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2020 790 Duke
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I have a deep-seated lack of faith in dealer mechanics and imagine they'd put the bike in 1st gear, blast the CS nut off with an impact gun, gouge the engine case as they yanked out the old seal, then impact gun on the CS nut. So I'd much rather do the work myself.
I've just ordered the Corteco seal. Will post my results. Thanks @W1d0 for the tip!
You nailed it Bob. Exactly why I do all my own work on bikes and cars.

My local dealership has a track record of doing some pretty shody work.
 

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My Corteco seal arrived today and I installed it.
It is 3mm thicker than stock but fits perfectly (better than stock?)

Thanks again @W1d0 for the tip!
Before (look familar?)
6155


Compared:
6156


Installed:
6157


Haven't had a chance to ride yet but confidence is high!
 

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2020 790 Duke
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217 Posts
Well I have now entered the murky waters of the CSS leak. Mine leaked from the day of delivery.

Been wiping things off for 2200 miles now. Last week I ordered the KTM seal kit and installed it a couple of days ago.

Yesterday after riding about 80 miles the leak was still there. Once again I wiped it down and rode about 40 miles today and the leak remains.

I did an online search and came up with the exact size as stock made by SKF which is an excellent quality product. Order placed and will install when I get it.

Stay tuned for my report with the result.

2021-01-19 (1).png
 

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My Corteco seal arrived today and I installed it.
It is 3mm thicker than stock but fits perfectly (better than stock?)

Thanks again @W1d0 for the tip!
Before (look familar?)
View attachment 6155

Compared:
View attachment 6156

Installed:
View attachment 6157

Haven't had a chance to ride yet but confidence is high!
So I have the Corteco seal, but haven't installed it yet. 2 things:
  • Can you report back with your findings? (Leak, no leak)
  • Was it difficult to change? I'm a wrencher, just never done this specifically.
 

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So I have the Corteco seal, but haven't installed it yet. 2 things:
  • Can you report back with your findings? (Leak, no leak)
  • Was it difficult to change? I'm a wrencher, just never done this specifically.
Will certainly report back as soon as I can break away from work and go for a ride!

Not difficult.
Remove cover, flatten tab on washer, removed CS bolt (step on rear brake, don't use transmission)
Loosen rear axle, push axle to the left a bit so the adjust block is clear, push rear wheel forward (to give enough chain slack to get CSS off.
I drilled two small holes in the metal face of the old seal, screwed a few sheetmetal screws in (barely in, just enough to grip, then used a claw and block of wood to gently lever out the old seal.
Cleaned the area (don't spray anything in there, just clean with a rag).
I used silicone grease on the new seal, started it with my fingers and then tapped it in with a large socket that I had that happened to fit perfectly.
Install new washer, torque to bolt to 100nm, put rest back together.
 

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Thank you very much for the detailed write up! I have two last questions (hopefully...):

  • Did yours come with a new washer? Mine did not. It's apparently an old stock Corteco 12012709B seal. It doesn't have the same writing, or really look like yours. It is a 32x47x10 Corteco seal though...
  • Why did you use silicone grease? To ease it in, prevent water intrusion, or both?

Thanks again!
 

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Thank you very much for the detailed write up! I have two last questions (hopefully...):

  • Did yours come with a new washer? Mine did not. It's apparently an old stock Corteco 12012709B seal. It doesn't have the same writing, or really look like yours. It is a 32x47x10 Corteco seal though...
  • Why did you use silicone grease? To ease it in, prevent water intrusion, or both?

Thanks again!
The washer is KTM part number 51033031000. Same part for every LC4 engine since the 90's. Not sure about the difference in the seal. Mine is the same size as yours. Box is labeled made in Germany.

I used silicone grease mainly to aid in insertion. No concern for water intrusion, if oil can't get out, water can't get in. ;)
 

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Great info jmardy!

Very strange that this is still a thing... this bike is out for a couple of years. Getting a oil seal right is not rocket science. Neither is having repair parts.

Shame on KTM for having this idiotic issue ruin an otherwise great reputation of the 790/890.
 

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It's the same seal they've been using in every LC4 engine since 2007.
They probably just assumed it would work as it has. I have an '08 690 Enduro with 20K miles on it and the CS seal has never leaked. Weird that it's an issue on the 790/890.
 

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It's the same seal they've been using in every LC4 engine since 2007.
They probably just assumed it would work as it has. I have an '08 690 Enduro with 20K miles on it and the CS seal has never leaked. Weird that it's an issue on the 790/890.
There were suggestions a while back that this problem may be caused by an overly tight chain. I have a great mechanic who told me to ignore the two different chain adjustment methods in the 2018 and 2019 790 manuals. Just wondering if the 890R manual still advises to adjust the chain with the suspension unladen and the bike on a paddock stand ? Just seems wrong to me to adjust chain not taking rider weight into account. Cheers from land of Oz
 

a d m i n .
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My Corteco seal arrived today and I installed it.
It is 3mm thicker than stock but fits perfectly (better than stock?)

Thanks again @W1d0 for the tip!
Before (look familar?)


Compared:
View attachment 6156

Installed:


Haven't had a chance to ride yet but confidence is high!

Well Done!
 

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That Corteco seal is just a standard cam/crank seal from an older VW Rabbit/Golf/Jetta/etc. Make sure you grease the inner part of the seal that rides on the sleeve, they don't last when they're dry. That one has bidirectional wipers, which I've not been a fan of (but finding a CCW wiper seal puts you into obscure VW diesel intermediate shaft territory, which is why they consolidated the two part numbers and made it bidirectional). (VW mechanic)
 
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