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What should I look out for on a used 520sx?

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I made a post in the general section, and figured I might do better with this question here.

I am in the market for a used thumper and think I have pretty much decided I want a 520sx. I looked at a used 03 last week that seemed pretty solid, and am planning to look at another local 03 520sx before I decide.

I was hoping that you KTM guys could fill me in on what to look out for so I don’t end up with a clunker. Do they have any issues in general besides people saying they have soft suspension out of the box?

I have owned 2 strokes in the past so I know the general stuff, but I guess you could say I am a bit scared I will end up with motor that’s a 4 stroke hand grenade.

So what should I watch out for on a used 520sx 🙂

Thanks

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I too am looking at a used 2001 520 sx or mx I cant remember. Any issues with this bike? also there appears to be a weep hole on the left side of the head or jug does this ever weep oil or is this a sign of a major problem or just over filling the oil level

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I too am looking at a used 2001 520 sx or mx I cant remember. Any issues with this bike? also there appears to be a weep hole on the left side of the head or jug does this ever weep oil or is this a sign of a major problem or just over filling the oil level

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Actually you have touched on a concern. The weep hole is a port that goes between the cam seals to the waterpump. There are 2 seals with a small area between them when the seals start to wear you will either get oil (if it is leaking to the rocker arm area) or water (if it is leaking towards the waterpump). Any weeping is a sign that the cam bearings should probably be replaced. I ignored this on my 520SX and lost a cam bearing. I shut it down right away but I still ended up with ball bearings down in my crank case. I had to split the cases to get them all out.

On any used RFS I would replace the cam bearings immediately as you never know how much time/abuse they have seen (not changing the oil/over-reving etc). Beyond that the bikes are pretty much bullet proof and STRONGE in a mild mannered sort of way. Good luck.

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Thanks for the info, I will be sure to keep that in mind. Is the water pump on a 520 on the lower right side of the motor when you sitting on the bike like most japanese smokers?

How involved is the process of changing the cam bearings and the 2 seals?

Do the 520sx's use shims to adjust the cams or is it the screw setup I have heard people say the EXC's use?

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how much am I looking at spending and how much time to replace cam bearings?

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The waterpump is located on the end of the cam shaft at the top of the engine just under the gas tank (shifter side)

It isn't that hard to do but you do have to break the timing chain which requires a special tool. It cost about $50 bucks but works great. The links are a few dollars and the bearing are like $8 bucks each (there are 2). Make sure you get the newer sealed bearings. It sounds a little intimidating but isn't that hard to do. I have a manual that maps it out pretty well. If you decide you need it let me know and I can scan it an e:mail it to you. All The RFSs (not the new 250 SXF) use rocker arms that can be adjusted by simply popping of the caps and using a 10mm box wrench and a screw driver. No shims on these puppies.

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Thanks a lot for the info. Well learning that the valvetrain doesnt use shims makes me happy 🙂

I was wondering if someone could tell me if this is correct? The 520SX was made up until 2002 and then it was replaced by the 525 in 2003. The reason I ask is the 2 520's I have been considering are supposedly '03s?? Did they make 520 in early 03 and then go to the 525 mid year or something? Thanks

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Thanks a lot for the info. Well learning that the valvetrain doesnt use shims makes me happy 🙂

I was wondering if someone could tell me if this is correct? The 520SX was made up until 2002 and then it was replaced by the 525 in 2003. The reason I ask is the 2 520's I have been considering are supposedly '03s?? Did they make 520 in early 03 and then go to the 525 mid year or something? Thanks

No it's not the 520 was made from 00-02 the 525 is '03 and newer There was no mid year changes. If they are infact 520's they are '02's or older. One way to tell is what size is the front axle if it is a 20mm axle then it's a good bet the bike is an 02 or older if it is a 26mm axle then it's an '03 or newer. The olther was you can tell is by the type of carb. The 02's and olderhave the old style FCR carb on them the '03's and newer have the new style FCR carbs

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any performance differences in the new style fcr's and the old ones? if so is it worth swapping the old for the new? thanks

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Does this apply to all KTMs? I'm looking at a '02 400 exc, and haven't started researching any possible issues with these. Changing the cam bearings wouldn't be too much of a problem if I picked it up, peace of mind knowing they're fresh if that's one of the problem areas on KTMs.

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All the RFSs are the same. I believe the problem was worst on the older models before they went to sealed bearings but keeping them fresh is always a good idea and cheap insurance (once you buy the tool and learn the procedure). This is the ONLY engine failure I have had on my 01 520SX and I must have >200 hrs on it. Oh you do have to watch the intake valve adjustment. It is easy to tell when it is getting tight as the bike gets harder to start.

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You can update the cam bearings and associated seals for under $100

Here is a link: Cam Bearings

The first article is a write up I did for the process.

First time it will take you about 3 hours total, I can now do it in under an hour.

The big thing is you need to split the timing chain, it's easy but the KTM tool is $$$ to do it (you can use a generic chain press)

Rod

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On the 2 syles of carbs, the changes are minor, either can run as good. The old one like the pilot jet one size larger. Biggest difference is the new one has the accelerator pump linkage under a cover, the early one was more vulnerabe to water getting in the AC pump where the rod went in.

Past problems, In 01 they got a bad batch of bearings, some failed some survived, many of us got in the hadit of changing bearings once a year just so we could go in to the woods with confidence.

03 a lot of minor changes took place, one of the them head casting was changed, many of us prefer the early one.

03 the SX models got hopped up, bigger carbs, Ti valves on the 450, some had a hotter cam, rev limiter raised, lightened cranks & 4 speed transmissions, the 525SX got different valve spings.

,

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Thanks for all that info Dave. Do you know if the 02 520SX had any issues? Did the 02 have any nice parts like the better head casting or anything?

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Travis,

i am surprised you did not mention the upgrades for the 520? i am referring to the water pump carrier and the screen at on the cam chain side that prevents ball bearings from entering the cases.

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Travis,

i am surprised you did not mention the upgrades for the 520? i am referring to the water pump carrier and the screen at on the cam chain side that prevents ball bearings from entering the cases.

Jon you knuckle head 🙂 the 02's have the upgraded carrier already.

I didn't mention any thing about upgrades because I was trying to help him identify the bike before we start talking upgrades that way we could point him in the right direction.

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Travis, I looked at a nice 02 today that I think I am going to get. So the 02 already has the upgraded water pump carrier and the screen at on the cam chain side that prevents ball bearings from entering the cases that jon talks of?

One thing I did notice on the one today is that the clutch is chattery until you pull it in and put it in gear which I have read is normal is that correct? What causes it to chatter?

I think I want an SX, but I have never ridden a EXC or MXC. Does the wide ratio tranny make a huge difference? How does a WR tranny do on a MX style track/trail?

A MXC is basically just an SX with a headlight, bigger tank, 5th and 6th gear right?

Would adding 5th and 5th gear to an SX make it comparable to an EXC?

Thanks

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All of the 520-525 engines are the same size, something like 510cc.

The cam bearing problem was primarily an 01 issue, the actual bearings KTM bought where poor quality. Other than that 01 issue the cam bearings are good for a couple of seasons use, about the same as the stainless steel valves themselves.

02 had the upgrades in the seal retainer area, the seal itself got improved in 04.

Clutch is chattery, umm yes normal.

Wide ratio trans is the hot deal in the woods, gives you a real low 1st gear, it sucks on a mx track.

MXC basically a SX with tank, lights & 5&6th? Well in 00-01 that would be close, also no Estart and a smaller lighter magneto on SX both of which make the engine more responsive at the expense of traction.

02 the SX got 48mm forks and I beleive bigger axels both of which all models got in 03

03 the SX became a real hot rod, rev limiter was raised abt 1,000 RPM, carb got bigger, intake port got bigger to match, crank got lightened a bunch, valve springs changed, if my memory is corect the spring retainers where aluminum. Suspention was a bit firmer for MX tracks, oh and these also blew up, KTM recalled the rev limiter and the valve springs have proven to be poor design.

04 the cam & rev limiter went back to normal and the crank weight went to somewhere in between 02 & 03 specs, valve springs remain kinda bogus.

05 I can't recal any engine changes from 04

Suspension & chassis improvments have been annual evolution, each year is better.

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I have an 03 525SX. What would be the best upgrade for the valve springs, to make them not such a problem?

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