T3 Rear Crank Seal

[Stu]

So I was warned by someone who works on these for a living that when putting an old Guzzi that's been standing for 30 years back into service I should expect to have to replace the rear crank seal sooner or later. Sure enough, on my first shakedown ride on the beast, there is oil peeing out of the hole in the bellhousing just above the drain plug. While this may or may not be the rear seal, I'm assuming it is and going in anyway... if it hasn't gone yet it sure as hell will; 44 year old rubber isn't going to last for ever.

Obviously, if I'm going to tackle this, it makes sense to replace any other ageing or wearing parts while I'm in there. It is NOT my intention to rebuild the engine and gearbox, both of which seem to be working well enough, but what other things should I be examining or replacing without question while I'm in there? Might as well do the job once and do it right.

Any hints or tips on how to go about it? I'm thinking I'll probably take the whole lump out rather than "crab" it. It'll give me a chance to give everything a good clean and easier access to any other stuff I want to have a look at.

Another thought, any special tools I'm going to need?

[Stevex]

Got a slight weep from that drain hole on my LM2. I know it's coming from the camshaft plug above the main seal.
atm it's not bad and I'm living with it.

[Kiwi_Roy]

I think they can also leak out in the camshaft area, I seem to recall someone saying to seal that with JBWeld
Either way it will involve removing the flywheel, I'm sure one of the experts will be by to verify that.
Stevex beat me to it.

[fotoguzzi]

It could be gear lube, smell it.. the clutch pushrod seals are a known leak spot and that would be gear lube not oil.
If you have a drop of oil the size of a nickel or dime on floor overnight you can probably ride another 40 years before worrying about changing the rear main seal.
I once fashioned a little diaper like mini pad to soak it up before getting around to fixing .

[Stu]

Yeah, thanks... it's not a slight weep or a few drops, it's pissing out! Pretty sure it's engine oil.

There's no leaving it the way it is.

[blackcat]

I'd measure the clutch plates as they maybe close to the end depending on mileage and you will need a clutch alignment tool or you can make one. I'd replace the transmission seal while you have it apart, and consider changing the original hub to the deep spline hub.

https://www.mgcycle.com/index.php?main_page=product_info&cPath=193&products_id=4766

[MotoG5]

When you get around to doing the work I have a used transmission input splined hub from my G5 that works great for doing clutch alignment on reassembly. If you dont come up with something else I would be happy to mail it to you. No charge and send it back when ever your done with it.

[Stu]

When you get around to doing the work I have a used transmission input splined hub from my G5 that works great for doing clutch alignment on reassembly. If you dont come up with something else I would be happy to mail it to you. No charge and send it back when ever your done with it.

I really appreciate that, but I'm in UK! Hopefully I can borrow something closer.

[acguzzi]

you might want to look at the alternator oil seal as well, and the gearbox input shaft oil seal.

[MotoG5]

I really appreciate that, but I'm in UK! Hopefully I can borrow something closer.

I checked to see your location but it was not listed so I just took a chance that you were not overseas. You should be able to run a used hub down. Quite a few were changed out on the G5s due to spline wear causing the clutch to hang up and not fully disengage. Good luck with your project, its a fair amount of work but very doable for the average home mechanic.   

[Stu]

I checked to see your location but it was not listed

Have added location to my profile (and an avatar of my old Ducati just to be contentious  )

[pehayes]

When you do this job:
1-replace rear main seal.
2-cover the edge of the cam plug with JBWeld.
3-put thread sealant on the bottom two bolts for the rear main carrier.
4-replace the gasket for the breather tube.

Are you sure it is engine oil?  Could be transmission fluid?  If the latter:
5-replace the transmission input seal.
6-replace the transmission input o-rings.
7-replace the throwout shaft cone seals (perhaps with the improved o-ring stack.

Patrick Hayes
Fremont CA

[Antietam Classic Cycle]

From "ThisOldTractor.com":


- Rear main seal.
- Rear main flange gasket.
- The two 12 mm aluminum crush washers that connect the small steel oil return line from the breather to the bottom of the bell housing.
- The gasket for the plate to which the large steel inlet line from the breather connects at the top right of the bell housing.
- Replace the 6 bolts that attach the flywheel to the harder 10.9 grade black oxide bolts; size: 8 mm × 1.25 mm × 25 mm.
- Replace the 3 metal strips under the 6 flywheel bolts with 6 Schnorr safety washers; size: 8 mm.
- Be sure to use a medium strength thread locking compound on the flywheel bolts and torque to 30 foot pounds.
- Be sure to use a sealant on the two bottom rear main flange securing bolts. These bolts go all the way through to the inside of the engine case and will leak oil if not sealed. I use a sealant such as ThreeBond 1184 semidrying liquid gasket.
- J-B WELD the cam plug. The cam plug is notorious for leaking oil. If I can see one, I fix it. I rough it up with a bit of sandpaper, clean it up well with carb cleaner, and then apply a nice thick coating of J-B WELD. Make sure to get a good coating of J-B WELD especially at the joint between the plug and the engine case.

And:

- Clutch shaft (input shaft) seal.
- Layshaft (output shaft) seal.
- On five speed transmissions, replace the single cover gasket if disturbed (MG# 14201110).
- On five speed transmissions, replace the O-ring that seals the pre-selector shaft (MG# 90706140).
- On five speed transmissions, replace both O-rings beneath the clutch input hub (MG# 90706203 and MG# 90706235).
- Replace the O-ring for the outer body of the throw-out bearing assembly (MG# 90706170).
- Replace the pushrod seals. Moto International sells a clutch pushrod seal kit MG# 14085900. It's a handful of small O-rings (5 or 6) that go down the hole in the input/clutch shaft to keep oil from leaking out the front of the shaft and into the clutch (MG# 12085901).
Note: Moto International is no longer in business, but I can supply the o-rings for FREE within the US, or for postage cost only elsewhere.

[Stu]

Thanks all, really appreciate the input. Will start on it at the weekend.

[rutgery]

If you've got access to a 3d printer I can send you a file to print a clutch alignment tool, you'll need a bolt and washer for the center to apply pressure to the clutch springs. Worked a treat on my Sport build when I installed the lightened flywheel.

[Stevex]

While you're in there it's worth replacing the clutch hub for a deep splined item too.
Of course, as you'll have the swing arm off, check the condition of the UJ and carrier bearing.

[Lannis]

I bought the rear main seal installation tool and have used it on two installations.

It's not absolutely necessary, but it sure is nice to just turn the bolt and know that the seal is pressing straight in, slowly and surely, and seating at exactly the right depth into the housing.

You can do it by tapping and rapping and sort of by-guess-and-by-God on the seating depth, but ....

Lannis

[blackcat]

I bought the rear main seal installation tool and have used it on two installations.



Lannis

Where did you buy the tool?

[Antietam Classic Cycle]

Where did you buy the tool?

https://www.mgcycle.com/index.php?main_page=product_info&cPath=80&products_id=2962&zenid=ab14c31cdde8e263fd4363d800ff0dcf

I think mine has been used all of once for installing a seal, I use it more as a fixture in the hydraulic press.

[Lannis]

https://www.mgcycle.com/index.php?main_page=product_info&cPath=80&products_id=2962&zenid=ab14c31cdde8e263fd4363d800ff0dcf

What he said!

[blackcat]

Thanks, guess I should have looked at MGC first. 

[Lannis]

Thanks, guess I should have looked at MGC first.

If you only think you'll need it very occasionally, I'll lend you mine, just PM.

Lannis

[Chuck in Indiana]

I didn't notice it mentioned to first check the big breather hose that goes into the bell housing. It is pretty common for them to leak and mimic a bad seal..

[blackcat]

If you only think you'll need it very occasionally, I'll lend you mine, just PM.

Lannis

Thanks, I just did one not too long ago and it doesn't leak. It's one of those installations that I have done a few times but it's always a concern given the location; a proper tool seems so comforting.

[Stu]

Thanks for all the input. Bike is now crabbed and all stripped out. Obvious leaks from rear crank seal, both ends of the gearbox, and the breather gasket, all of which will be replaced before it goes back together.

Clutches...

My bike has been fitted with an early Surflex kit as mentioned in Guzziology. These have curious sintered friction plates that are half the width of the normal ones, thinner, so use two intermediate plates and wear these steel plates badly. There are witness marks on both ends (flywheel and spring plate) but both are reusable. Centre shallow splined hub on gearbox is OK, if a little worn.

I have the options of:

 -  putting it all back together - it was working fine, but it measures below wear limits. So no.
 -  replacing just the two friction plates and one intermediate plate with new springs and reusing the shallow splined hub. Seems like false economy, but parts available.
 -  fitting a deep spline kit. Which makes most sense to me but seems to be out of stock or NLA everywhere except HMB and their kit uses Surflex plates which no one seems to like.

Anyone know anywhere else in EU that I can get a deep spline clutch kit for sensible money? Anyone using the HMB kit with Surflex plates?

 

[Chuck in Indiana]

Anyone using the HMB kit with Surflex plates?

*I don't know* if they have changed or not, but I just replaced some Surflex plates in the G5 that had roughly 15, 000 miles on them. Still looked new, but were so grabby the bike was almost unridable when hot. They also ate up the flywheel and transmission input splines.
I have some I'd give you..

[Stu]

Yeah, I've seen a few similar reports on the Surflex, so was avoiding them.

After a discussion with Gutsibits this morning, I've ordered two Newfren plates, a new intermediate, and some new springs... will reuse the old splined hub which isn't too bad.

Have to keep reminding myself I'm keeping an old bike going, not doing a restoration!

[blackcat]

I went with this kit on the Lemans:  https://www.mgcycle.com/index.php?main_page=product_info&cPath=193&products_id=4766

[Stu]

I went with this kit on the Lemans:  https://www.mgcycle.com/index.php?main_page=product_info&cPath=193&products_id=4766

"currently sold out"... as it appears to be everywhere. I'll hazard a guess they're made in batches, and currently unavailable.

[kfz]

While you're in there it's worth replacing the clutch hub for a deep splined item too.
Of course, as you'll have the swing arm off, check the condition of the UJ and carrier bearing.

Wise words mate,

If it was me an i would be replacing the no doubt simaler aged main seals in the gearbox. but then thats me.  Crabing it again to do it a week later will be undesirable.

Kev