KTM 50's (3 shoe) Clutch Drum Inside diameter

[entrpner71]

Please help, finally got around to opening up my son's engine to see why it was bogging up hill and crawling away at start up. Expected broken or severly worn springs and instead I find a 3 shoe clutch:confused:?. That is very odd becasue he has a '98 MA and they use a 2 shoe clutch with springs not washer stacks. It fits okay but I noticed it seemed like there was excessive space btwn the pads and the drum's interior contact surface. If I know the hub's interior diameter I can put a washer to bring the tolerances within spec (hoping the pads will still engage correctly even though the circumfrances will be a little different). I would really like to keep the 3 shoe clutch esp since it has damaged the drum and a new one (98 drum) is over $200 not including the clutch (2 shoe) itself:banghead: I set her up and she won't spin the rear tire even at WOT. So it is either over tightened or needs a shim.

this should be the drum for any '02 to '08 (3 shoe) clutch ktm 50s all I need is the inside diameter, if you have one out other dimensions and pic would be even better:banana:

Help please if somebody could pop thier clutch cover to take a quick measurement I would really appriciate it:worthy: Bought him all new gear but need to have this done before xmas. Even if you are changing the oil just pop a couple bolts and measure her before adding new oil. Thanks for the help:thumbsup: Posted this on KTMtalk over a week ago and still nothing from anybody:banghead:

[Superbike Mike]

If the drum is not wore and grooved it is good. The problem is the washer stack is crapped out. It needs restacked. The other issue is wiggle the shoe on the triangle. They tend to get wore out also. You probably need the 3 shoes, a bag of clutch washers and new center bolts. There is a great video out there that helped me greatly. I will see if i can find it. It is not bad at all once you understand the basics.

[Superbike Mike]

http://www.motomx.com/clutch_information.html

[entrpner71]

the drum is groved:cry: or I would just install the 2 shoe while I figured out if the 3 shoe is viable.

Again this does not fit perfect, the clutch shoes and pad stick out of the drum a good couple mm. It presses on perfectly but once on it seems to have a lot of space between the drum and pad surface.

I did buy new SS washers and installed them for the beginner/intermediate rider based on the suggestions found in the KTM bible. The collars that fit over the screws are worn bad too but I don't want to spend any more $ until I know that this set up will engage. The previous owner just had the washer stacks stacked so that it would could move out several mm by simple gravity in my hands.

will post the pics here, listed them in a separate thread in the mini section to those unsure of what to expect

P.S. remember the clutch drums for the 97-01 are different then the clutch drums for 02-08. The way the gears interact are visible in the microfiche. My sons are off angle to their axis while the 02-08 run parellel with the crank shaft.

Thanks for the link and response, will look into it tonight.

[entrpner71]

short on time, here is the link to my post, 9th post down

https://www.thumpertalk.com/forum/showthread.php?t=918215&page=4

[bronc3]

You can run the coil springs in the three shoe clutch if you desire to do so. Newer M/As come with a three shoe clutch and the "green" coil springs. This makes the clutch act "PW-ish".

If you stay with the bellevue spring washers, make sure your spring bolts aren't grooved up. Look inside the clutch shoe recess for wear grooves from the washers as well. Deep grooves won't allow the spring washers to move smoothly as the clutch engages and disengages, kind of like a grooved up basket on a big bike.

Sounds like you already know you can shim the shoe closer to the drum to adjust the clearance ( 1 - 2 mm I think) to compensate for wear, but if you like you can shim the spring washers tighter as well to raise the engagment point too.

As long as your drum is not severely grooved, it will work fairly well for casual use. If you wind up rebuilding, the "red" shoes have a different face design that doesn't groove up clutch drums.

[entrpner71]

You can run the coil springs in the three shoe clutch if you desire to do so. Newer M/As come with a three shoe clutch and the "green" coil springs. This makes the clutch act "PW-ish".

No, he well beyond the PW even with basic mods (K&N filter, boyseen reeds, jetting, 70 main) still has it pinned and was getting bounced off by the suspension... well lack of it:smirk:

If you stay with the bellevue spring washers, make sure your spring bolts aren't grooved up. Look inside the clutch shoe recess for wear grooves from the washers as well. Deep grooves won't allow the spring washers to move smoothly as the clutch engages and disengages, kind of like a grooved up basket on a big bike.

did SS washers off ebay, made in USA and high precision. Not sure what brand but they did look high quality. Marks are easily visible on the collar, a good mm or so into the material, could that be my engagement trouble? Again the rear wheel never moved at WOT. Will buy new bolts and spacers either way, could the damaged ones ruin my new washer stacks?

Sounds like you already know you can shim the shoe closer to the drum to adjust the clearance ( 1 - 2 mm I think) to compensate for wear, but if you like you can shim the spring washers tighter as well to raise the engagment point too.

If you could get that actual number I would be so appreciative:worthy: I was only asking for the ID so I could get a strong indication of what shim thickness I need for this. Don't need higher engagement rpm, I need lower. I don't want the bike pegged just to start up, he will get scared off or hurt. I want a good linear hit for him, so he can climb up hills without bog, get her bucking yet still have control for tight areas etc.

As long as your drum is not severely grooved, it will work fairly well for casual use. If you wind up rebuilding, the "red" shoes have a different face design that doesn't groove up clutch drums.

I have seen those, I don't want to buy a new clutch because the drum is shot and it would ruin the new clutch. I don't want to buy a new drum because (they are over $200) and the old one does not fit the the 3 shoe, it is to shallow for the clutch depth and to big for the clutch diameter. On top of all this the microfiche shows that the original parts both clutch and drum have been changed to a new one post 01 but does not tell us to what, not even sure if the new superceeded part is a 2 shoe clutch. He found out that the drum was changed in 01 and is the stock part #. Spoke to my dealer and he is going to contact KTM for me to know what is going on.

By the way to anybody looking for help with their older KTMs, this is your guy, ask for him by name though, he is IMHO exceeded every other person I have dealt with. Andy is my parts dealer(unless ebay is much cheeper:smirk:)

Big thanks to Andy at North County Yamaha in San Marcos CA. They are authorized KTM dealers, regular pricing on parts but he has spent hours helping with a mixup error (on KTM's behalf) for a $2 part:thumbsup: Very nice, if he doesn't know, he will get you an answer and keep you posted until he does get questions/problems resolved:banana:

[bronc3]

No, he well beyond the PW even with basic mods (K&N filter, boyseen reeds, jetting, 70 main) still has it pinned and was getting bounced off by the suspension... well lack of it:smirk:

did SS washers off ebay, made in USA and high precision. Not sure what brand but they did look high quality. Marks are easily visible on the collar, a good mm or so into the material, could that be my engagement trouble? Again the rear wheel never moved at WOT. Will buy new bolts and spacers either way, could the damaged ones ruin my new washer stacks?

If you could get that actual number I would be so appreciative:worthy: I was only asking for the ID so I could get a strong indication of what shim thickness I need for this. Don't need higher engagement rpm, I need lower. I don't want the bike pegged just to start up, he will get scared off or hurt. I want a good linear hit for him, so he can climb up hills without bog, get her bucking yet still have control for tight areas etc.

I have seen those, I don't want to buy a new clutch because the drum is shot and it would ruin the new clutch. I don't want to buy a new drum because (they are over $200) and the old one does not fit the the 3 shoe, it is to shallow for the clutch depth and to big for the clutch diameter. On top of all this the microfiche shows that the original parts both clutch and drum have been changed to a new one post 01 but does not tell us to what, not even sure if the new superceeded part is a 2 shoe clutch. He found out that the drum was changed in 01 and is the stock part #. Spoke to my dealer and he is going to contact KTM for me to know what is going on.

By the way to anybody looking for help with their older KTMs, this is your guy, ask for him by name though, he is IMHO exceeded every other person I have dealt with. Andy is my parts dealer(unless ebay is much cheeper:smirk:)

Big thanks to Andy at North County Yamaha in San Marcos CA. They are authorized KTM dealers, regular pricing on parts but he has spent hours helping with a mixup error (on KTM's behalf) for a $2 part:thumbsup: Very nice, if he doesn't know, he will get you an answer and keep you posted until he does get questions/problems resolved:banana:

I was only saying the clutch will engage at low rpm, similar to a PW's clutch behavior, if the springs are tired or shimmed too soft. On KTM/LEM/Cobra/etc. two strokes, if it is too soft the bike won't even come on the pipe at times.

Usually the grooves will prevent the clutch from engaging and/or cause it to hang up partially engaged if the grooves are deep enough for the edges of the springs to get caught in.

I can't give you a good ID as all six of my drums are worn to some extent. I shim the shoes to compensate, looking for 1-2 mm clearance, and it works for my kids.

If I had the budget, I would be running all new clutches in both bikes, or go for the Tomar. I don't have it right now, so I shim them to work. It is a pain and a lot of trial and error, but it works.

[shortyr6]

No, he well beyond the PW even with basic mods (K&N filter, boyseen reeds, jetting, 70 main) still has it pinned and was getting bounced off by the suspension... well lack of it:smirk:

did SS washers off ebay, made in USA and high precision. Not sure what brand but they did look high quality. Marks are easily visible on the collar, a good mm or so into the material, could that be my engagement trouble? Again the rear wheel never moved at WOT. Will buy new bolts and spacers either way, could the damaged ones ruin my new washer stacks?

If you could get that actual number I would be so appreciative:worthy: I was only asking for the ID so I could get a strong indication of what shim thickness I need for this. Don't need higher engagement rpm, I need lower. I don't want the bike pegged just to start up, he will get scared off or hurt. I want a good linear hit for him, so he can climb up hills without bog, get her bucking yet still have control for tight areas etc.

I have seen those, I don't want to buy a new clutch because the drum is shot and it would ruin the new clutch. I don't want to buy a new drum because (they are over $200) and the old one does not fit the the 3 shoe, it is to shallow for the clutch depth and to big for the clutch diameter. On top of all this the microfiche shows that the original parts both clutch and drum have been changed to a new one post 01 but does not tell us to what, not even sure if the new superceeded part is a 2 shoe clutch. He found out that the drum was changed in 01 and is the stock part #. Spoke to my dealer and he is going to contact KTM for me to know what is going on.

By the way to anybody looking for help with their older KTMs, this is your guy, ask for him by name though, he is IMHO exceeded every other person I have dealt with. Andy is my parts dealer(unless ebay is much cheeper:smirk:)

Big thanks to Andy at North County Yamaha in San Marcos CA. They are authorized KTM dealers, regular pricing on parts but he has spent hours helping with a mixup error (on KTM's behalf) for a $2 part:thumbsup: Very nice, if he doesn't know, he will get you an answer and keep you posted until he does get questions/problems resolved:banana:

your drum ID should be no more than 84mm max.....OD drum 82 min. if it is grooved, get a new clutch and drum. hate to say it, but these are just regular maintenace items. some of the top racers change these out after every couple motos for new ones.

Edited December 9, 2010 by shortyr6

[bronc3]

some of the top racers change these out after every couple motos for new ones.

I'll take all the two-moto used drums I can get. ?

I'd be scared to measure the one I set up today.

[shortyr6]

I'll take all the two-moto used drums I can get. ?

I'd be scared to measure the one I set up today.

my pockets are not that deep either. i make the clutch last as long as i can.

[entrpner71]

I actually had a good idea, I am going to take the clutch drum to a machinist to see if he can clean up the damage and press in a steel sleeve/collar that matches the dimension of the 02+ clutch drum. Then I don't have to replace her and I can keep the 3 shoe clutch in the bike (I would buy a new clutch of course) Anybody familiar with this process and if it could work?

[bronc3]

I actually had a good idea, I am going to take the clutch drum to a machinist to see if he can clean up the damage and press in a steel sleeve/collar that matches the dimension of the 02+ clutch drum. Then I don't have to replace her and I can keep the 3 shoe clutch in the bike (I would buy a new clutch of course) Anybody familiar with this process and if it could work?

No doubt it is doable, but probably not cost effective.

I have access to a lathe and have considered cleaning a few of ours up, then shimming the shoes to the correct clearance. Whatever amount you shim between the shoe and hub, you subtract from the stack shims. It works fine, even without cleanup.

[shortyr6]

dont think the wear in tear on the chickens ass is worth the price of the egg.

[entrpner71]

No doubt it is doable, but probably not cost effective.

I have access to a lathe and have considered cleaning a few of ours up, then shimming the shoes to the correct clearance. Whatever amount you shim between the shoe and hub, you subtract from the stack shims. It works fine, even without cleanup.

I thought about doing that to but then I realized that the diameters of the shoes would not longer match the drums and you will only have contact around the screw esp if I take off additional material... kind of like taking my son's shoes and putting them against my s10 rear drum brake. The contact area would be very small % of the total clutch pad surface area.

The drum is machined to match the gear so you can only buy them as a set @ over $215 and a new clutch assembly add another $219 for the clutch mod kit... not even sure what it includes.

Given that I think it would be worth it:smirk: That or the martin slater off ebay for $60 but still getting nailed by the drum:banghead:

[shortyr6]

if you are not doing AMA races, a tomar clutch is the way to go. I have one in our Jr and it is maintenance free.

in our Sr we have a 3 shoe and its a PITA changing oil and pulling the clutch all the time.

[entrpner71]

if you are not doing AMA races, a tomar clutch is the way to go. I have one in our Jr and it is maintenance free.

in our Sr we have a 3 shoe and its a PITA changing oil and pulling the clutch all the time.

I don't think they sell one for the 97-01 models do they? If so do you know where I could get one?