Hi-Comps ready to drop

[jklnhyde]

I might drop the hi-comp pistons in the Paso as long as I don't have to battle too many variables along the way. I have the plastic all off to replace a dead fuel pump, so I might as well do somthing else while there. Besides replacing the timing belts and adjusting valve clearances, and head, valvetrain and base gaskets, what else should I budget for.
Yes, budget; the CBX stopped firing and the Enfield stopped carbureting. I'm low on cash; I want the Ducati to be done fast and on the cheap. Hit me!

Rick

[jklnhyde]

Arrrgh!!!! The dissassembly went without a hitch, but, SURPRISE!!, I think the previous owner had already put hi-comp pistons in! The pistons I pulled out are identical to the hi-comps I ordered, and even have the same markings underneath: 09 3528.
Can this be possible?

Rick

[paso750]

what compression ratio are they ? The Paso 750 is already higher compressed (10:1) than ie a 750 Supersport or Monster (9:1).

G.

[jklnhyde]

Not sure of the compression, but the dome on the new hi-comp pistons is much bigger than on stock pistons I've seen. (Ebay has a couple of photos of stock and hi-comp pistons for comparison)
At this point I'd love to bore out the cylinders and go with some 90mm pistons, but can't justify the expense, so I'm going to have to put it back together as is. What's a good place to get the gaskets and seals?

[jcslocum]

Try Ducshop in Atlanta or maybe Ferracci in Philly.

[jklnhyde]

Yeah, waiting on replies from one other source. So far three other sources have been no-go for the parts I need. As for the cam pulley tool, anywhere I can find it for less than the $80 most places want for it?

Rick

[paso750]

maybe worth a try


two on ebay
http://www.ebay.com/itm/DUCATI-CAMBELT- ... 3cbd64cfd7
http://www.ebay.com/itm/DUCATI-BELT-LAY ... 20bdf77b88

G.

[Mc tool]

Arrrgh!!!! The dissassembly went without a hitch, but, SURPRISE!!, I think the previous owner had already put hi-comp pistons in! The pistons I pulled out are identical to the hi-comps I ordered, and even have the same markings underneath: 09 3528.
Can this be possible?

Rick

yeah ! been there done that , I bought a set of 94mm pistons and when I pulled her to bits I found some bastard had already done it. I am real pleased that I didn't send the pots off to be bored and replated ( that was the plan ) I spose they will wind up in the paso

[jcslocum]

Call Commonwealth Ducati in Kentucky and ask for Aldrin. Tell him Jon from DESMO told you to call. I'm sure he can help you.

[jklnhyde]

Thanx for the tips, fellas'!! I'll report back...

[paso750]

I'm a bit confused.
The Paso 750 manual claims a CR of 10:1; is this correct? At several sites I've seen specs as low as 9.3:1 for the Paso 750/ F1 750, and 9.5:1 for the 750SS of the same years. If the posts on this site are correct, then the Paso/F1 have the higher (10:1) CR and the SS/M, lower CR. Ok, I got it. So, are the two identical sets of domed pistons sitting on my bench the stock (higher CR) Paso/F1 pistons or are they higher (than normal) CR for the Paso/F1...how do I tell them apart? One set was already in the motor, the other I bought as "high-compression Paso 750 pistons". Did they mean 'higher-than-stock compression, or were they identified as "yes, they are high compression pistons, beacuse they came from the Paso/F1, sir."

Input please

The Paso manual is correct as you can see also in several magazines or books. According to the original workshop manuals the 750SS was 9:1, the 900SS 9,2:1. There is no 750SS the same year as the 750 Paso only the 750S which had the identical engine.
I had to go through my parts boxes today as I was looking for something (which of course I couldn`t find) so at least I dug up the original pistons (which again were in the last box I checked).
I`m afraid you replied to yourself as the answer seems to be the last one. My bike was stock before it was converted to 780cc.
Here some pictures:





these are original 750SS/Monster pistons:


The original Paso pistons can not be bought from Ducati anymore.

G.

[paso750]

I put mine away so I can´t measure them but here`re some HC piston that are also for the Paso. Maybe the measurements help you to identify.
http://www.kaemna.de/cms_de/katalog.htm ... tikel=2572

G.

[jklnhyde]

Well, I got a hold of the seller and explained to him the issue of Paso stock, high-comp pistons vs. aftermarket stock bore higher-comp pistons. He came back saying Paso's came with flat topped pistons as stock, with a 9:1 CR, and aftermarkets for it are domed with 10.5:1 CR. This is coming from a well known Guzzi/Ducati parts vendor/racer etc.

Should I just live with no definate answer to this question? I buttoned up the engine already, but dont know how to archive the leftover pistons, stock or aftermarket...ha,ha!

Rick

[paso750]

He`s wrong. Let him look at the parts catalogues or the specs of the F1, let him check what`s offered used
http://www.ebay.de/itm/Ducati-F1-750-Bi ... 0868879995
http://www.ebay.com/itm/Ducati-88mm-Pis ... 3f0ff6e084
and have him google the part number:
http://www.loudbikestore.com/067047400- ... 14099.html

Aftermarket hi comp pistons are usually in the range of 10,8:1 - 12:1.

G.

[paso750]

Btw one of the Paso brochures shows an image of an open cut engine and you see the pistons there, too.