ducatipaso.org

Please help!@!!!
i just bought a 1990 750 paso . been stored for approx 12 years. Started it up and it has severe bigend rattle. has compresion
both pots. I dont know full history , by the noise i suspect rear bigend - piston . Is this normal with this model ? do they have bigend trouble ? . The guy i bought it of said that it was ok when running last many years ago .Other than that it is not to bad for its age. When i bought it i was not expecting to do a complete rebuilt !! looks lijke i will have no chioce. Any advice would be most welcome. Kind regards Roy

Hi Roy,

if it was stored for 12 years did you just fire it up as it was ? If so that could be the reason.
If the engine wasn`t turned over or started once in a while the cylinder walls can become bone dry and there`s the posibility that the piston rings stick to them.
One should do a full service (incl. belts!), squirt a little oil in the cylinders and turn the engine over by hand a few times before trying to start it.
It`s hard to say what it is. I personally didn`t hear of bigend troubles yet. (unless problems with exhaust valves) The engines are quite robust if regularly serviced.
Cylinders and pistons are discontinued and chances to find new ones are rather low. Also used ones don`t appear so often, but there`re some guys who are parting out their bikes.
I guess you won`t have another option then starting with pulling off the head.

G.

been stored for approx 12 years. Started it up and it has severe bigend rattle. has compresion

I think the first thing I would do is put a tablespoon of kerosene(or sea foam-http://www.seafoamsales.com/how-to-use- ... tment.html) in each plug hole and turn the engine over by hand a few times with the plugs out, let it sit for a day or two then flush it out gently with air,use a rag to keep it out of your face In the mean time take the clutch apart and clean it up and check the plates for warpage. Take out the oil screen and clean it.Flush out the oil coolers.
change out all the fluids,belts, filters and plugs. After going over the bike generally for wear and tear. Let it idle till warmed up completely and try it out again. Spun bearings are not unheard of but most often are due to to a lack of maintainance.

Welcome,where are you located?

Are you sure you are not mistaking the trademark rattling clutch with loose big end?
All the suggestions above are solid, and stand for any motor stored for a long period of time.

Cheers,

Hi guys thanks for your in formation. I did spend a bit of time on the bike before starting it new oil , lube in the pots and turned it over many times be fore i started it. I tried to pull in the clutch lever while it was running it did not stop the rattle. I check both sets of valves all ok both cylinders have compression about 70 psi each. I think as you suggested i will remove heads and start from there. I am in Australia i was not aware that parst are so hard to get

G - Can I assume that a good piston manufacturer (Wiseco, Mahle) can produce Paso pistons? They may need the old one to see the basic shape, and the clearances should be readily available. I would think that a piston is a relatively straightforward item to produce.

For the cylinder, ditto for LA Sleeve or comparable for new plating? Possible/advisable to install a cast iron sleeve?

That`s a good question. I don`t know if these manufacturers have all the measurements to manufacture Paso pistons. One would have to ask.

Paso Engines are VERY VERY VERY close to the M750-SS750 engines.

the MAIN difference is in the CRACKSHAFT, the Clutch and some parts of the Gearbox and of course the heads where the Paso has big valves and the M750-SS750 has smaller valves.

Pistons are more or less the same,and any OEM or aftermarket (wiseco/ferracci/pistal) piston for SS or Moster 750 will fit the Paso 750.

I have an Old Elefant 750 engine dated around 1987-898 which was extremely similar to the PASO engine and which I modified adding:

- Paso Heads with BIG Valves.

- M620 Conrods (they were new and EXACTLY the same as the Paso750)

- Paso Primary gears with straight teeth (original engine had helicoidal teeth)

- Secondary Gearbox shaft of the M600 (its longer and allows to have the sprocket "outwards"

- a Mix of gears coming from different engines in order to have a "close ratio" Gearbox.

- Ferracci pistons 13.1 slightly machined to match my superhot NCR camshafts.

- Ferracci flywheel

- adjustable cam-gears for MODERN cambelt profile (round teeth)

- FCR39 carbs & ignitech programmable ignition.

Most of the parts had either polishing or shotpeening treatments.

As for the Cylinders, once you get the pistons the re are companies out there that will RE-CHROME and machine them tu suit perfectly the new pistons; i had mine done in Italy (same company that does them for BMW and Ducati) , but there are many others that provide the same service worldwide.

Last , There is a Chap in Autralia who can , for sure, fix your bike, you can reach him through his website http://www.bikeboy.org

Hope this helps.

Damondarwin's user name seems to suggest that he is in Darwin (in the Northern Territory). If this is the case he is about 3700 km from Bikeboy's shop! Having said that, I have heard that Bikeboy is very good.

Mike

PasoRoo wrote:Damondarwin's user name seems to suggest that he is in Darwin (in the Northern Territory). If this is the case he is about 3700 km from Bikeboy's shop! Having said that, I have heard that Bikeboy is very good.
Mike

It is still duable.

I purchased my (half) engine in Genova (North Italy) sent it via courier to Lecce (South of Italy) got it done sorucing the parts all over the world (btw, the NCR camshafts come from a fellow Pasoista in USA...) and then once it was finished I got it shipped to the UK where I live to be then fitted to a special SS I am building.

The engine is approx 65 kgs so is not a big parcel...

Pistons are more or less the same,and any OEM or aftermarket (wiseco/ferracci/pistal) piston for SS or Moster 750 will fit the Paso 750.

Here I would have to disagree. They do have the same 88mm diameter but they are not the same. The compression ratio is higher.
What`s the difference in the crankshafts ?

G.

paso750 wrote:

Pistons are more or less the same,and any OEM or aftermarket (wiseco/ferracci/pistal) piston for SS or Moster 750 will fit the Paso 750.

Here I would have to disagree. They do have the same 88mm diameter but they are not the same. The compression ratio is higher.


G.

Ah , so they are better

Damondarwin wrote:Please help!@!!!
i just bought a 1990 750 paso . been stored for approx 12 years. Started it up and it has severe bigend rattle. The guy i bought it of said that it was ok when running last many years ago.

No way was it running properly when it was laid up! Guy has either forgotten about failure or purchased it as non runner. Brief lack of oil might be hard on cams but oil to mains etc is there in less than a second.

Hi mate i agree with you he would have known. I will; give credit to him when i contacted him to discuss my concerns that the motor was ( stuffed, ) and that i was not HAPPY , he refunded an amount that would assist me to complete a rebuild.

I am slowley pulling it apart , I have forgoten the lack of Quality that is apart of owning a Ducati. The last one was a 1974. 450 single desmo, and that was a vaibriating dog. So thirty years on i thought i will try again, with aim to restore and ride on rallies

Thanks for your reply

Hi mate i agree with you he would have known. I will; give credit to him when i contacted him to discuss my concerns that the motor was ( stuffed, ) and that i was not HAPPY , he refunded an amount that would assist me to complete a rebuild.

Brief lack of oil might be hard on cams but oil to mains etc is there in less than a second.

To be fair, in twelve years a lot of things can go wrong in any engine even if it has been properly sealed for such a long storage. It takes less than a second to wipe a dry bearing or a dry cylinder bore on startup even in a recently assembled engine then alone one that sat for twelve years.