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rear main seal -- do I replace it?

KnowFear

Cruisin' Guzzisti
Joined
Feb 2, 2011
Messages
103
1983 LeMans III with @ 19,000 miles: The engine & transmission are apart to install deep-spline clutch. Do I replace the non-leaking main seals while everything is apart?

If "yes", then how do I remove the engine's rear main seal?
 
KnowFear said:
1983 LeMans III with @ 19,000 miles: The engine & transmission are apart to install deep-spline clutch. Do I replace the non-leaking main seals while everything is apart?

If "yes", then how do I remove the engine's rear main seal?

I'd recommend replacement just because of the age of the seal, and the labor involved to get there. Also all the seals and o-rings for the transmission. The way I get the seal out, is to very carefully drill two holes 180 degrees apart. Be sure to stay away from the crank and bearing housing. Screw in sheet metal screws, and pull out on the screws to get the seal. If you don't have the seal driver for the rear main, be sure to only drive the seal flush with the rear bearing housing. It can go too deep causing you another problem. If you are uncomfortable doing this, I suggest you take the engine and transmission to a reliable shop that has done this type of work before. Do you have the tools to get the clutch centered, and the hub gear as well?
 
I use a little stop collar with a set screw on the drill bit to prevent it from banging into the bearing when the bit breaks through the seal. Then I use a blind hole bearing puller (same as dent puller) with a brass tip that holds a screw.

I used to dimple the seal on a line through the center then pull it out with a hook at a 90 degree point. But that didn't always go so smoothly and sometimes took too much time.
 
KnowFear said:
Would it be bad to use a seal puller like this http://www.amazon.com/Lisle-56750-Seal- ... B0002SRCKG
and simply lever against the end of the crankshaft?

Yes, you will probably scratch the crankshaft then a new seal will ever work again. You will also need a tool for the gland nut on the transmission shaft and something to hold the hub gear. To get the transmission seal, I use an old cotter pin pulling tool. If you touch the transmission shaft, it won't matter as the new seal will ride on the new hub gear. Don't forget to use new o-rings there too. Use a quality cotter pin puller http://www.grainger.com/Grainger/wwg/se ... 16162508:s as a cheap one will probably fail (break) and give you a completely new set of problems. Also one of these for the gland nut on the transmission is good too. http://www.mgcycle.com/product_info.php?products_id=657
 
john zibell said:
KnowFear said:
Would it be bad to use a seal puller like this http://www.amazon.com/Lisle-56750-Seal- ... B0002SRCKG
and simply lever against the end of the crankshaft?

Yes, you will probably scratch the crankshaft then a new seal will ever work again.

What I meant is that the tool would rest on the end of the crank with the hook pointed towards the outer diameter of the seal. The hook would not be anywhere near the sealing surface on the crankshaft.
 
KnowFear said:
john zibell said:
KnowFear said:
Would it be bad to use a seal puller like this http://www.amazon.com/Lisle-56750-Seal- ... B0002SRCKG
and simply lever against the end of the crankshaft?

Yes, you will probably scratch the crankshaft then a new seal will ever work again.

What I meant is that the tool would rest on the end of the crank with the hook pointed towards the outer diameter of the seal. The hook would not be anywhere near the sealing surface on the crankshaft.

How do you plan to get the hook through the seal? I wouldn't use it. I will only use that type of tool when the cover is removed and the shaft isn't anywhere near it. It is your bike, if you choose to damage the crank, go for it.
 
Damage is certain, so even if you didn't care about the crank it won't work because the crank projects out too far past the face of the seal; you won't have a good purchase for the Lisle seal puller.

That cotter pin puller looks good. Do you pull straight out? I've used a smaller 90 degree pick but couldn't get a strong enough grip on it to keep it from coming out of my hand.
 
Rafael said:
That cotter pin puller looks good. Do you pull straight out? I've used a smaller 90 degree pick but couldn't get a strong enough grip on it to keep it from coming out of my hand.

Both pull and lever, but It won't work for the rear main. I only use it for the transmission/gearbox input and output seals if transmission disassembly is not required for the job.
 
thanks John, Boy, I can't remember how I got those out before. If I drilled or not, or if they came out easier because they are smaller. Anyway, do you drill to get the cotter pin puller in or get it past the lip?
 
Thanks - all good points. I will use the drill-two-holes-180-degrees-apart method.
 
Rafael said:
thanks John, Boy, I can't remember how I got those out before. If I drilled or not, or if they came out easier because they are smaller. Anyway, do you drill to get the cotter pin puller in or get it past the lip?

With the hub gear off, and the speedometer drive off, there is no need to drill. Also that way you don't mess up where the seal contacts the hub gear of speedometer drive gear. If you are working on older bikes, there is a range of machining in the 80s when the surface of the speedometer drive gear was very rough from the factory, or as a replacement part. I wouldn't install them until I had smoothed them down by either cleaning the surface up in a lathe, or chucked up in a drill press. I used a file and then fine emery paper to get a good smooth surface on the drive gear.
 
Aargggh. I destroyed the new seal while pressing it on. I wasn't paying close enough attention to the lip and a short section of it folded over. I didn't see that until I removed my pressing piece... After a choice expletive, I drilled another hole, and pulled another main seal <groan>.

So, is it necessary to use the specific Corteco brand seal for the main seal? If not, then I may be able to source a similar seal locally from an industrial supply store. Otherwise I'll be waiting at least week.
 
KnowFear said:
Aargggh. I destroyed the new seal while pressing it on. I wasn't paying close enough attention to the lip and a short section of it folded over. I didn't see that until I removed my pressing piece... After a choice expletive, I drilled another hole, and pulled another main seal <groan>.

So, is it necessary to use the specific Corteco brand seal for the main seal? If not, then I may be able to source a similar seal locally from an industrial supply store. Otherwise I'll be waiting at least week.

As long as it is the same size, material, and type, a locally procured seal should work. If you want extra piece of mind, order one from a dealer/supplier.
 
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