750 sport dropped the primary drive sprocket

[mickyfinn]

Took the old girl (750 sport) out for a spin today with my young nephew on the back, got 200m up the road when the bike lost drive from the main drive shaft, found the front sprocket (see photo attached) on the road about 50m away but nothing else, the sprocket looks okay, the splines dont seem to extend all the way from the front to the back, seems to be missing about 10mm of splines from the outer part of the sprocket, the splines closest to the engine look okay. There is a threaded hole in the middle of the drive shaft, its dirty and does'nt look like its had a screw in there for a while.

My question is this, does anyone have a photo of the front drive sprocket in situ so that i can tell what mine is supposed to look like, my parts manual seems to have 2 types of sprockets, none of which look like mine.
Secondly is there is supposed to be some sort of plate on the end of the drive shaft to hold the sprocket in place, if so i wonder if i could just make one up out of a heavy washer with a new bolt ?

Thanks in advance

Mick

[Mc tool]

Looks to me like the retaining ring is knackered .... lost its splines , and the whole plot just fell of the end of the shaft ..... AND you have the same kitchen bench top as me

The retaining ring ( different to yours as this is a 906 and the sprocket is on the other way round ) should have splines in its center which locate in a groove round the end of the shaft . When the retainer ring is fitted you slip it on to the shaft and then rotate it ( 1/2 a spline ) slightly in the groove and fit the cap screws , this stops the sprocket falling off . In your case there is no bolt fitted to the hole in the end of the shaft

[paso750]

this is your setup

I hope you still have that washer behind the sprocket as according to the parts catalogue it comes in three different sizes.

G.

[mickyfinn]

No Paso 750 i could'nt find part no 14 and as for part no 31 mine is round rather than oval, but how hard can it be to find a washer that size ?

[paso750]

that washer is od 36mm, id 25,3mm, thickness 0,8 or 1 or 1,2mm.
The question is what is that washer for and what defines the necessary thickness ?

[mickyfinn]

Many Thanks Hamish and Paso 750, you were spot on Hamish, i have stripped the outer ring, wow thats one to check on your bikes guys, never thought that might happen. Guess i'll have to buy the sprocket and ring as they probably come as a pair, as for the washer maybe its set into the engine casing rather than floating free on the shaft, if i have lost it i should be able to buy all 3 you mentioned Paso 750 from the bolt shop and try them all till i find the one that fits.

[907pasonut]

my 907 doesn't have that washer (14) and I can't think what it could be for, as the sprocket retainer (31) keeps the sprocket in place...
...Mc Tool showing off his new nylon swinarm protector...probabily the last one on planet earth

[Mc tool]

No , I have another still in the packet .
I cant figure out what that washer does either , unless the 750s sprocket is only 1/4 inch thick in which case that washer might act as a packer so that the sprocket doesn't wiggle about to much on the shaft , the paso sprocket being 1/2 inch odd thick ( with that extra shoulder width ) would be less wiggly.... maybe

[mickyfinn]

I'm beginning to think that the schematic might be a bit misleading, i cant see any need for a washer there either, it also doesnt show the bearing and seal that sits in the gearbox housing behind the sprocket, maybe the washer in the schematic is actualy inside the gearbox behind the bearing and seal ?.

As for the retaining ring i have contacted a machine shop that do a lot of work on sidecar racers, they say they can use my old retaining ring and weld a sleeve inside it enabling me to bolt the sprocket on to the end of the driveshaft using the existing unused bolt hole. The schematic in the parts catalogue shows a similar set up see items 16 17 and 18.

Anyone want to jump in here and give me some for's or againsts please feel free !! i dont want the chain flying off at 120kmh

Mick

[paso750]

I agree some schematics can be misleading but in this case I doubt it because the washer that`s on the inner side on the drive shaft is shown in the parts catalogue as well. It might be this one sits on the outer side behind the oil seal but why would it come in different thicknesses of 2mm increments ?!
That shim is shown in all parts catalogues from P750, 906, 907ie etc.
I guess the easiest would be to ask a Ducati mechanic. Someone who rebuilds Duc engines will know.

As for the retaining ring I would just get a new one and that`s it. Why instantly check for modifications. The retaining ring should be changed every time the sprocket is but it`s often not done.

G.

[Mc tool]

Yeah mickyfinn , save yourself a whole bunch of fucking about and just get a new one (or two , never hurts to have a spare ) , probly not that expensive and as they are similar across the range Id be surprized if it wasn't in stock. My 906 sure as heck has never had such a washer in the time I have owned it and my sprocket didn't fall off , I fell off but I don't think it was a lack of sprocket washer that caused it .. Good times

[mickyfinn]

Thanks Guys, our local dealer does'nt stock any parts pre 1990, any ideas where i might get one from, i'm waiting on a reply back fro Des Stein

[paso750]

As far as I understand now (from the Haynes manual) that shim is still inside the engine case and with the one which is on the other end of the gearbox makes sure the gearbox sits centered. So it`s not relevant in this case. Sorry if I caused any confusion with that.

Tell your local dealer he`s an idiot if he doesn`t know that that sprocket retainer clip is used on almost every Duc from the 90s.

Ducati 600 SS `95/97
Ducati 748 SP, Biposto
Ducati 750 Paso `84-`92 , BJ 1984 - 1992
Ducati 750 Sport
Ducati 750 SS `91
Ducati 750 SS `92
Ducati 750 F1/Laguna Seca
Ducati 851 Superbike Racing `91
Ducati 851 `90 SP
Ducati 851 `91-`92
Ducati 888 Superbike `92
Ducati 900 SS `90
Ducati 900 SS F.E. `98
Ducati 900 SS/SL `94-`97
Ducati 906 Paso `88
Ducati 907 I.E. `92
Ducati 916 `94
Ducati 916 Monop.-Senna `95-
Ducati 916 SP `96
Ducati 916 `98
Ducati Monster 600 `94
Ducati Monster 600 `98 Dark
Ducati Monster 900 `93
Ducati Monster 900 `94
Ducati ST 2 `97

The part number is 067016105 or now 82610111A.
Never go to a Duc dealer and say you`re looking for parts for an old Duc. Always ask them if they have or can get a certain partnumber. They just need to type that in their computer to check availability w/o having to go through parts catalogues and lose time for something they won`t make any money with. Unfortunately that`s how it is.

[mickyfinn]

Thanks for that G, i did tell them it was for an 88 and they treated me like i was some sort of poor cousin. I'll have another go ! Thanks for the clarification on that washer, i was starting to get worried imagining the sprocket chewing out the engine casing.

Ha ha Hamish was more likely an excess of Steinlager that made you fall off !

[paso750]

if they don`t have it try Gowanlochs
http://ducati-gowanloch.com/catalog/fro ... ?cPath=479