525 engine thoughts

I've seen a lot of posts about converting sx transmissions to 6 speeds but what are the possibilities of installing sx cranks and flywheels into exc or mxc cases? Not that I'm thinking about doing this to my new bike, but when rebuild time comes. A 41mm carb and big bore kit would be nice additions at that time too. Does the 570 kit require an aftermarket crank? Just thinking out loud here. :cry:

You can get all the parts from your ktm dealer all factory ktm parts

The 570 kit will come with a KTM stroker crank (74mm) and a big bore cylinder/piston (97mm)

So is the stroker crank considered a lightweight sx crank or the heavier exc/mxc crank?

The stroker crank is a full circle type like the EXC.

How does the 570 kit feel, power wise, compared to a LC4 640. How well does this motor hold up to this mod. Any body?

You can also do a 99mm piston "570 kit" without changing the crank. It's much easier since you don't have to split the cases. Plus it will rev faster than the factory stroker crank and 97mm piston.

Travis do you have any idea what the compression is of the piston kit you describe? Or if there is a 12.5:1 available for that size or the 540 for that matter? Also do you know if this works in conjunction with a cam modification like the hotcam? I remember reading somewhere somebody was unhappy with their big bore kit (can't remember exactly what it was) because it would not rev past a certain point. I'm pretty sure it was on ktmtalk but not positive.

The compression for the 570 kit (99mm) is 11.5:1 There is no other piston avalible in the 99mm bore. For the 540 (97mm) ther are 2 compression ranges avalible 11:1 and 12.5:1.

The stock cam causes the motor to feel a little flat on top when used with the bigger pistons. The 8/06 cam is a good choice for the 570 or the 540 with stock compression.

The HotCam will really makes these kits scream up top end they will feel soft on the bottom. The Hot Cam is a better choice for a hi compression motor because the higher compression piston will offset the bottom end loss caused but the cam

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Similar Content

    • By Ponch
      I have a 2007 450 EXC that I recently installed a new clutch slave cylinder on. Per the 2007 KTM service manual it clearly states that the clutch needs to be filled with hydraulic oil, which I did (magura blood). That was yesterday. I went out to double check the level today and when I removed the cover, the rubber seal was all contorted and out of shape. I then looked at the cover and it's a Brembo clutch and says "DOT 4 brake fluid only".
      I flushed the line and the master cylinder about 7 times with DOT 4 brake fluid and there was no sign of the magura blood left in the system. My question is: other than the rubber boot on the master cylinder, what damage might have been done by putting in the hydraulic oil? It was in for about 24 hours.
      Thanks in advance for any advice!
    • By pumpernickelBrad
      Hi Folks!

      Sorry if there are a bunch of threads already but I used the site's search function and didn't find anything so far...

      I just found a decent deal on a '14 350 EXC-F with 11k km (unknown hours). Has a few goodies including skid plate, hand guards and it's for sale for about $2k CAD less than a '16 with 6k km on it.
      The bike is in showroom condition (appearance) with no indication it has been offroad at all.

      What would be the gotchas that would make this deal realistic? I'm coming from a WR250R where the engine lasts forever, is 11k street kms high for these bikes? 
      Are there any big defects in the '14s that I haven't dug up yet?
      With no service records what things should be done, checked, etc?
    • By Brannnt
      I purchased an '06 525 EXC some time ago, and recently pulled the motor out of the frame to address some other issues. When I removed the clutch slave cylinder, I noticed an issue the previous owner neglected to tell me about during the purchase.
      It appears that at some point, the chain broke and damaged the engine case near the clutch slave cylinder (see pics, please). I have noticed that the clutch does not fully disengage (bike lurches a bit going into gear, neutral is hard to find... its worse when engine is cold) ... I did not notice any leaks around this area (mineral oil or engine oil) before or during disassembly. 
      The previous owner (or someone) repaired it with some sort of epoxy.
      Without doing my due diligence (checking clutch fluid level, bleeding) I hesitate to state that this is the cause of my clutch disengagement issue ... but pardon my ignorance here and help me out: How bad is this?  Am I looking at replacing my engine case here or is the previous owner's jerry rig good enough?

    • By Black Sox
      Just bought a new 2017 350 excf ,will be doing 98% off road ,ordered skid plate bark busters ,
      my ? Is what's the best easiest way to eliminate rear fender light assembly.I still would like to have a break light.
      xcf fender will fit so dealer says,under $50.00 👍But xcf brake light $125.00 .👎What's the best economical way of doing this?
    • By JNV
      Hi friends from Spain.
      Mi new KTM