Author Topic: Aw, Rats. Swingarm BS  (Read 978 times)

Offline wymple

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Aw, Rats. Swingarm BS
« on: March 20, 2018, 03:09:16 PM »
My 1984 Cal II decided it no longer wants to downshift, and the problem is internal. So I set out to pull the trans off. One swingarm pin came right out, the other was seemingly welded. I broke a pair of real good Allen wrenches and never budged it. Que the torch, as I'm short on patience with this kind of stuff. I got it red hot just to break it loose, it still wouldn't unscrew. I got it rocking back & forth about 1/4 of a turn, and that took a half hour. PB blaster & all that crap. So I got out the air gun and worked it back& forth for awhile, gaining a little each minute. When it decide to come out, it took all the threads with it. Wonderful. Now I'll have tap it out to something bigger & have my son the machinist make me a new piece to screw in there. There may be a better way, but I don't care about originality, and that's the easiest thing to do.
« Last Edit: March 20, 2018, 03:10:18 PM by wymple »
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Offline fotoguzzi

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Re: Aw, Rats. Swingarm BS
« Reply #1 on: March 20, 2018, 03:18:28 PM »
Or get a new frame. Rust is evil!
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Offline rodekyll

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Re: Aw, Rats. Swingarm BS
« Reply #2 on: March 20, 2018, 03:42:30 PM »
I'd put your son, the machinist, in charge of the repair.  The only guy I ever saw successfully repair a Tonti pivot point was Bob Nolan, and he's not going to do yours.  He had two approaches, neither of which he really liked:  drilling out the stripped insert and welding in a new bung, and replacing that entire frame area with a wreck donor.  The alignment needs to be very precise or you can have a permanent misalignment of the drive shaft to the transmission output shaft. 

Offline wymple

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Re: Aw, Rats. Swingarm BS
« Reply #3 on: March 20, 2018, 08:40:39 PM »
The hole is still round, so alignment doesn't worry me much. If I retap it I can't picture getting .001 out of whack. And nothing was rusty, the damn thing just locked up tight on the threads. I've seen fine threads do the same thing on ball hitches. I'll see what we can do, we ain't skeered. :bike-037:
« Last Edit: March 20, 2018, 08:41:51 PM by wymple »
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Offline huub

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Re: Aw, Rats. Swingarm BS
« Reply #4 on: March 21, 2018, 05:57:35 AM »
oversized swingarm pins used to be available from guzzi , you might check if that is still the case.

Offline 5154guzzi

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Re: Aw, Rats. Swingarm BS
« Reply #5 on: March 21, 2018, 10:38:22 AM »
The 2004 and later Tonti frames use a larger diameter threaded pivot pin.

Offline wymple

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Re: Aw, Rats. Swingarm BS
« Reply #6 on: March 22, 2018, 12:14:12 AM »
That seems to me like a perfect fix.
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Offline tris

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Re: Aw, Rats. Swingarm BS
« Reply #7 on: March 22, 2018, 02:49:39 AM »
It strikes me that if your son has access to a big enough machine the simplest solution would be to throw the whole frame on so that you can line bore through both holes and fit the larger pins described by 5154

It will be very tricky to maintain the alignment from one side as RK suggests
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Offline wymple

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Re: Aw, Rats. Swingarm BS
« Reply #8 on: April 10, 2018, 08:43:49 PM »
Oh, this is just great.  I pulled the trans apart and cannot spot a single thing wrong. Nothing broken, worn at all, everything looks like new. Now I'm in over my head as I know little to nothing about this, so it will have to go to the dealer and it's a busy time of the year for him. I'll probably have to ride the Suzuki to a Guzzi rally or two......  :cry:
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