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 Post subject: Two steps forward, one step back, lather, rinse, repeat
PostPosted: Tue Jun 20, 2017 3:15 pm 
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paso grand pooh-bah
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Joined: Wed Jan 19, 2005 12:00 am
Posts: 691
Location: CNY, US
model: 750 Paso
year: 1988
In the never-ending quest of returning my Paso to road duty, I've made some advances, only to find the the next stumbling block. My latest tribulations:

The original problem this year, was the clutch slave/cover. After getting my original cover sleeved with a steel sleeve (to fix the piston bore, which got 'widened' when a bearing grenaded and the piston itself went orbital in the bore), it turned out that some cracks were introduced in the fluid veins in the case. Instead of fixing it, I found a relatively new one, which also had the over-engineered piston (with two bearings). I opted to rebuild and use this piston instead of the original, with the single bearing and mushroom pin. Bled the clutch up, fired the bike up and before I even went 50m ... realized the chain was exceptionally loose.

Loosened the axle eccentrics to adjust the chain - looks like the chain has had it, alternating tight and loose. That wasn't the problem though: the problem was with the 8mm bolts that hold the brackets that hold the eccentrics. Brake-side, the lower bolt was really stuck. Once it finally broke free though, every time I'd turn it with the wrench - it would turn itself back a little. I've seen plenty of stuck bolts, but I've never seen a bolt that would try to screw itself back into its hole after you turned it. Long story short, at some point in the bike's past, that hole must've been stripped, and someone put a heli-coil in it, and now the heli-coil has failed. I wound up pulling the whole thing out.

So this is where I sit: new sprockets should arrive tomorrow, and hopefully my local shop can re-heli-coil this bolt hole. I suspect the same hole on the other side of the swing was similarly "fixed".

The upshot? I knew I'd had a 530 chain on the bike, but now I'm dialing it back to a 520 after reading through Ian Falloon's notes on Paso. I always thought the 530 was overkill, so I'm pleased about that. Provided I don't need to find a new swingarm or anything drastic. (If that's the case, I may just look into updating the bike to ride on 17" rims.)

Someday ...

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 Post subject: Re: Two steps forward, one step back, lather, rinse, repeat
PostPosted: Tue Jun 20, 2017 10:31 pm 
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Joined: Tue Jan 17, 2006 12:00 am
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Location: Lower Hutt, New Zealand
model: 750 Paso
year: 1986
Hey Faster,

If the helicoil route doesn't work there will be a spare swingarm somewhere. A 906 fits straight on. Replaced mine last year when the weld at the end of the swingarm split, where the escentrics fit. Those bolts are infamous.

Cheers,
Fraser.

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1980 Moto Morini 500 Sport
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 Post subject: Re: Two steps forward, one step back, lather, rinse, repeat
PostPosted: Wed Jun 21, 2017 12:00 am 
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paso grand pooh-bah
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Joined: Wed Dec 05, 2007 12:35 am
Posts: 1596
Location: Newzealand
model: 906 Paso
year: 1990
Mine needed work when I got the bike too . As Fraser says there will be a spare out there somewhere , and if not it can always be repaired ..... just depends on how much you want to spend . I have another swing arm here , is the worst of 2 I had and Im pretty sure its the same thing . Im not sure if people just over-tighten the bolts ( they don't need to be that tight ) or wether peeps just get them cross threaded because its sorta underneath and at a weird angle. I suspect the latter as all the ones I have seen damaged ( 4 in total ) have had damage to the start of the treads rather than be stripped full length....................or a bodged helicoil , probly the same deal as the original damage ..... tried to screw the tap in out of alignment ( shoulda took the swing arm off dummie :D ) and thus buggered right from the start

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 Post subject: Re: Two steps forward, one step back, lather, rinse, repeat
PostPosted: Wed Jun 21, 2017 5:19 pm 
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paso grand pooh-bah
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Location: CNY, US
model: 750 Paso
year: 1988
Good to know about the 906 swingarm; I see them come through on ebay relatively often. Hopefully I don' thave to go that route, but at least it's an option. It's also mildly reassuring that this is a common ailment. I'm still kind of surprised though; I bought the bike with 4k on it (15-16 years ago), and I never heli-coiled it - unless a shop did, and didn't tell me ...

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1988 Paso 750 #753965
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 Post subject: Re: Two steps forward, one step back, lather, rinse, repeat
PostPosted: Wed Jun 21, 2017 8:51 pm 
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Joined: Fri Jul 24, 2015 11:21 am
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Location: Belgium
model: 750 Paso
year: 1989
Hi, torque the 2 bolts (either side of the swingarm) with 20 nm (roughly 15 footh pounds).
Preferably dip the threads with a dot of (ceramic) grease before you torque them.
This will increase the lifetime of the threads (in particular alumnium will benefit from it).
However, if you use a lubricant reduce the torque with about 10/15%.

Frank

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 Post subject: Re: Two steps forward, one step back, lather, rinse, repeat
PostPosted: Wed Jun 21, 2017 10:45 pm 
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paso grand pooh-bah
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Joined: Wed Dec 05, 2007 12:35 am
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Location: Newzealand
model: 906 Paso
year: 1990
While we are talking swing arms its probly worth taking it out just to get a coat of fresh grease on the pivot bolt ..... assuming it hasn't already seized... and to regrease the bearings in there too
The big bush ( bottom centre ) is the inner race for the needle rollers on the left side , the pivot bolt can seize in this bush , and the one above it (with the two smaller spacers is the spacer assy for the rhs ball bearings which can do the same but not usually as bad. :)


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 Post subject: Re: Two steps forward, one step back, lather, rinse, repeat
PostPosted: Thu Jun 22, 2017 9:41 am 
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Joined: Fri Jul 24, 2015 11:21 am
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Location: Belgium
model: 750 Paso
year: 1989
To be honest, Ducati did use helicoils themselves (engine twice).
Possibly they overtorqued them during service (20 nm is not that much for an m10 bolt, also an alu swingarm were the exception in 1988).

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 Post subject: Re: Two steps forward, one step back, lather, rinse, repeat
PostPosted: Mon Jun 26, 2017 6:02 pm 
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paso grand pooh-bah
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Location: CNY, US
model: 750 Paso
year: 1988
Frank.61 wrote:
To be honest, Ducati did use helicoils themselves (engine twice).
Possibly they overtorqued them during service (20 nm is not that much for an m10 bolt, also an alu swingarm were the exception in 1988).


Well, that makes me feel better, I guess. I was kind of surprised that either the previous owner - who didn't use the bike all that much -
might've had it done, or a shop did it without telling me, since I've owned it. Either way, I'm not attempting that fix, so hopefully my favorite shop can make it right for me.

McTool - thanks for the pics & walk-through on the re-grease. That's not a bad idea at all. Mine was still pretty cooperative, but it certainly can't hurt.

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1988 Paso 750 #753965
1997 Monster 750


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 Post subject: Re: Two steps forward, one step back, lather, rinse, repeat
PostPosted: Mon Jun 26, 2017 8:42 pm 
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paso grand pooh-bah
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Location: Newzealand
model: 906 Paso
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:) I just remember what a shit of a job I had getting mine apart :) and I figure why wait till you need to get the swing arm out and then run into complications when you really :evil: don't :evil: effing well :evil: need it NOW :mad: :D :) :lol:

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