temu a carb balancer for a hundred bucks .......looks identical to the 250 dollar one in the bike mag ......... so, ah Ill let you know how it goes , mostly for my outboard at this stage .
I have mercury colomb ones but I think moisture has got in there somehow as the mercury has weird looking bubbles in it , I keep forgetting to leave it out in the sun

[Mc tool]

Oh yeah , you could try a version of the BMW plan .
My R80 book advised that if you get bike hot and idling pull one plug lead off and it should fire 3 times and stall , if goes more than 3 close the other carbs idle, less than 3 open it a bit , and repeat for other cyl . Sounds dodgy but I did it and when checked with the ( then working ) mercury colomb meter I didnt have to adjust ballance just the idle speed .

[enginerd]

Thanks for the information an ideas for carb sync tool. I'll see what I come up with when I'm ready to do that. Until then, this should help me out with the carbs.

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Now that I'll be needed the push/pull throttle tube, I opted against the Motion Pro unit and picked up one of these Domino XM2 throttle tubes with custom length cables. Treatland was having a 15% off sale right now so I couldn't resist as I would be needing one anyways. Oh ya, couldn't decide if I wanted to upgrade the grips or keep the vintage OEM pieces but I just happen to have these laying around from building my RS50 a few years ago.

I won't be cutting the cables until I've fitted a new master cylinder I think. Looking at either the 999 or 848 master cylinders for better braking. I'll be looking into the 40 or 65mm gold front brakes for the forks as well. In that case I might end up making my own adapter for them. Kinda kicking myself I missed the auction on a set of 40mm golf calipers WITH adapters for the fork.

Speaking of brakes, I wonder if there is any other type of rear brake I could upgrade to. Hmm.

[enginerd]

Did a little test fitting of the new carbs. Need to fully tighten it down still but it's a little squeeze in there. Now to get some Uni Filters, well that's what this guy did on his 906 with the FCR's and they fit sooooo should for me right? Though he went split FCR's and I went banked so I hope that's the filter I'll need or can use. Making an air box might be a long time coming for this.

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I can probably shimmy the carb over a few millimeters so there isn't contact here. I just installed everything for testing clearance right now, plus to get it off my work bench. The rod moves smoothly at least.

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[enginerd]

After a little bit of research, it looks as though I might have to snag a set of the 900 intake manifolds as they according to some people online sit a little bit lower. That should help me with some clearance issues if can't figure the pod filter that I need. The 750's are much straighter inlet where as the 900's have more of a bend to them. Hmm...

[Mc tool]

Im pretty sure the 900 manifolds are diff , sorta have to be as the heads are further apart .And make sure you get them on the correct head as they are not the same as each other

[enginerd]

I wonder if I was given two of the same cylinder manifolds, despite the auction showing front and rear, labeled as such even. The casting lines, burr removal, stamping is identical for both. I'd think even stamping of the number 7 might be off. I used an aluminum block I had laying around to show difference in the plane that the carb sits on. I then used a steel rule in the last picture so you can see there is a gap towards the middle on both orientations.

In this first picture, the block I have on top isn't pushed to the edge like it is in the picture after. I did this to show the gap, which looks to be the same in picture #3 when I had them flipped around.

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[enginerd]

Well fancy that, according to the Parts Republik website and schematic, they are the same.

Front and rear there is no difference.

Of course the more I think about it, I'm also assuming that Ducati never changed the mounting angle through the years. Given all the changes to the motor in the bikes, I'm betting they did change the mounting angle of the intake for the carbs and such. Maybe this is where split carbs would be beneficial vs racked given the angles. Of course we're talking about a rubber boot that could compensate for angular variance here. More of a perfection annoyance than anything.


I wonder if I update the heads from another model it might help here...

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[Mc tool]

Im not convinced . I dont recall the brass nipple facing inwards . I have a pair of 900ss intake manifolds I could dig out and photo for you . I know for sure they are a pair of 900 manifolds coz I took them off the motor

[enginerd]

On another note for a project on this bike, making some gold Brembo adapters for 65mm spacing. There's some out of Australia for $190 shipped but I think I can get it done for less. Sketched up the part in 3D software, transferred to my 3d printer and printed out a copy now. Now I just need to buy a set of calipers as they're more readily available than the 40mm pieces and in better shape. Not too bad for 2hrs time from initial drawing to printing out a copy I have in my hand.

As long as I can get access to a mill to drill out the bolt pattern from a chunk of aluminum, I can spot face to the depth needed on the holes for the correct offsets of the calipers. I can figure it out one way or another.

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[Tamburinifan]

"Maybe this is where split carbs would be beneficial vs racked given the angles."

Split for more power and higher revs.