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Old 01-06-2013, 05:01 PM   #1
JonnyCash OP
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caring for a Guzzi U-joint

Hi all. I will soon be putting the swing arm back on my T3 project bike, and I am thinking about what to do with the U-joint. I have replaced the carrier bearing in the swing arm and the old u-joint seems to be in fine shape.No play, and everything moves smoothly and quietly. I find it interesting that these double u-joints seem to be a source of trouble on these bikes, whereas on BMWs, they are very reliable. To look at it though, the guzzi system is much beefier, and the BMWs is puny. The one thing I can see in BMW's favor is that it is bathed in gear oil. On my /5 with an R100s motor, replacing the shaft oil is the only thing I've ever done, as far as maintenance is concerned in the 19 yrs I've owned it. I'm sure they do fail, but I've never heard of it.

So I'm about to put it together, and feeling like I should do something to it besides just throw it together. I've considered taking it apart to grease it(no zero fittings like on loops), or soaking it in gear oil for awhile before assembling. I've also thought about putting some oil in the boot before sealing it up. Part of me wants to just replace the joints while I'm in here, but MG cycle wants like $130 for the pair, which seems like too much to spend if I don't really need it. I did find a guy on ebay selling what I would assume are chinese ones for like $20 apiece, but I'm not willing to chance that.

I keep finding pictures online of u-joint disasters on these bikes. When I see these, I can't help but thinking that the owner had been ignoring some increasingly bad noises to get to that point. I consider myself to be quite mechanically compassionate, and sometimes paranoid about hearing phantom noises when riding, so I don't imagine myself having anything like that happening to me. But I don't want to set myself up for it either.

It's funny, when I got my BMW, I was 21, and super broke. I got it as a non running abandoned project with electrical problems, and knew nothing about motorcycles. I was working as a car mechanic at the time, so it wasn't hard to figure things out, but everthing on the bike was new to me. I just went through the wiring, and made it all right, hoped for the best and just rode the damned thing, didn't worry at all. Sure I had some problems, but who cares? Now 19 years later, I've done a lot of this stuff, and while not loaded, I can afford to do things right and have ten times the tools I had then............and I worry like hell over every last thing. Being 21 was great! Being 40 isn't bad either, but I'd choose 21 over it.

Anyway, anyone have insight on this subject? Thanks

Mike
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Old 01-06-2013, 06:19 PM   #2
F_Sahms
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Guzzi u-joints last a good long time without trouble. What's the service life of an airhead u-joint?

But Guzzisti can be frugal, and qualified service has rarely been available all over. They usually give fair warning.

I've soaked em in gear lube, and used a needle grease gun to squirt some under the seals. It probably doesn't matter.

How's the old u-joint fit in the new carrier bearing? Sometimes they are loose and spin. I have center-punched the OD to get an interference fit, and some people use lock-tite.
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Old 01-06-2013, 06:37 PM   #3
MZRider
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Quote:
Originally Posted by F_Sahms View Post
Guzzi u-joints last a good long time without trouble.
102k miles on the u-joint in my '69 Ambassador.
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Old 01-07-2013, 03:15 AM   #4
Morizzi
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Mike,

to try and answer your question rather than try and uphold Guzzis honour.

There is a number of things in no particular logical order.

1. A T3 doesn't have the extra o-ring and washer on the output shaft. It will leak a bit of oil between the shaft and worm drive ring that will help to lubricate. The extra o-ring came in the mid 80's. The LM IV was the first, I think.

2. Keep your carbs well balanced and idle above 1000rpm. Unlike the BMW the Guzzi timing isn't even. This helps to minimise the pulses the joint receives. Helps the clutch too.

3. Make sure the cush drive rubbers are compliant. Some remove half of them but I don't. I prefer to drill a hole or three in them to give them the 'give.'

4. Make sure none of the caps are rotating in the yokes. A bit of retaining fluid can help.

5. I tend to spray the joint with Tectyl 506. Just a waxy coating that helps to protect and seal.

6. It can be tricky removing the cross and returning it without damage. If you are really concerned then try squirting some grease under the seal. I personally wouldn't soak it in oil as you are more likely to wash out the grease. The oil will be short lived.

7. There is no seal between the swing arm and rear drive on that model. Oil will travel up from the drive too. That's how the rear drive vents as there is no pressure valve.

8. The centre yoke acts like a short shaft so swing arm alignment isn't super critical but I centre the arm by counting the threads on the pivot pins. Anything you can do to align the output shaft and drive shaft will help.

Cheers

Rod
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Old 01-07-2013, 04:42 AM   #5
mtiberio
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you will feel vibration in the right footpeg before they fail. I had one fail while 1000 miles from home. I rode it home, and when I pulled the swingarm, the ujoint fell on the ground in 2 pieces. I also raced for many years with no failures.
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Old 01-07-2013, 07:01 AM   #6
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John Swartz, long time SoCal dealer and MGNOC Officer, offered this advice.

When I replaced the swingarm boot, lubed its bearings, he said put about 2oz of gear oil in the swingarm.

The heating and cooling cycles will pull the oil into the u-joint.

Over 60k miles, much of it two-up with heavy loads, never an issue on the old SP1000.
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Old 01-07-2013, 07:09 AM   #7
sjc56
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Or some olive oil.
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Old 01-07-2013, 09:52 AM   #8
JonnyCash OP
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Quote:
Originally Posted by F_Sahms View Post
Guzzi u-joints last a good long time without trouble. What's the service life of an airhead u-joint?

But Guzzisti can be frugal, and qualified service has rarely been available all over. They usually give fair warning.

I've soaked em in gear lube, and used a needle grease gun to squirt some under the seals. It probably doesn't matter.

How's the old u-joint fit in the new carrier bearing? Sometimes they are loose and spin. I have center-punched the OD to get an interference fit, and some people use lock-tite.
Service life? No idea, as I've never heard of one going bad, ever. I'm sure someone has used one up, but I've never heard of it.

The u-joint that was in this bike was totally sloppy in the carrier bearing. The bearing still spun very smoothly, and the crosses in the u-joint were still fine, but the fit of the joint in the bearing was very sloppy. This bike, though a T3, has the rear end out of an 850T with a drum brake. I still have the swingarm and driveshaft out of the parts T3 (where your trans came from). The joint was good all around on this one, but then I realized that the carrier bearing from the disk swingarm is bigger than the one in the drum rear end. So now I'm putting the swing arm, and u-joint from the parts bike on the project bike. It is at the soda blaster's shop right now, when I get it back, I have to TIG on a tang for the brake stay arm needed for the drum brake, no big deal.

Thanks everyone else for your suggestions, I think I'll put some oil in the boot before closing it up for good luck. Not olive oil though.
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Old 01-07-2013, 10:12 AM   #9
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So are you going to use the drum-style rear drive (with the little sump) or the disc type that came on the T3? I ask because the swingarms are different lengths to accomodate the slightly longer pinion carrier that goes with the disc-stype rear drive. You can't just bolt the drum-style rear drive to a disc style swingarm. The axle won't line up.
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Old 01-07-2013, 10:50 AM   #10
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You know, I put them side by each to see if there were any differences, and nothing jumped out at me, but it sounds like I'd better take a closer look when I get the swingarm back. Yes, I was planning to put the drum brake final drive on the disk swing arm, it's the only one I have. Shit! If it is indeed different, I'm going to have to get another u-joint, because the one that I have that went with the drum swing arm is chowdered up pretty badly where it slips into the carrier bearing. Thanks for the warning.
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Old 01-07-2013, 12:04 PM   #11
Rathlindri
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Quote:
Originally Posted by JonnyCash View Post

Being 21 was great! Being 40 isn't bad either, but I'd choose 21 over it.

Mike
Wait 'til you get to 58!!!
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Old 01-07-2013, 12:10 PM   #12
F_Sahms
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Quote:
Originally Posted by JonnyCash View Post
You know, I put them side by each to see if there were any differences, and nothing jumped out at me, but it sounds like I'd better take a closer look when I get the swingarm back. Yes, I was planning to put the drum brake final drive on the disk swing arm, it's the only one I have. Shit! If it is indeed different, I'm going to have to get another u-joint, because the one that I have that went with the drum swing arm is chowdered up pretty badly where it slips into the carrier bearing. Thanks for the warning.
The difference is a couple of mm, IIRC. Do you not have a disc type rear drive?

Does the bike have a drum or disc on the back?

I have seen folks use a shim of the correct thickness to allow the drum-type rear drive to work on a disc-brake swingarm.
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Old 01-07-2013, 06:59 PM   #13
JonnyCash OP
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The bike has a drum brake, with a cush drive, which I understand means it must be from an 850T, or 750S. I do not have a disk brake bevel box. The parts bike was missing tons of stuff, which is why I chose not to build it up. I do though have the pinion and its carrier from the parts bike(disk). Tonight out in the shop, I compared it to the drum brake pinion carrier, and as you said, the disk brake pinion carrier is considerably thicker than the drum brake version. I'm going to look into making up a shim to make up the difference, unless someone here wants to trade a good drum brake u-joint for the good disk brake u-joint that I have. Thanks for straightening me out here.
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Old 01-08-2013, 04:39 AM   #14
mtiberio
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you need a 2mm (or .080") spacer to fit the early drum rear drive to the newer disc swingarm...
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Old 01-08-2013, 05:16 AM   #15
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I may have a usable drum-sized U-joint in my pile of 850T bits. Lemme check tonight.
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