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2005 KTM 50 SX
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Discussion Starter · #1 ·
Hi all
Very new to the forum and first time working on a KTM for my son. Long story short I picked this 2005 ktm 50sx from online selling portal for cheap. The bike starts absolutely fine but the clutch doesn't engage even at max rpm. After watching and reading few threads i believed its something to do with the spring tension and decided to do the "click" adjustment hoping the clutch will grab at a lower rpm if at all. Now, when I opened the clutch case I was expecting to see the "clutch house (?)" where I have seen in few videos where people align the three holes and twist to adjust the tension. Well this bike didn't have it and I see the three clutch setup as shown.



Is the bike missing it? Is that why the clutch is not engaging ? Or is the clutch house thingy only on certain models ?

Any guidance appreciated.
 

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Hi all
Very new to the forum and first time working on a KTM for my son. Long story short I picked this 2005 ktm 50sx from online selling portal for cheap. The bike starts absolutely fine but the clutch doesn't engage even at max rpm. After watching and reading few threads i believed its something to do with the spring tension and decided to do the "click" adjustment hoping the clutch will grab at a lower rpm if at all. Now, when I opened the clutch case I was expecting to see the "clutch house (?)" where I have seen in few videos where people align the three holes and twist to adjust the tension. Well this bike didn't have it and I see the three clutch setup as shown.

View attachment 104925

Is the bike missing it? Is that why the clutch is not engaging ? Or is the clutch house thingy only on certain models ?

Any guidance appreciated.
All looks good there. The clutch has 3 shoes. As the revs of the motor increases those 3 shoes will move out and grab the clutch drum. What regulates when that happen is a stack of cupped washers (50sx) that you can fit in different order. As you are new to this I recommend you get a workshop manual where you can find all the info you need (how to place the washers so the clutch grabs at the revs you want it to grab and more info). Our 2'nd KTM was a 2005 50sx. I had tested that the motor was running when I picked up the bike. Next day we went racing... I put the bike on the stand and it started easily. But backwheel would not spin. Confused I asked another dad, who had same bike for his son, what could be wrong. He came over, kicked the bike in to life and revved it full noise. The wheel was happily spinning! "It needs over 9000 revs to get the rear wheel moving" he told me... I had never had a bike that got even close to those revs... The 50sx has a narrow Power Band. It starts at little over 9000 and ends at approx 12500... the bike needs to be in that rev range to work properly!

So once you get over 9000 revs the clutch will grab and dirt will fly!

I also soon learned that it was best to dismantle the washers and clean them between every racing and practice day as once you get gunk on them the washer stack gets too tall and the clutch will grab too early leaving the motor with no power.

If you go to the "Bike Tips and Tricks" category you find a post with manuals. Some free, some for a fee. I recommend you get a manual for the bike. (Just checked and found the workshop manual for the 2005 50sx for a fee).

You need any more help feel free to come back.

(I will also move your thread to "Sportminicycles" where all things 50 and 65 is discussed.)
 
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2005 KTM 50 SX
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Discussion Starter · #3 ·
9000 !!! Wow that's screaming rpm.

Glad to know i am not missing any parts.

Thank you so much for looking into it for me and all the guidance.
 

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9000 !!! Wow that's screaming rpm.

Glad to know i am not missing any parts.

Thank you so much for looking into it for me and all the guidance.
Let us know how you go with the bike and how your son did. Some kids get scared when the clutch grabs. You can set the washers in a different order so the stack gets taller and grabs faster (at a lower rpm range). This will mean that he will not initially be in the Power Band (PB). But if you let him use it on a flat piece of land and not on a race track initially (as setting the clutch to grab before the PB means that he will struggle to get in to the PB of 9000 - 12500 rpm), he will get used to the bike and more brave. Once he develops you can then set the washer stacks to the recommended height and he will be able to compete with the others.
 

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2005 KTM 50 SX
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Discussion Starter · #5 ·
So I finally managed to remove the clutch off the 2005 KTM 50 which I got off an online selling portal. I am very new to KTMs and centrifugal clutch.



Can some one have a look at this and tell me if they are any good to be reused or do I need to get new ones ?

The bike came with a running engine however the clutch never engaged even at full rpm. There was pretty much no oil in the clutch case too when I removed.
 

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Here the parts in your clutch: 2005 KTM 50 SX Pro Senior LC Clutch | KTM World

#5 are the important ones. Those washers determine at what revs the clutch will engage. Normally that is between 9,000 to 9.500 revs per minute. The washers can be stacked in different sequence to achieve this. I recommend you get a service manual for the bike/motor so you can determine how to stack the washers. (Check "Bike Tips and Tricks" category for manuals and get the one that is for your bike.)

And your clutch shoes have life left in them! Just make sure that the 3 bolts are well below the clutch shoe grabbing surface as you do not want them to rub on your clutch drum!
 

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Discussion Starter · #7 ·
Hi

Disassembled the clutch and put everything back with the washers in standard configuration, revved it up and yes, we have MOVEMENT :D

Its still a bit slow to grip but I guess the washers are really worn out. I think I will just replace the complete clutch and the basket.
 

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Hi

Disassembled the clutch and put everything back with the washers in standard configuration, revved it up and yes, we have MOVEMENT :D

Its still a bit slow to grip but I guess the washers are really worn out. I think I will just replace the complete clutch and the basket.
Good work! If the washers would be "worn out" the clutch would grab earlier. That would mean that the motor would not have time to get up to the revs needed (over 9,000). Measure your washer stack with a caliper (also called a vernier). Make sure all 3 are the same height. If all is well there, then re-arrange the washers so that the stack is a fraction taller. (that means less than a millimeter taller!). Always have all 3 washer stacks exactly the same configuration and height! Yes, it is fiddly work, but if you have patience you will get there!
 

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2005 KTM 50 SX
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Discussion Starter · #9 ·
my stack config is --> HH(())(())(())()///
Stack 1 - .640mm
Stack 2 - 0.619mm
Stack 3 - 0.612mm

Big variation. Looks like I will get new washers and restack them.

Anyone here knows the dimensions for the belleville washers ? I can get them from a hardware shop (assuming they are the same as the 'KTM' OEMS )

Cheers

Eb
 

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my stack config is --> HH(())(())(())()///
Stack 1 - .640mm
Stack 2 - 0.619mm
Stack 3 - 0.612mm

Big variation. Looks like I will get new washers and restack them.

Anyone here knows the dimensions for the belleville washers ? I can get them from a hardware shop (assuming they are the same as the 'KTM' OEMS )

Cheers

Eb
A couple videos:


 
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