New to Ducati - be kind!

discussion about the 750 Sport and '89/'90 900SS, which share many mechanicals with the Paso series
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Danielmc
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model: 750 Sport
year: 1990
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New to Ducati - be kind!

Post by Danielmc »

Hi, decided to add a 1990 750 Sport to my small collection (a '74 BMW R90S and a '78 Moto Guzzi Le Mans 850). I've been lurking here for a bit so thought I should say hello.

The bike I'm looking at has already had 17" wheels fitted, which seems like a bonus, but is running the original Weber carb. I can get a set of second hand 900SS Mikunis, and wondered whether this would be a good modification, and how easy a job it is to swap out the Weber. Will I also need new cables and twistgrip etc?

I'm reassured by the love you guys have for these rarities, and it's great to know such technical expertise is so near at hand.
20YearOwner
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year: 1987
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Re: New to Ducati - be kind!

Post by 20YearOwner »

Why change the Weber?

I now own 2 Ducati PASO 750's they both have there original Webers you can make them work good at both low speed and high speed with adds and modifications.

1st add a fuel regulator available from weber if it does not have one already this makes a big difference, the parts cost is about $75 US.

2nd reduce the coke size by 2 mm and increase the auxiliary ventury by 100 mm, avialable from weber this helps reduce the low speed problems and maitains the high speed performance, the parts cost is about $100 US.

Once you made these modifications you will need to setup the carb. Use your vacuometer to adjust idle and adjust mixture strength. It's a simple four step process.

Good Luck,
Ride safe, have fun and keep the rubber side down.
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paso750
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Re: New to Ducati - be kind!

Post by paso750 »

Daniel, if you don`t enjoy working on the Weber until you get it working a Mikuni is a good modification. It is a reliable and easy maintainance carb.
What you need is the carb manifolds (preferably from a 750SS/Monster if you intend to make an airbox if not it doesn`t matter). You`ll need the two cable twistgrip and the paper seals for the carb manifolds. The original choke lever can be used, not sure if the choke cable is long enough though.
Other than that you`ll need to come up with a solution for the airfilter as the original airbox of course won`t fit and neither will the one from the SS. You`ll probably also have to change the jetting as you may end up with sport filters.
Swapping the carbs is easy.
If you get used ones check the membranes if you can as these harden over time. Imho they are not that cheap as they should be if they need to be replaced.

Btw. instead of adding a fuel pressure regulator you can just get rid of the electric fuel pump and use an underpressure fuel pump from a SS/Monster or Yamaha TDM/TRX850.

G.
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Danielmc
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Re: New to Ducati - be kind!

Post by Danielmc »

Thanks for the replies! I'll be collecting the bike next week so will have a chance then to see if the Weber is as problematic as some rumours suggest. The present owner reckons the only problem he's experienced is a poor tickover, which he was happy to live with.

Bike's done around 30,000 miles and had the belts changed 2,000 miles ago - but this was about two and a half years back. Should I change them as a matter of urgency? Also, apart from fresh oil, are there any (simple!) periodic maintenance tasks that I should be considering? Tyres are good and chain and sprocket were replaced last year.

Must confess that I'd been looking at getting a mid '90s 750SS and wasn't even aware of the earlier 750 Sport Nuovo, but I'm delighted to have bought this one and reckon it looks absolutely gorgeous in the red and silver livery.
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Danielmc
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Pics...

Post by Danielmc »

Bike arrived yesterday (Saturday) and I took a couple of pics...

Image

Image

Image

Image

17 inch wheels and the airbox has been replaced with what looks like a K&N setup. Silencers and front forks from an early 851. New tyres, oil and belts will be done next week.
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ducinthebay
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Re: New to Ducati - be kind!

Post by ducinthebay »

Nice.
Great set of forks. The triple clamps look to be the 851 parts too. Great calipers, also probably from the 851. I would have to assume that he used the clipons from the 851 also since the stock forks were 40mm and the M1R forks are 41.7mm. Front fender is also from the 851. Not quite sure what he did with the front rotors. i think he kept the old 280mm rotors. You should be able to get 300 or 320mm rotors on there if you change the caliper mounts. Better brakes are always better.

What did he do for a speedo drive?

Probably the best set of forks you can put on that bike. The 851 M1R has shorter travel and better valving compared to the Paso M1R forks. I hope he upgraded the shock to match. If not, 900 SS shocks work great.

Did he put a 5.5" rear wheel or the 4.5" rear wheel?

The chrome rings around the instruments are added. The instruments look stock. I would assume he took them to a Speedometer shop to recalibrate for the 17" wheels, and they put on new rings.

Nice pipes. are the GioCaMoto?

Carbon fiber rear hugger looks good on there. Probably from an SS. I see he also put on a matching carbon fiber c/s sprocket cover.

Rubber bands on the frame near the tank are to protect the paint where the forks touch at full lock. I have dents in my tubes there. Make sure the set screws on the lower clamps are set to the same stop angle.

Cam belt covers have been polished, which is a nice touch, and time consuming.

Overall it looks great. Should be a very fun bike for you. Very similar setup to mine. Very stable at speed, and just fun overall. A perfect weekend bike for the mountains. Not a good commuter, unless you are lucky enough to have a mountain range between your house and work.

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.
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Danielmc
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Re: New to Ducati - be kind!

Post by Danielmc »

Hi Phil, and thanks for the words!

I was told by the seller that the forks and triple trees were from an early 851, and it's nice to have your opinion that is indeed the case. Original 280mm rotors have been retained, but I've already heard from Gerhard about swapping these out for something a bit more exotic. I don't know where the Tokico calipers came from, but although my head says keep them my heart would like to see a nice pair of Brembo 4 pots grabbing some semi-floating 300 or 320 Ducati discs.

The rear wheel is a 5.5 and the tyre sizes are currently 120/70 front and 170/60 rear as per the 907ie. As long as I can continue to get 170/60 tyres I see little point in going for a 180. There's a nice Ohlins shock on the back, and the swinging arm is a warranty replacement. Most of the tidying was done by a previous owner a couple decades ago following what seems to have been a crash that did enough damage to write the bike off.

I'm working through a pile of paperwork that seems to suggest that the bike's been regularly maintained and hasn't done many miles in the past few years - current mileage is 30,000 miles. Don't know what the p.o. did with the speedo - there's currently no cable fitted, but there is a new one in a box!

Like I said in an earlier post - I was half looking for a mid 90's 750SS when this bike caught my eye. I think it's a peach and has much more appeal than the more common later bike. I realise that being non-original will mean it's not for the purists, but I love the modifications and see it as a bike that's benefited from improvements made by dipping into the Ducati parts bin to fit stuff they never got around to at the factory.

No commuting for this bike, but it's coming on winter here in the UK, so I'll probably spend the next few months grabbing whatever nice days come my way and hope to have her running and riding nicely in time for next summer.
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ducinthebay
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Re: New to Ducati - be kind!

Post by ducinthebay »

Hmm, didn't notice that they were Tokico calipers. Not bad in any sense. I'd say keep them until you sort out some larger rotors, which means some different adapters for the calipers.

Getting a speedo drive onto the M1R forks with a 17" front wheel is a bit of a trick. The 851 came with 16" wheels when they used the M1R (different speedo drive). The 907 has a 17" front wheel and M1R fork, but the inside of the fork leg on the left side has 10mm(or so) of material removed to allow the space for the speedo drive. I machined mine to get the front wheel centered in the forks. A simple cut to the fork leg, but it took an hour to set it up on the mill to get it straight. Look at what is inside the fork where the speedo drive should be, and also confirm your front wheel is centered in the forks (check the sidewall of the tire to the fork leg)

Overall, how does it ride?

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.
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Danielmc
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model: 750 Sport
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Re: New to Ducati - be kind!

Post by Danielmc »

Though I haven't pushed things because the belts and tyres are old, I can say that the bike is a treat to ride. The suspension is firm but compliant and the light weight of the bike means that it feels plenty powerful with two cylinders and 750cc.

I have been offered some ex-Laverda 320mm discs and calipers and will be attempting to fit these when time allows. Gerhard has posted some technical drawings, and I'm looking around to see who in the UK can make me a pair, but I wondered if it was still possible to buy the adapters anywhere - or whether anyone has a set to sell? Looks like Brembo/MQ used to offer them:

Image
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ducinthebay
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Re: New to Ducati - be kind!

Post by ducinthebay »

Guzzitech has the caliper adapters for sale on e-bay (but oddly not in his regular on line store) Either for 40mm spacing or 65mm spacing calipers. Also sold by loudbikesteve on ebay(in Canada)

I'm sure you can sell your current adaptors and calipers to someone on the list that wants to keep the 16" wheels, but wants better brakes. Hard to beat the feel of cast iron rotors.

If you are looking for new tires, I strongly recommend the new Pirelli Angels. Really light feel to them which will help the Sport turn in just a bit quicker. I have them on the ST4s and was surprised at how fast they turn in compared to the old Diablos (which were no slouch).

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.
900streetfighter
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Re: New to Ducati - be kind!

Post by 900streetfighter »

The M1R forks will take Brembo 4 piston 40mm calipers on the original fixings with no need for adaptors if you fit 320mm brembo discs as per 851 standard set up.
V nice bike, well done.
Cheers, Keith.
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ducinthebay
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Re: New to Ducati - be kind!

Post by ducinthebay »

Hmmm. Good point. That would be the tell if the are 851 forks or Paso forks Time for web search to see what brakes did come on those first year 851s. I think they all had 40mm mount brakes with the black 4 piston calipers. However, I think that the 16" wheel version had 300mm rotors. Plenty of 300 mm rotors out there to choose from. I have a few sets I'll gladly sell you.

Can you measure the pitch on the fork bosses, or take picture of what you have.
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.
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Danielmc
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model: 750 Sport
year: 1990
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Re: New to Ducati - be kind!

Post by Danielmc »

Thanks for the input! I plan to see about a set of Angels (as they still make a 170/60) so it's good to hear from someone who's actually used them.

Here's the front end:

Image

The latest position is as follows: The forks have the mounts for Brembo P8 calipers. This is not insurmountable as I have already sourced a pair of the adapters mentioned previously from Loudbike Steve that should allow Brembo 4 pot calipers to be fitted to either 280mm or 300mm discs. A bigger problem is that there's a 19mm offset on the current disc setup, and no Brembo discs seem to be available that would drop straight on. I have no idea why the setup has such an offset, using as it does a 900SS wheel and 750 Sport discs on alloy carriers. EBC manufacture a couple of semi-floater near matches for old/odd Yamahas, one with a 17.8 offset and a 5mm thick disc and another with an 18.5 offset but with a thicker 5.7mm disc that might require some sanding of the brake pads.

Any ideas?
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ducinthebay
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Re: New to Ducati - be kind!

Post by ducinthebay »

So, the forks are probably not 851 forks, but are from a 750 or 906 Paso. Especially since there is so much fork leg slid up above the triple clamps. No problem, still nice forks. Just for kicks, measure them to confirm that they are 41.7mm.

As for rotors, the offset is needed to meet your caliper. The new caliper will be in different place than the current caliper (inboard/outboard) The stock rotors should fit up just fine. I used the 300mm rotors from Yamahas for years before I upgraded to 300mm cast iron Brembo rotors. Same offset as stock Ducati (brembo)

You can still sell that current caliper/adapter set to another lister.

If you get some stock 320mm rotors, and 4 pot calipers, and the adapter brackets, everything should line up. (should) Mount everything up without the brake pads installed just to confirm the fit of everything and the clearances. You should have no rubbing. Then install the brake pads and open them up all the way, and again, you should have no rubbing.

Confirm that the front wheel is centered in the forks before you go much further. You don't need to get fancy, just shove your finger between the sidewall of the tire and the fork leg on both side to see if it is close. If the wheel is not centered, neither will your rotors. He had to do something to space the wheel correctly as the usual spacer is the speedo drive, and the one for that wheel is too big to center the wheel, and the old one needs some modification to fit. Got a picture?

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.
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Danielmc
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model: 750 Sport
year: 1990
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Re: New to Ducati - be kind!

Post by Danielmc »

Many thanks Phil - I was getting confused!

Fork leg diameter is definitely 41.7mm.

I reckon I'll go with 300mm discs, some 40mm mounting centre Brembos and the adapter brackets from Loudbike and put the whole thing together like you said.
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