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Thread: Clutch set up ktm 50sx

  1. #1
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    Default Clutch set up ktm 50sx

    I just bought an 04 KTM 50sx, I purchased it sight unseen 1st mistake. It was supposed to be in race condition (wrong).

    The clutch does not hook up until you get on the pipe. How do you adjust this type of clutch? I have read about stacking but do not know what that means or where it is. Please any advise is good at this point.
    BW 200, BW 80, Polaris 50, JR 50, Z50R, KTM 525 MXC 04 50sx, Raptor 80

  2. #2
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    You need to go to ktmtalk.com. There is an entire section dedicated to the minis and much discussion of the clutch.

    How big are you? My son has one, he is 10. I really don't think these bikes are good for full grown adults, mostly due to the auto clutch mechanism. You can set the clutch up to hook sooner but you are really straining the hell out of the whole system if you are more than 80 pounds or so. Also, if you haven't done it yet...immediately drain the clutch fluid and replace it with 250ml of your preferred fluid. The manual calls for 150ml and this is not nearly enough. When it slips, it puts enormous heat into the engine and the bike will boil over. I use B&M Trick Shift in my son's bike with an additive called 2TwoCool. Both of these were recommended on KTMTalk. When I went up to 250cc the clutch immediately started to slip less and the bike stayed cooler.

    The clutch is probably the biggest tuning item on the bike. It is almost like black magic with all of these different suggested washer stacks. I have not delved into it myself as my son does not race the bike yet, he just plays with it in the dirt. It looks pretty daunting to me, actually. I am already planning the move up to a bike with a traditional transmission for him, instead of going crazy trying to learn all of the ins and outs of the centrifugal system.

    Mike

  3. #3
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    Mar 2007
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    We have been racing the KTM 50's for a little over 4 years now (with about 2 years yet to go with my little one). The clutch adjustment is not very difficult, but it must be done often to keep the bike running at a top level.

    In addition to the advice on oil capacity, here are a few pointers:
    KTMTalk is a great resource.
    The clutch springs are actually cone shaped washers. These washers can be stacked in different directions to achieve the desired engagement RPM. There are a few prefered stacks, but you will find one that your riders likes with a little testing. The main thing to pay attention to when stacking the washers is the overall stack height (should be about 0.630" to 0.650"). The stacks will look something like this (())(())(())((|| where each ( is a cone washer and each | is a flat shim washer. You can change the direction of the washers to change your engagement RPM and how hard it engages. The stack I show above is the one we have always used with an overall height of 0.650".

    The individual washers should measure at least 0.047". If they are below this throw them away.

    Don't buy the washers from your KTM dealer unless you want to pay $0.68 each. You can buy bags of 100 for about $15 from 50cc parts or C&C racing. They also have stainless steel washers available for a little more, but they last longer.

    The more often you change the clutch oil the better. If you disassemble the clutch and clean the washers they will also last longer. They quickly get caked with the clutch friction material which causes the clutch to slip. You will be able to hear a difference when it starts slipping. I usually change or clean the washers about every hour of engine run time.

    Ok, so here is the most important part of it. Listen carefully.....






    If you have the money, buy a Dominator clutch from D&D. Almost no maintenance, just change the oil often. We have been using one of these in the race bike for about 3 years now, and it works great!

    Good luck. It's not as hard as you think it is right now. Once you go through the clutch one time you will be a pro. Remember do not torque the clutch nut more than 25 ft-lbs or you can break off the end of the crank.

    Ok, I'm tired. If you still have questions, post them up and I'll try to answer.

  4. #4
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    Mar 2008
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    Excellent post kak324. As you can see, blowncummins, these things definitely require some maintenance and tweaking. I actually regret buying my son this bike because it is a maintenance hog. Yes, it is a high quality bike. Yes, it is a fast bike. Yes, it is a race bike and I knew it would require service. However, if I had researched it a bit before I jumped, I would have waited. He was driving me crazy and this KTM popped up locally for a great price. I could not pass it up. Unfortunately, an XR70 popped up the next day, for less money. I think he would have been better served by the XR.

    Mike

  5. #5
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    WOW I did not know this little bike would be so involved. I am used to his old JR50. Just gas it up and put some oil in it, has been running for about 4yrs without a lick. As far as clutch maint. does your side cover have wing nuts on it for easy access. HAHA. What I am getting at is how well has your side cover held up to accessing every hr. The other problem I have is the suspension is bouncy, nothing like my larger bike. I picked up some new fork seals and some 5w fork oil. Is there anything special about working on forks. The rear shock feels the same way what do I need to do to it. Is the shock repairable? Can I just change the oil.


    I checked out KTM Talk. Great info on that site for the clutch and forks but little on rear shock.

    Thanks for the advise.
    BW 200, BW 80, Polaris 50, JR 50, Z50R, KTM 525 MXC 04 50sx, Raptor 80

  6. #6
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    The shock is buildable. There is a rebound adjusting colar at the bottom of the shock. If adjusting that doesn't make a difference, then you should rebuild it or have someone rebuilt it. There are also aftermarket shocks available.

    One fork leg controls the compression damping and the other controls the rebound damping.

    On my clutch cover I used some yamabond adhesive, and glued the gasket to the cover. It has never leaked, and I have had it on and off well over 100 times. Just don't over torque the bolts, and you should not have any issues. The oil drain plugs are commonly stripped out so be careful there. If you continue to use the stock clutch, you will never use the drain plug anyways, just pull the clutch cover and tilt the bike over a little to drain it.

    As soon as your kid gets used to this bike, he won't want to ride the XR again.

  7. #7
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    who sells aftermarket shocks for these bikes and have tried different levels of oil on the forks how much oil do you use.? There is not a KTM dealer within 100 miles of me. I need some advise about online parts that are resonable. Are these the main shops to get parts for these little bike. 50cc parts or C&C racing.
    BW 200, BW 80, Polaris 50, JR 50, Z50R, KTM 525 MXC 04 50sx, Raptor 80

  8. #8
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    I don't recall the fork oil level off the top of my head. I would have to dig through my notes to tell you the effect of the oil volume and what we use.

    Paolli makes an aftermarket shock as well as Curnutt. I think they are fairly pricey. I'm not sure if Ohlins makes one small enough for the 50, but that is who I would check first. If it were mine, I'd have the shock serviced and revalved.

    There are free online manuals at www.munnracing.com. Go to shop online and look in the lower left hand corner. You can get the owners manual and parts manual. These are very helpful.

    50cc parts and C&C racing specialize in aftermarket parts. For OEM stuff, I go to Chip at Munn Racing. Same link as above. He has most everyting and is fast to ship. I have a KTM dealer 10 miles from here, but I buy from Chip. Service and part availability are important in this business. Chip is great at both.

  9. #9
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    That sounds great. I pulled some of the plastic off to repack my silencer and found that the frame has a crack in it next to the silencer bolt under the seat and down by the right peg where the pipe bolts on. Are these frames prone to cracks and is there anything I can do to prevent this problem.
    BW 200, BW 80, Polaris 50, JR 50, Z50R, KTM 525 MXC 04 50sx, Raptor 80

  10. #10
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    Well I went to munnracing.com and my 04 manual is not available for viewing, I could view 99 and 06. On the 06 it shows the lower bolt on the fork is for adjusting compression and rebound. I did not want to force this one loose, is it supposed to be tight.
    BW 200, BW 80, Polaris 50, JR 50, Z50R, KTM 525 MXC 04 50sx, Raptor 80

  11. #11
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    There hasn't been a change to these bikes in years or more except for "Bold new graphics", so the '06 manuals will do.

    The rebound adjuster is a collar that should move by hand. I think there are about 7 clicks to it.

    The frames do crack if they are jumped hard. I've had to weld ours before. C&C racing makes a frame brace that is supposed to help. Since we started roadracing these bikes, we haven't had any more frame cracks.

  12. #12
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    My boys saw the pic by your name and thought it was cool. That road racing looks fun and less stressful on the equipment. Do you have anymore pics from the track with the 50
    BW 200, BW 80, Polaris 50, JR 50, Z50R, KTM 525 MXC 04 50sx, Raptor 80

  13. #13
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    There is a really good one here http://www.mmracing.biz/ at the bottom of the page (thanks Wayne and Cam!)

  14. #14
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    Blowncummins,

    How did the clutch service go? Is you boy getting used to the bike?

  15. #15
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    I am still waiting on parts to come in from K2. I ordered some adventure springs per there advise. Come to find out they were on back order and I still have not seen them. Wish I would have know that because I order some other stuff from Munn and it came in the next day.

    But I did get the water pump replaced and the front caliper rebuilt so when I get the clutch fixed the bike will be ready to ride.
    BW 200, BW 80, Polaris 50, JR 50, Z50R, KTM 525 MXC 04 50sx, Raptor 80

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