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 Post subject: 1990 750 Sport - possible project
PostPosted: Sun Oct 16, 2016 9:23 am 
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Joined: Mon May 13, 2013 2:57 pm
Posts: 32
Location: Norway
Just made an agreement with a shop owner to buy a 1989/90 750 Sport "project". The red/silver one.
The bike was limping into his shop some 10 years ago on one cylinder. I has run about 88.000 km.
The top and cylinders was taken off, and excessive wear was discovered on the cylinders and pistons. The owner didn't want to throw money on it, and the shop owner bought it as a private project. 10 years down the road, nothing has happened and I have made a deal with him to buy it for about 600,-US$ / €550,-.

My question... should I look for å couple of SS/Paso/Elephant/+? piston&cylinders and just cross my fingers that the rest of the engine is OK, or must I do a full engine dismantle since it has 88' on the meter?
Are the cylinders and piston shot because of normal life span, or does it point towards a bad oil pump etc?

Any experience with tossing the Weber and find a couple of Mikunis from the 91-97 900SS?

I'm not sure if I should restore the bike or just part it out as parts&money for my F1 project.

No pictures at the moment since i'm going to pick it up during next week.


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 Post subject: Re: 1990 750 Sport - possible project
PostPosted: Sun Oct 23, 2016 2:52 pm 
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Joined: Mon May 13, 2013 2:57 pm
Posts: 32
Location: Norway
Have picked up the bike and the different pieces. Looks complete and nice except from the front cylinder. There is a ridge on top of the cylinder. The piston looks OK but it has some miscolor from what I think is the exhaust blowing past the piston rings because of the wear.

Is it OK to get a new(used) front cylinder and new piston rings, and re-use the piston?
Will of course check to see it its within tolerance, but if that is OK i guess i don't need to change it?
The wear on the front cylinder, is this because of lubrication problems etc I can/should fix, or just bad luck...?

Are the front cylinder on the 750 sport and Paso unique, or can I use any 88mm cylinder from 91- ? SS/Monster etc?

The engine serial number is very low (7500083) so i guess this is a 1988 model. It's sold/registered in 1990 here in Norway.

Anyone have a front cylinder laying under the bench we can do a deal on?

Thankful for any advice and help.


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File comment: Cylinder & piston
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File comment: Piston
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File comment: Cylinder ridge 2
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File comment: Cylinder ridge
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 Post subject: Re: 1990 750 Sport - possible project
PostPosted: Mon Oct 24, 2016 11:23 pm 
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Joined: Thu Oct 14, 2010 11:23 am
Posts: 1180
Hello Desmo22

Well, I will chime in.

Do not know where you live, but here in the USA a nice 750 Sport has trouble selling for $3500. Those at $2500 to $3000 do OK, but at $5000 or so there appears to be no takers. I have an 89 frame and NOS tank, and not sure what I will do with it since a complete project bike would easily cost $7500, and then I could get half of that at sale.

Those are simple air-cooled cylinders, instead of the oil/air versions found on many 750 Sports---like most in the US. They are same as the F1 and the Paso, other 750 Sports, and maybe some very-early 750SS engines---up to 1992 or so. Later versions have different locations for the oil passage dowel, the oil rings, and different locations for the cam belt pulleys. Ian Gowonloch (Italspares), in OZ, still has NOS sets of what you need, and he puts them on ebay when he feels like it. Rings for all the 88mm 750 pistons seem to be the same, and are found at your Ducati dealer and on eBay. Your pistons may, or may not be, after-market, since they seem to have some slight compression bumps on them. Hard to tell.

There are honing brushes (I like the ones that look like pom poms) that can be found close enough to 88m to work just fine.

Without taking your engine apart it is hard to tell if doing it part-way will be OK.

Hopes this helps some.

MikeV

Your rear cylinder is not identical to the F1, since those have the notch for the exhaust in front. But the H cylinder is. Some sets have two notches on the V cylinder to fit several engines.


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