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 Post subject: Cog gear
PostPosted: Wed Oct 14, 2020 12:59 am 
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Joined: Sun Oct 06, 2019 1:28 am
Posts: 1
Location: USA
model: 750 Paso
year: 1986
I have replaced the sprag gear .bike started and ran ,for a little while ,then same problem again , would not start ,turns out cog gear is issue , removed and cleaned sanded with 1200 and replaced, now it will start , my question is how do I replace shaft that the cog gear is on ? , does it come out ? Any advice is welcome and greatly appreciated


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 Post subject: Re: Cog gear
PostPosted: Wed Oct 14, 2020 10:17 am 
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paso grand pooh-bah
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Joined: Thu Nov 03, 2011 10:13 am
Posts: 749
Location: Scotland
model: 907 I.E.
year: 1994
I presume you mean the starter intermediate gear? As far as I know the shaft is an interference fit into the crankcase half although I can't find any reference to replacing it in any Ducati workshop manual. Short of dismantling the engine you should be able to use a length of tube and suitable washers with a screw into the shaft to pull it out. You'd be best to heat the crankcase it the area of the shaft with a heat gun before pulling it .

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 Post subject: Re: Cog gear
PostPosted: Wed Oct 14, 2020 10:58 am 
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Joined: Thu Nov 29, 2007 2:38 am
Posts: 322
Location: UK
model: 907 I.E.
year: 1990
on the spare parts catalogue the gear is held with a circlip and the gear pin is bolted to the crankcase trough a long allen bolt.

my guess is that the pin is fitted with a slight interferance, and the bolt does the holding.


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 Post subject: Re: Cog gear
PostPosted: Thu Oct 15, 2020 9:11 am 
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paso grand pooh-bah
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Joined: Thu Nov 03, 2011 10:13 am
Posts: 749
Location: Scotland
model: 907 I.E.
year: 1994
angelix wrote:
on the spare parts catalogue the gear is held with a circlip and the gear pin is bolted to the crankcase trough a long allen bolt.

my guess is that the pin is fitted with a slight interferance, and the bolt does the holding.

Ah. That makes sense and explains the length of the bolt.

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1982 Pantah 500SL (now sold)


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 Post subject: Re: Cog gear
PostPosted: Thu Oct 15, 2020 3:19 pm 
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paso grand pooh-bah
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Joined: Tue Jul 29, 2008 9:50 pm
Posts: 3231
Location: Hilltown,Pennsylvania
model: 906 Paso
year: 1990
Sprag has to be the most troublesome part of these engines. I keep a supply of new springs and end up replacing them every other year. I have replaced the idle gear and shaft when experimenting with readily available springs I ended up welding the idle to the shaft during this trail. Yes the shaft is removable.In the end I found a guy in England sells the proper spring. I have also tried other types of sprags with no luck so far. Recently a new updated spag has become available From a source in Italy and I have one to try as once again it is slipping

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 Post subject: Re: Cog gear
PostPosted: Fri Oct 16, 2020 6:23 am 
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paso grand pooh-bah
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Joined: Wed Dec 05, 2007 12:35 am
Posts: 1760
Location: Newzealand
model: 906 Paso
year: 1990
Hi Higgy , do you think the sprag failures maybe oil type related. When I was still riding my Paso ( been near 15 years now ) I did about 60k kms on it and never had a sprag problem , did make some awful noises if it backfired when starting tho . I used valvoline xld oil . Just thinkin :-)

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 Post subject: Re: Cog gear
PostPosted: Fri Oct 16, 2020 3:34 pm 
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paso grand pooh-bah
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Joined: Tue Jul 29, 2008 9:50 pm
Posts: 3231
Location: Hilltown,Pennsylvania
model: 906 Paso
year: 1990
I think it is heat that sacks the spring so yes oil would have its part to play. Dont know if the st type oil slinger would help

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Ducati,making mechanics out of riders since 1946
There's no problem so bad that a little fixing can't make it worse! : )
If it ain't broke keep fixin it till it is
88 750
90 906
92 907ie


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 Post subject: Re: Cog gear
PostPosted: Fri Oct 16, 2020 8:58 pm 
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paso grand pooh-bah
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Joined: Wed Dec 05, 2007 12:35 am
Posts: 1760
Location: Newzealand
model: 906 Paso
year: 1990
I had a sprag "reverse" itself in an auto trans on my car (ZF 4hp22 ),pain in the arse as car wouldnt move off in drive , had to put it in L to move off then shift to D and then all was normal till next time I stopped .

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 Post subject: Re: Cog gear
PostPosted: Fri Nov 06, 2020 4:35 pm 
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Joined: Fri Jul 08, 2005 12:00 am
Posts: 327
Location: Winston-Salem, N.C. USA
model: 907 I.E.
year: 1992
higgy,
Surprised you have had to put so many sprag clutches in.
When I bought mine in 1992 it had 3,000 miles on it. I brought it home on a trailer, changed the oil and filter, wash and polished it, ready to ride. Push the starter button and the starter spun but didn't engage. Damn, brand new bike and I was ready to ride. I figure with new oil, everything was just more slippery. After research, took the side cover off and inspected the sprag clutch and spring was stretched and the blocks showed some flatting. Put a new sprag clutch in and it started fine. After 60,000 miles I am still on the same sprag clutch!
Seems the quartz clock takes a lot of electrical power. Most bikes would sit waiting for that weekend ride. You go to start the bike and the battery is low and this wears on the sprag clutch. It seems it doesn't get that full kick to engage as it does with a fully charged battery. After time and multiple "weak" starts it wears the sprag clutch. Some would use rubber washers and remount the clock to disable it keeping it from running the battery down.
I installed the Hicap battery cable kit and wow. The bike starts in their guaranteed one revolution. Really, what a difference, and my engine has been rebuilt, balanced, blueprinted,ported, the works and it takes more to spin it.
Just thought I would share this.
du907


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