750 Sport restoration project

discussion about the 750 Sport and '89/'90 900SS, which share many mechanicals with the Paso series
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paso750
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Joined: Sun Jul 18, 2004 12:00 am
model: 750 Paso
year: 1987
Location: southern Germany

Re: 750 Sport restoration project

Post by paso750 »

Yes, that's the one.

Using the G clamp is good. Be careful not to scratch the cover tho. I had mine in a bench vice just to break the piston loose. Not to push it in. The rest I did connecting it to an old brake pump I still had. It took quite some time as the piston wouldn't budge at all.
What you could try overnight is to put the G clamp on as well. The combination of pressure and penetrating oil might help. Maybe tomorrow add some heat to that.

The number of the V seal is in the P750 FAQs were all the info about the clutch piston is.
Andrew2
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model: 750 Sport
year: 1988
Location: Wollongong,Australia

Re: 750 Sport restoration project

Post by Andrew2 »

I had a piece of wood on the cover side and a used a G clamp and correct sized socket. I have the clutch lever pulled in and strapped to bar overnight. I'm guessing it's the 93040091A seal.
I'm thinking I'll have to end up removing the cover and put it in a vice like you did. I'll have to take the clutch pack out to as they look a bit rusty. As I said when I started the project the bike was near the ocean in a small tin shed which is why the piston is seized and the pack has surface rust. I'm still amazed that the salt got into the clutch area. I haven't looked but there must ba a vent in the cover?.
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paso750
paso grand pooh-bah
Posts: 5505
Joined: Sun Jul 18, 2004 12:00 am
model: 750 Paso
year: 1987
Location: southern Germany

Re: 750 Sport restoration project

Post by paso750 »

I'd prefer the G clamp to the strapped clutch lever. I'd usually do the latter to get remaining air bubbles out of the system.
Have you put something over the cover just in case the piston would pop out over night? (which it probably won't)
The cover is closed. But humidity or temperature changes can cause condensation which could lead to rust.
Yes, the number is the correct one.
Andrew2
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Joined: Thu Oct 27, 2011 7:47 am
model: 750 Sport
year: 1988
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Re: 750 Sport restoration project

Post by Andrew2 »

The cover is facing up with a rag over it just in case but like you say I doubt it'll come loose overnight. I'll get online tomorrow and order a new seal. Hopefully the piston and bore will clean up ok. I was surprised it was a bit rusty, I thought the piston would have been stainless.
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paso750
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Joined: Sun Jul 18, 2004 12:00 am
model: 750 Paso
year: 1987
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Re: 750 Sport restoration project

Post by paso750 »

I have to correct myself. There are two small cutouts on the bottom of the cover.
Stainless would be nice but unfortunately they aren't. If I remember correctly the rusted ones I had were all of this type. Mine were quite strongly pitted and the surface looked a bit like chrome. The others look different.
Andrew2
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model: 750 Sport
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Re: 750 Sport restoration project

Post by Andrew2 »

That would explain the corrosion. Were the pitted ones usable or did you have to throw them away. I'm thinking mine might be badly pitted.
Andrew2
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model: 750 Sport
year: 1988
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Re: 750 Sport restoration project

Post by Andrew2 »

Success. I just went out to the garage and it was still stuck firm so I put a lot more heat and penetrating oil on it and still nothing but after pumping the clutch lever for a while it started moving and has now moved 5-6mm and will pop right out but I've left where it is for the moment. It looks like it's just rusty on the top part that was exposed and what has come out seems to be ok but I won't know for sure until I remove it completely.
Is there anything I should do next before pulling it all the way out. The cover is still attached to the bike at present. Can I do what needs to be done without detaching the cover from the clutch hose....I suppose I'll lose all the clutch fluid anyway so I may as well disconnect it and put it on the bench. It'll make the job easier.

Image

Check out the clutch pack lol
Image
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paso750
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Joined: Sun Jul 18, 2004 12:00 am
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Re: 750 Sport restoration project

Post by paso750 »

Well done! I reused mine after cleaning them up. I just applied a little of the mentioned ATE grease to prevent that they would instantly rust again. The condition of the piston is not so important. What is is that the rubber seal is in good nick and the cylinder wall in the cover is clean and smooth so it won't ruin the seal.
Nothing special to do before popping the piston out. You'll have to remove the cover from the bike as it'll have to be degreased and washed before and after polishing. Brake fluid is recommended to be changed every two years even if it's good longer than that. As yours is probably 3,5+ years old it's time anyway. Remove it from the bike. As you say it'll make working on it easier.
Rotate the pin of the piston while pressing on it and try to feel if it turns smooth or feels notchy in which case the piston should be rebuilt and greased. That'll require a new oil seal.

That rust is harmless as long as it's not so bad that the discs have rusted together. I'm not sure I'd remove that as then there would be blank metal which could rust even quicker.

This is one of my covers after some polishing with Autosol.
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Andrew2
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model: 750 Sport
year: 1988
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Re: 750 Sport restoration project

Post by Andrew2 »

Nice work there G. I did test the pin and it rotates quite smoothly so here's hoping it's just the seal which is definitely leaking some fluid out. Looks like the the seal is going to cost me $18 delivered from Gowanlochs. Can this seal be bought from any bearing shop or is it a special seal made specifically for Ducati?.

I turned the motor over by hand today and it moved freely enough and temporarily fitted the drive chain. I'm getting really excited again to get this running in the next week or two barring any major problems. It's good to get some enthusiasm back for her.
I can't imagine what she would look like by now if I hadn't rescued her :,(

I might leave the clutch plates in then and see if they work ok. It's an easy enough job to take them out later if need be.
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paso750
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Re: 750 Sport restoration project

Post by paso750 »

Good question. According to the picture of the seal on the Stein Dinse website there's a number under the lip. I'll check if I still have one right now. If so I'll post the number here.

Since the clutch is open you could take the discs out just to have a look and to see if anything is sticking together.
Andrew2
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Re: 750 Sport restoration project

Post by Andrew2 »

I just realised I posted the wrong photo above, here's the photo after it moved.
Image
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paso750
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Re: 750 Sport restoration project

Post by paso750 »

I think that was the correct picture as one can see the rust line has moved up.

You could be lucky. I have a seal and although it's quite difficult to read it says NA150 26-20-4 and and bit farther away W which may not be directly related to the number. NA150 describes the shape of the seal. See pic below.

If a bearing shop doesn't have it or can't get it try a hydraulics shop. I'm certain there are alternative types that could be used as well.
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Andrew2
paso grand pooh-bah
Posts: 504
Joined: Thu Oct 27, 2011 7:47 am
model: 750 Sport
year: 1988
Location: Wollongong,Australia

Re: 750 Sport restoration project

Post by Andrew2 »

Not sure what's going on with my computer but it was showing the photo with the cylinder down and now it's as you say :wacko: . Weird, I've had a couple of problems since posting again. Maybe it's this new computer....or the Wild Turkey :beer: :lol:
Andrew2
paso grand pooh-bah
Posts: 504
Joined: Thu Oct 27, 2011 7:47 am
model: 750 Sport
year: 1988
Location: Wollongong,Australia

Re: 750 Sport restoration project

Post by Andrew2 »

Thanks for those numbers, I'll chase that up tomorrow. I might give Brad the bike boy a call tomorrow as I don't really like dealing with the current owners of Gowanloch motorcycles. I got my last belts off Brad, he's a cool bloke.
Andrew2
paso grand pooh-bah
Posts: 504
Joined: Thu Oct 27, 2011 7:47 am
model: 750 Sport
year: 1988
Location: Wollongong,Australia

Re: 750 Sport restoration project

Post by Andrew2 »

Having some trouble finding that seal. I rang Freudenberg here in Australia and nothing come up on their inventory with the number NA150-26-20-4. If I have to put the original type seal back in to get me by what would I be looking for, an oil seal with 26x20x4 dimensions?.
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