Final drive big seal replacement

[montmil]

One of the special tools all air head owners should have is a heat gun. Don't try to beat aluminum cases to disassemble. 

Excellent advice. Should you be anywhere near a Harbor Freight store, they have a two-temp heat gun for around $8.00. Mine has been in service for 7-8 years.

What's holding the crown gear and spline within the Cardan cover is the snug fit of the race/s of that big ol' ball bearing. Follow Señor Clubike's suggestion: support the Cardan on a couple 2x4 scraps. Apply heat. Don't worry about the old seal as it's going to be replaced. By the time the spline and Cardan reach "spit sizzle" temps, the crown gear will likely fall away of its own accord. If not, a gentle tap on the spline gear's end will move it out.

[Kookaburra]

Okay scored a heat gun and following the clear instructions from Mrclubike and montmil the crown gear and spline assembly dropped sweetly on to the bench. Only trouble is the partner spied the heatgun and now wants me to use it on several hectares of paint that is overdue for attention.

[Kookaburra]

Now thinking about reassembly. Remembering the housing is still attached to the swing arm, from reading Clymer the sequence would appear to be:  
1.Warm and lube outside of the new seal and inside of housing cover. Tap seal squarely into place from the outside of the housing cover.
2. Reseat steel baffle into housing.
2. Put ring gear assembly in freezer for 30 mins. Refit ring gear into the housing.
3. Place trimmed beer can onto ring gear and lube.
4. Install paper gasket onto housing.
5. Heat housing cover, align with paint marks and install by easing housing cover over beer can and  slowly sliding down.
6. Tap around cover perimeter until cover bottoms out.
7. Install bolts and tighten in crosswise pattern to under specified torque value. :-/

I have some questions and need to check assumptions. Most important one is-
1.  Contrary to the steps outlined above, do I fit the new seal and then the ring gear into the housing cover prior to refitting the gasket and housing cover on to the housing as one unit?
2. How deep should the new seal be?  ( I have no wear marks to guide positioning of the new seal. Picture in Clymer's seem to show it flush with, or just below the surface of the housing cover.)
3. Luca said (in a previous post in this thread) there is a need to get the paper gasket in the right way.  Looking at the new gasket -one side has writing on it and one side doesn't. So does the side with the writing face the gear housing or does it face the housing cover? and why does it matter?
4. Do I use gasket goo (eg Hylomar) on one or both of the housing or housing cover surfaces?

[montmil]

Now thinking about reassembly. Remembering the housing is still attached to the swing arm, from reading Clymer the sequence would appear to be:  
1.Warm and lube outside of the new seal and inside of housing cover. Tap seal squarely into place from the outside of the housing cover.
2. Reseat steel baffle into housing.
2. Put ring gear assembly in freezer for 30 mins. Refit ring gear into the housing.
3. Place trimmed beer can onto ring gear and lube.
4. Install paper gasket onto housing.
5. Heat housing cover, align with paint marks and install by easing housing cover over beer can and  slowly sliding down.
6. Tap around cover perimeter until cover bottoms out.
7. Install bolts and tighten in crosswise pattern to under specified torque value. :-/

I have some questions and need to check assumptions. Most important one is-
1.  Contrary to the steps outlined above, do I fit the new seal and then the ring gear into the housing cover prior to refitting the gasket and housing cover on to the housing as one unit?
2. How deep should the new seal be?  ( I have no wear marks to guide positioning of the new seal. Picture in Clymer's seem to show it flush with, or just below the surface of the housing cover.)
3. Luca said (in a previous post in this thread) there is a need to get the paper gasket in the right way.  Looking at the new gasket -one side has writing on it and one side doesn't. So does the side with the writing face the gear housing or does it face the housing cover? and why does it matter?
4. Do I use gasket goo (eg Hylomar) on one or both of the housing or housing cover surfaces?

This really is a case of "assembly is the reverse of disassembly".

I have never needed to heat the Candan nor the seal. Use gear oil to lube the seal's outside diameter and its machined location. Position the seal square to the bore. I'll use a 2-3 inch length of hardwood and a small mallet to gently 'encourage' the seal into place. Work around the perimeter and check for square each time you tap the wood block.
   Flush with the Cardan or just a smidgen below is good. If you see no wear marks on the spline gear to seal contact points, you're golden.

Use your beer can and refit the crown gear into the Cardan on the bench after chilling the gear in the freezer. The 'steel baffle' is a critical shim used to position the crown gear to the final drive gear. Put it back where you found it!

Confirm position of new gasket by double-checking no bolt holes nor brake cam opening blocked. Printing in or out is not critical. Alignment is. No gasket goop needed. Use a dab of grease to hold gasket in position. Same with the shim, if needed.

The rest is cake. If necessary, rotate the spline shaft to help engage the crown gears. Seat the cover and began bolting it up. Tighten in a criss-cross method and mind the torque requirements.

It's now time to empty a couple more 'seal protectors'. Sing out if you have other questions.

[Kookaburra]

I thought after all the useful expert advice and tips I got from the gurus on replacing the big seal in the bevel housing I should report back. (They call it an attempt at closure but really there is no such thing with a 30 year old motorcycle.)
The heating for disassembly and freezing for reassembly processes worked a treat as did the home constructed special tool (AKA the customised beer can). - (Plenty of lube and go slowly.) Also of value was the tip of using the axle as a centring guide for reassembly. Found it is important to get the gasket round the right way (only because the holes don't line up if you don't.)
Only dissonant note is breaking 2 cover bolts (at well below the torque values in the Clymer manual) and this is after carefully putting copper based anti seize on the bolts and running them in and out of the housing. At some stage I am going to have to figure how to extract the stumps but so far it has not led to any leaks.
So questions.
Why did the bolts break at very low torques? Should I have reamed the threads, replaced the bolts with new or used a gentle persuader to ensure the cover was completely seated prior to final cross torquing?
 What methods are there to remove the broken bolts from the housing?

[montmil]

If you decide to remove the Cardan cover, you may get lucky and find enough bolt sticking up to remove it fairly painlessly. Likely you have touched on the reason for breaking the bolts. Cardan cover should have been completely seated before snugging down the bolts. I wonder what was creating the resistance.

If the bolts are broken below the gasket surface, they might be removed using a left-handed drill bit. Likely no drag on the remnant bolts as the tension has been released so as the lefty drill bites, the stub should back out. Forget using an easy-out tool. More often than not, the brittle tool breaks off in the bolt and then you really are up S**te Creek with no paddle.

For now, if'n it ain't leaking, don't fix it. Just my modest opinion.

[mrclubike]

If the bolt is to hard to drill with a left hand drill bit
I don't know if you have clearance but you can take a Dremel tool with a thin small cut off wheel and cut a slot in the end of the broken bolt and back it out with a screw driver .
like Monte said it should back out easily
 The vibration of the engine may rattle it out  

[Kookaburra]

Montmil,s advice is good (as always!) if it ain,t leaking don't fix it. Which brings me on to the left hand drill bit. This sounds a bit like being sent as young motorboy to the bottom of the engine room to get a bucket of steam but as two gurus have mentioned it, I'll try and buy the solution and the drill. The bolt has a 13mm head and a solid dia of approx 5mm. What size left hand drill should I buy?

[Barry]

You might need 2 drill bits, One that's small enough to leave some strength in the bolt to get it turning i.e. 1mm smaller than the the root size of the bolt (sometimes called the minor diameter) and just in case that doesn't do it you might need one the actual root size to drill the bolt out. If it's that bad though you can always use a RH bit to drill it out.

Drill bits are not much less fragile than an easy out so take care not to snap the drill.

As to why they sheared besides it not being unknown for Clymers to get the torque figures wrong they might be specified for dry threads and would then need a 30% reduction if lube of any kind is used.

[montmil]

Occurred to me later in the day... The crown gear must fully engage the pinion gear for the cardan cover to fully seat. It may be the gears are not meshing and need some encouragement. If the cover doesn't want to go down easily, grab the spline gear and rotate it a bit. That happen on my R100S after replacing the gasket. Slight turn and, plop, she's there.

[Bob_Roller]

Left hand drill bit works great to get a bolt out that isn't seized .

[Kookaburra]

Montmil said,
"The crown gear must fully engage the pinion gear for the cardan cover to fully seat. It may be the gears are not meshing and need some encouragement."

Spot on I had to do the spline wiggle during reassembly and prior to cross torquing the bolts. Have now done 150 kms with no sign of leak or lack of meshing.

Barry said,
 "it not being unknown for Clymers to get the torque figures wrong they might be specified for dry threads and would then need a 30% reduction if lube of any kind is used.

I was aware of this lube/non lube issue and having lubed the threads I had  the torque wrench set for 8fp.  Clymer spec for dry threads housing cover nuts was 13fp.  It is a big torque wrench that I don't think does low torque values very well and I probably didn't ensure the cardan cover was completely seated prior to commencing cross torquing.