mikuni carb conversion?

[fasterdammit]

Try them. Also be aware that the manifold for the front is not the same as the one of the rear cylinder.
If they are swapped you`ll see that the top angle of both manifolds doesn`t match.

G., if nobody's told you yet today, you are a gentleman and a scholar.

[brad black]

the mikuni manifolds are the same part number for both cylinders. 750 is 14010071B (2000), 900 is 13710081A (earlier?).

the 900 has a downward angle from the head face flange, as it has to meet in the same place the 600 and 750 manifolds do as carb location is the same on all capacities. the 600 have a "6" stamped at the edge of the head face flange, the 750 a "7". 750 is much the same size internally as the 900, whereas the 600 (and 400) manifolds are smaller internally. it's quite obvious when you see them side by side.

the 600 and 750 manifolds are straight from the head face flange by comparison.

not sure when they started stamping the numbers, haven't checked a 1991 model 750 for instance.

not sure what would happen if you ran 900 manifolds. the vert would try to lower the carbs, the horiz try to move them back, so they should be uneven.

this is a 900: http://www.ebay.com/itm/DUCATI-oem-750- ... 78&vxp=mtr

this is a 750. you can see the 7 too: http://www.ebay.com/itm/1993-Ducati-750 ... 4d&vxp=mtr

found this too! http://www.ebay.com/itm/Horizontal-Cyli ... 7a&vxp=mtr

also, the carbs are subtly different too. i know with the same jetting the original m600 carbs were leaner than the us spec 900 carbs when i did that swap to my 750 motor. just internally drilled passages, that sort of thing. plus there was quite a bit of variation in std jetting, 750ss was all the same, but 750m varied needle jet size depending on year, going from y4 to y2 at least, usually running a 132.5 main. ss always had y6 and a 140 main. so you may find slight variation depending on carb source.

[paso750]

Brad, thanks for the info.
I always thought the 600 and 750 manifolds were identical as the diameter of the carb is. Also I never noticed any number stamped on my old Mikuni manifolds but the ones I recently got have the "7" on them.
750

600



G.

[koko64]

That's the cleanest set of Mikunis I've seen in a long time!

[fasterdammit]

LOL You're not kidding!

So I just test-fit my Mikunis w/ the manifolds from a 900 and yes indeed, they are skewed clockwise (if you were sitting on the bike and looking down on the carbs). But they clear the frame, the pump bracket and everything else.

So my next questions:

• What to do with the crankcase breather? I have a K&N breather/filter which I was going to put on the Monster but haven't, so this is a perfect excuse for it. Can I safely ditch the 3' or so of plumbing (that terminates at the Weber's airbox) along with the black catch-box (which attaches under frame cross-member where the tank bolts on)? My thought was retain the crankcase-to-catchbox tube, attach the K&N filter at the end there & then toss the rest - the catch-box & its airbox feed tube. Does/will this produce a lot of oil misting? Is there a better place to route that breather?
• Can I get away with the Paso's stock single throttle cable, or should I change the throttle to the SS/Monster's push-pull set up? The return spring on the carbs is pretty strong ...
• Do I need to make any accommodations to the fuel pump/lines?
• Manifold/head gaskets ... any fibrous material work? The OEM ones appear to have an imbedded rubber gasket, which the 900 manifolds do not. However, it appears there may have been a small, circular fiber ring as well. Certainly not a 'full-coverage' gasket for the face of the manifold.
• Does the carb need to be mounted/anchored to frame? I didn't try fitting up the gold-colored bracket that held the Weber ...
• Going out to measure the carb mouths for air filters now, although I'll probably just go with the K&Ns.
• What else don't I know, which I'm not asking?

Going off to poke around the site some more, as these questions may have been answered already (apologies) ... this is just stream-of-consciousness after coming in from the garage.

[fasterdammit]

Also, I'm curious what to do with the two 'outlets' on the Mikunis. They're seen in G's pictures here, one coming from between the two carbs near the top, with the wire wound around it. I assume these aren't fuel-returns or anything; just breathers for the carb? Are these the vacuum lines, which would open/close the petcock found under the tank/seat on Monsters (and probably SSes)? In these pictures, both lines appear to terminate in an uncapped bottle - is this a 'dead air' space?

[paso750]

you should get a throttle grip and cables from a SS (with opener or closer). Don`t keep the one from the Paso.

I can`t help with the crankcase breather or the question if it`s necessary to fixate the carb as I kept the airbox which was held in position by the tank.

The last gaskets I bought from Ducati for the carb manifolds were simple paper ones. I made my own before and will continue doing that as I`ve never had any issues.

The top carb diameter is 60mm. The UniFilter UP4060A (or the higher UP6060A) are a great fit.

What else don't I know, which I'm not asking?

Nothing, except if you disassembled the carb as there are some small details to keep an eye on.

Those tubes on the rear of the Mikuni are just 2 beathers with an inline filter. These should end in a vented bottle to prevent any effects of underpressure by air streaming by.
The hose for the float bowl overflow should also end in a small container. (that`s the connection behind the fuel in. The fuel inlet is brown, the overflow connection black)

The vacuum fuel pump and fuel valve (if you have that) are connected to the carb manifolds. Take a look at the Monster parts catalogue. There`re some nice drawings.
https://www.box.com/s/gslivfnzo4d3ak79c ... 98974593/1

G.

[koko64]

LOL You're not kidding!

So I just test-fit my Mikunis w/ the manifolds from a 900 and yes indeed, they are skewed clockwise (if you were sitting on the bike and looking down on the carbs). But they clear the frame, the pump bracket and everything else.

So my next questions:

• What to do with the crankcase breather? I have a K&N breather/filter which I was going to put on the Monster but haven't, so this is a perfect excuse for it. Can I safely ditch the 3' or so of plumbing (that terminates at the Weber's airbox) along with the black catch-box (which attaches under frame cross-member where the tank bolts on)? My thought was retain the crankcase-to-catchbox tube, attach the K&N filter at the end there & then toss the rest - the catch-box & its airbox feed tube. Does/will this produce a lot of oil misting? Is there a better place to route that breather?
• Can I get away with the Paso's stock single throttle cable, or should I change the throttle to the SS/Monster's push-pull set up? The return spring on the carbs is pretty strong ...
• Do I need to make any accommodations to the fuel pump/lines?
• Manifold/head gaskets ... any fibrous material work? The OEM ones appear to have an imbedded rubber gasket, which the 900 manifolds do not. However, it appears there may have been a small, circular fiber ring as well. Certainly not a 'full-coverage' gasket for the face of the manifold.
• Does the carb need to be mounted/anchored to frame? I didn't try fitting up the gold-colored bracket that held the Weber ...
• Going out to measure the carb mouths for air filters now, although I'll probably just go with the K&Ns.
• What else don't I know, which I'm not asking?

Going off to poke around the site some more, as these questions may have been answered already (apologies) ... this is just stream-of-consciousness after coming in from the garage.

Personally I would keep the oil catch box and put the little filter on it. For the virtual crankcase volume reason and safety reasons.
Many SS and Monster owners who run pods have no bracing to the carbs as the manifold rubbers are stiff and strong. When clamped tight there should be no problem. While pods aren't the best performance thing compared to a good airbox, they look awesome, drop weight, possibly let more air to the rear cylinder head, make servicing easier and clean up the space under the tank.

[fasterdammit]

Personally I would keep the oil catch box and put the little filter on it. For the virtual crankcase volume reason and safety reasons.
Many SS and Monster owners who run pods have no bracing to the carbs as the manifold rubbers are stiff and strong. When clamped tight there should be no problem. While pods aren't the best performance thing compared to a good airbox, they look awesome, drop weight, possibly let more air to the rear cylinder head, make servicing easier and clean up the space under the tank.

Good idea about keeping the catch-box. There's plenty of room to hang the filter off the exit.

I thought the carbs felt pretty secure when I test-fit them, and I hadn't even clamped things down, so that's exactly the news I was hoping for. Tidy!

Wish I had the patience/means to fab an airbox, if the pods are going to be a detriment. There is a carbon fibre shop near my house, but I'll be honest - I'm more interested in getting the thing up & running at the moment. If I were to fab a shroud around the 2 filters, would that improve things at all, or should I not bother unless I'm build a complete box?

Had to chuckle - the pods do look awesome - too bad nobody'll ever see 'em! It's definitely a lot neater in there w/o the Weber & the box.

Just FYI, the K&N SN-2530 pods are $58 on K&N's site, but I found them for $55 on AdvanceAuto's site, with free shipping was able to use two coupon codes - one to knock off 20%, the other for a $25 gift card for my purchase.

Update on carbs: wound up getting them from amazon.com - $72 shipped, for the pair!

Gerhard - thank you for the Monster carb breakdown link! Very helpful indeed - part numbers! I don't have the Monster petcock/pump setup on the Paso (and oddly enough, I've just ordered that petcock for the Monster as mine crapped out - $50, coming from IT) ... I was wondering if I should incorporate them into my setup though. But I think I'll see how it's going to run as-is first (unless it's known that they'll be sorely missed). As I said - the petcock is $50; according to Ducati Omaha's online part store, the pump assly is ~$170

More as it happens; waiting on parts now ... :-\

[paso750]

I`ve been playing with three Mikunis myself yesterday and today as it`s finally nice and sunny outside.

As a consequence and as experience proves itself again I have to say something to all that plan a Mikuni conversion and get used carbs from ebay or anywhere else. Before putting the carbs on the bike disassemble them and write down all jets and needles. Most sellers don`t even seem to know which bikes they are from.
I recently bought one from ebay that was said to come from a 750SS.
As I made myself an Excel sheet long time ago with the jetting overview of Monster/SS/Elefant I can usually determine quite fast which Duc/Cagiva the carb actually came from and if the jetting was right. In this case though the needles were 5C17 instead of 5C19, the main jets were 132,5 instead of 140 and the main air jet which should be a 70 was a 49 on one side and 73 on the other
The next thing is that right next to the membrane there should be a small o-ring (#9 Tav.19) (not on the Mikunis coming from a Yamaha TDM/TRX). These were in place but before the spring of the idle mixture screw there should be a tiny washer and an o-ring (the o-ring has an inner diameter of 3mm and the washer just protects it from the spring). The o-ring and the washer were missing probably in 7 out of 10 carbs I rebuilt. (they are #11 & 12 on Tav.18 of the Monster parts catalogue)
So always take a close look, you never know what the last owner(s) did.
They might have lost the parts while cleaning the carbs or forgotten them on the workbench when reassembling them. Who knows. Always check yourself !

G.

[paso750]

Oh, is there anyone with a spare float chamber cover ?

G.

[koko64]

Oh, is there anyone with a spare float chamber cover ?

G.

Power-barn.com (excellent service & communication)

Allensperformance.com

They have rebuild kits and parts.

[MarkST]

I hate it when interesting threads like this just come to an abrupt stop and you never get to know what the final outcome was . . .