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Discussion Starter · #1 ·
Greetings,

I have a 69 T100R that I recently overhauled (pistons, bored, bearings, valves, clutch, & primary drive).

I have a gear oil leak. At first I thought it might be the gear box seal, but after cleaning the area and getting a closer look, the leak is coming from the clutch side of the main sprocket.

I know the clutch door seals onto the mainshaft. Is there any way to keep oil from seeping out from around the mainshaft high gear?

Thanks for all replies.
 

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Behind the front sprocket there is a seal around the mainshaft. It's easy to replace, you can do it with the transmission fully assembled and from the primary side. You do have to completely disassemble the primary and remove the sprocket, though. Sounds like you're intimate with your primary already so it will be a cakewalk for you.

Order up:
mainshaft seal (T1478)
sprocket door seal (E7565)
sprocket door gasket (E3832)
primary cover gasket (E4156)

That should be all you need to do this job.
 

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Discussion Starter · #3 ·
Thanks for the reply, but I think that seal is ok, because I've cleaned it and I don't have any oil coming from the gear case side of the sprocket, it is dripping from the clutch side of the sprocket. The main sprocket slides over the high gear splines and I think it must be coming through the bushing in the high gear. I reduced the gear oil level by 2 ounces because it leaks more overnight when it's on the kick stand. I'm going to try it tonight on the center stand. The seal on the clutch door only seals on the main shaft, I don't think it shoud be pressed in more to create a seal on the end of the high gear. I don't know. This is some of the true enjoyment of these old Brit bikes, there's always something to work on, I love it.
 

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"The seal on the clutch door only seals on the main shaft" i believe the seal on the trapdoor seals on the high gear not the mainshaft .

are you sure it's leaking on the clutch side ? and are you using the level plug in the middle of the drain plug to set the level when the bike is standing straight up ?

my guess is that it's the tranny seal behind the sprocket .

cheers , Woody
 

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Discussion Starter · #5 ·
Thanks for the reply.

I know the seal on the clutch door seals on the main shaft.

I thought there was a shoulder on the main sprocket that fits inside the gearbox seal.

I used some spray solvent and cleaned everything around the sprocket, blew it dry with air, & left it for about 3 hours on the kickstand and the drip was coming from the clutch side. The gearbox side of the sprocket was dry.

When I rebuilt the engine I bought a new drain plug because the other was stripped out. The new one was quite a bit longer than the old one so I installed it and put 2/3 of pint of oil (80w90) in the gear box, used a wire to check the level from the top, then removed the plug and shortened it to what the oil level should be (the same length as the stripped plug). I refilled the gear box, put about 100 miles on the bike and noticed the drip when cold on the kickstand. I drained the oil and put 1/2 pint of 80w140 back in, but it still drips. I'm fairly certain that it is coming from around the high gear.

I'm going to leave it on the center stand until I decide what I'm going to do.
 

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"I know the seal on the clutch door seals on the main shaft." well if it does on yours then there's your problem .

dang it's late but give me a few and i'll get you some pics .
 

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k , top of pic is a '68 on 500 gear box . arrow points to the sealing surface for the clutch door seal .

bottom is a '67 and earlier with the bushing extending which is where the seal seats .



second pic shows the clutch door and the seal on the earlier gearbox high gear . sorry but i don't have a later clutch door to show you , however the seal groove/shine on the high gear is very visible .



both of those sealing surfaces are on the high gear , not on the mainshaft .

now thing is , in my collecting parts and several gearboxes , i've found a total mish -mash of earlier and later parts . might be what's going on with yours .


cheers , Woody
 

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Discussion Starter · #8 ·
Woody thanks for the photos, but now I'm wondering which one I have. I do think the photos verify that the gearbox seal does fit over the main sprocket. That's were I thought the problem was because when I assembled it I felt like the sprocket did not have a good sealing surface. I cleaned it up as good as I could with some scotch-brite and it seemed to slide into the seal ok, and like I said that side of the sprocket is dry. Perhaps I have the wrong seal in the clutch door, however I don't recall there being something that didn't look right when I installed the clutch door.

It would drip after about an hour on the kick stand, But I'd place the bike on the center stand for about 3 hours and no drip, I'll see what it looks like in the morning.

The block # matched the frame #, but the heads and pistons where from an earlier model. It had some Jap carburetor & front fender, so no telling what the transmission is from. This has been a real pleasure to work on. I'm an old car guy and I'm just getting my feet wet with these Brit bikes. I love em, in fact I would've been a Rocker in the 60's if I wasn't such a motorhead back then.
 

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Discussion Starter · #9 ·
Thanks to all who have replied to this thread.

I believe I know where the leak is coming from. This is not uncommon. The gear box seals on the sprocket shoulder and the clutch door seals on the shoulder of the high gear. When the bike is on the kick stand the gear oil seeps through sprocket and out around the sprocket nut and tab washer. I'm pretty sure this is what it is because it doesn't drip a drop when on the center stand.

Woody, thanks alot for the photos, the first one with the arrow really helped me to understand what's going on.
 

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Discussion Starter · #11 ·
internet ay,

I haven't fixed it.

The more I have researched this, I've found that this is a common leak for these old British bikes. I like leaving it on the kick stand so what I have done is use some cloth oil absorbant rolled up like a cigar and I tye rap it to the frame just under the main sprocket. The oil never reaches the ground, however it does drip some on the chain/sprocket while it sits and some of that excess oil will drip from the rear of the chain after I take it for a long ride. This winter I think I'm going to change the front sprocket (raise the drive ratio) and I will look and see if there is something I can do to fix the leak then. I have also found out that some folks have installed O-rings (not sure where) which sometimes work.

I hate leaks, but I like working on & riding these old Triumphs so much I'm learning to say "it's just a small drip".

Good luck
 

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