[glassdimly]

I've got an 85 GL1200 interstate that I recently acquired which is leaking engine oil from the rubber boot where the final drive shaft attaches to the engine. The engine oil is very low. The engine sounds very good. There is a little knocking occasionally during a short ride, but it settled down when hot.

It may also be leaking drive shaft oil from that same boot. The crush ring on it is clearly damaged, and so is the boot.

Which part numbers should I be replacing here? Honda Motorcycle 1985 OEM Parts Diagram for Final Driven Gear | Partzilla.com

Or, since it's leaking engine oil, do I need to be looking into parts in the engine rather than the final drive?

 

[JamesPal]

There are two seals on the 1200 drive shaft. #11 on this page: Honda Motorcycle 1985 OEM Parts Diagram for Rear Case | Partzilla.com and #29 on this page: Honda Motorcycle 1985 OEM Parts Diagram for Swingarm / Driveshaft | Partzilla.com. I suggest replacing both while you are in there. Also, it is not good to run the bike with the engine oil very low.

 

[DaveO430]

Is it loosing final drive oil? That would be more apparent than engine oil since it holds so little oil.

 

[glassdimly]

@DaveO430 I just drained out 5.5 ounces from the final drive. So that's full, huh? It's not leaking then?

@JamesPal Thank you. What other parts should I replace when I'm in there? I'll definitely not be running it now that I have discovered the oil level.

This seems like a complicated repair. I'm stripping of the panniers to get it into the basement. Think it's doable without getting too deep into the engine?

 

[Sprocketrocket55]

Get an OEM manual on ebay

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[Bike...and Dennis]

Two places can leak. Rear engine seal and final drive pinion seal. They are both fairly complex fixes and if you don't have the knowhow, and tools, take the bike to someone who does.

 

[dusterdude]

If its the same setup as an 1100,you need to remove the rear wheel then the final drive from the swingarm.you can leave the swingarm attached to the bike but you'll need a long set of snap ring pliers to get inside the swingarm to remove the snap ring that holds the coupler onto the final drive splines.then you need to remove the snap ring at the engine joint.

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[glassdimly]

@Bike...and Dennis What specialized tools are needed? I can handle "fairly complex" if I have a manual and can lay stuff out on cardboard with notes. But I don't have a bunch of special Honda tools. Snap ring pliers I can buy.

 

[Sprocketrocket55]

The manual says to pull the engine to do rear cover removal. They are talking about getting the seal replaced without removing the engine.

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[glassdimly]

Ah so you all agree I need to pull the engine if I need to replace the rear engine seal and final drive pinion seal?

 

[Sprocketrocket55]

I've never done it but it sounds like you just have to get the U-joint out of the way and then work the seal out and a new one back in

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[Bike...and Dennis]

A shop changed my rear seal without pulling the motor. I don't think they even removed the swingarm. However, it's an '87 and I think they are different than earlier models.

Read this: oil leak from shaft boot? '87 interstate
You may have a simple to fix problem.

 

[DaveO430]

Ah so you all agree I need to pull the engine if I need to replace the rear engine seal and final drive pinion seal?

No, you should be able to do it by removing the final drive and pulling the boot & drive shaft back out of the way.

 

[Sprocketrocket55]

When removing the drive and shaft assembly the u joint stays behind. You would still have to move the U-joint off the engine output shaft

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[Bryanlj]

When working for a Honda dealer years ago i found it easier to remove the swing arm, just need the special socket for castellated locking nut

 

[Bike...and Dennis]

I'm told this is the tool for the swingarm. I haven't tried it, but it looks right.

https://www.amazon.com/gp/product/B000AO9S68/ref=ox_sc_saved_image_10?smid=A65TJF073FXTY&psc=1

 

[Bryanlj]

The tool looks like that but not sure that is the correct size, try ebay

 

[Sprocketrocket55]

Lock nut wrench P/N KS-HBA-08-469 or make one. And specific torque values need to be followed

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[Bike...and Dennis]

Others on this forum claim the Park Tool socket is the correct size.

 

[Bryanlj]

As a geratric old fart i do not own nor ride and in fact have never ridden push bikes so i simply dont know