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Fire Breathing KTM 300

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About a year ago I bought a clean 2007 KTM 300XCW to replace my '95 CR500.  It is a fantastic bike with a bit of suspension tuning and the motor has a strong, broad torque curve.  Obviously the first step is the red exhaust valve spring.  Beyond that, the bike still displayed a bit of a flat spot between the off idle torque and the upper RPM hit.  No more!  Now the mid range is violent. I took some clues form Jeff Slavens website and built my own Mule.  Instead of milling the base of the cylinder, I simply used the thinnest base gasket available, then shaved .035" off the head (piston to head clearance is at .035" after milling).  The difference is night and day.  This is as fast or faster than any of my CR500s (I had five of them) with better manners, less weight and a broader torque curve.  I would not have believed it had I not done it myself.  If you want your 300 to fly, this is the way.

Edited by Lehiguy
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I have the thinnest base gasket in mine and had slavens mill the head. Not impressed &%$#@! is wrong with mine

don't worry bout it. I have had 2 different 300s and both had this and several other performance mods, yet neither could ever compare to any CR500. And I'd bet money his wont touch a cr either

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I had my 06' 300's cylinder decked and the head shaved by Jeff a few weeks back.  Also used his jetting kit and put in the red PV spring (I was using the yellow before).

 

All that made a big difference, but it's still feels slow until the PV opens, at least up here in the mountains in the thin air.

 

I keep thinking about a Service Honda.  Should be a lot faster than a 300 right? :confused:

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About a year ago I bought a clean 2007 KTM 300XCW to replace my '95 CR500.  It is a fantastic bike with a bit of suspension tuning and the motor has a strong, broad torque curve.  Obviously the first step is the red exhaust valve spring.  Beyond that, the bike still displayed a bit of a flat spot between the off idle torque and the upper RPM hit.  No more!  Now the mid range is violent. I took some clues form Jeff Slavens website and built my own Mule.  Instead of milling the base of the cylinder, I simply used the thinnest base gasket available, then shaved .035" off the head (piston to head clearance is at .035" after milling).  The difference is night and day.  This is as fast or faster than any of my CR500s (I had five of them) with better manners, less weight and a broader torque curve.  I would not have believed it had I not done it myself.  If you want your 300 to fly, this is the way.

 

You are in the 4 stroke section just in case you didn't see.. You might get more results in the KTM 2 stroke section.. but you are getting traction anyway...but put another post in the 2 stroke side where more guys have what you have. More info the merrier..

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You are in the 4 stroke section just in case you didn't see.. You might get more results in the KTM 2 stroke section.. but you are getting traction anyway...but put another post in the 2 stroke side where more guys have what you have. More info the merrier..

Somebody moved me.  I don't know how to fix it.

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don't worry bout it. I have had 2 different 300s and both had this and several other performance mods, yet neither could ever compare to any CR500. And I'd bet money his wont touch a cr either

I don't blame you for being a skeptic, I have owned five CR500s and would not believe it either if I had not built and ridden this thing myself.  It is insanely fast.  Add the freaky good turning and brakes and you can get down trails at speeds that the CRs only dreamed of. 

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I have the thinnest base gasket in mine and had slavens mill the head. Not impressed &%$#@! is wrong with mine

Everything has to be just right.  I used the recommended jetting, a ProCircuit pipe, I cut three inches of the silencer and used a fresh Wiseco piston with the head mod.  I rode it again today and it freaks me out how much stronger it is then when I bought it.  I can carry the front end over anything and keep it up as long as I want.  That alone makes riding better for me, I am used to CR500s where obstacles are overcome with throttle.

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Everything has to be just right.  I used the recommended jetting, a ProCircuit pipe, I cut three inches of the silencer and used a fresh Wiseco piston with the head mod.  I rode it again today and it freaks me out how much stronger it is then when I bought it.  I can carry the front end over anything and keep it up as long as I want.  That alone makes riding better for me, I am used to CR500s where obstacles are overcome with throttle.

 

 

Whose recommended jetting? KTM manual?

 

I think my biggest problem is my pipe was too smashed. New one on the way.

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Whose recommended jetting? KTM manual?

 

I think my biggest problem is my pipe was too smashed. New one on the way.

Yup.  They are pretty good at correct jetting recommendations.  The PO had used a JD needle, ran, but not great.  The KTM recommended needle really helped.  One thing that is critical is the exhaust valve.  Make sure to set the "Z" dimension and make sure it has full range of motion.

Edited by Lehiguy
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Yup.  They are pretty good at correct jetting recommendations.  The PO had used a JD needle, ran, but not great.  The KTM recommended needle really helped.

 

 

Right on. I never touch jetting but sounds like I should.

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Yup.  They are pretty good at correct jetting recommendations.  The PO had used a JD needle, ran, but not great.  The KTM recommended needle really helped.  One thing that is critical is the exhaust valve.  Make sure to set the "Z" dimension and make sure it has full range of motion.

Typically, the outer adjustment of the exhaust valve should be flush with the housing.

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don't worry bout it. I have had 2 different 300s and both had this and several other performance mods, yet neither could ever compare to any CR500. And I'd bet money his wont touch a cr either

 

I've owned a CR 500, and the KTM can run with the CR only with better than stock setup.  Red power valve spring, FMF Fatty pipe, Powercore silencer, it runs so damn strong on top that I would argue it'll hang with a 500.

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Did same thing with my cr250. You change the power curve a lot and broadens the power delivery. My problem is I kept shattering cranks. I would race the bike and it would last 1.5 seasons then eat itself. I'm sure the ktm crank more beefier.

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I've owned a CR 500, and the KTM can run with the CR only with better than stock setup. Red power valve spring, FMF Fatty pipe, Powercore silencer, it runs so damn strong on top that I would argue it'll hang with a 500.

Not if you hav traction

My kx5 will eat all my bikes in a drag, my ktm 520 would hold it own cause it has 6th gear and will climb linearly to over 100.

I'm curios about the modfied ktm300, probably great mod.

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I own a couple of KTM's although not a 300. I do own a KTM250SX which might be close enough. The KTM's do a lot of stuff better but faster than my SH KX500AF in straight line performance? No, not even close. It's like an NHRA Super Stock car going up against a Funny Car or Top Fuel. I wish KTM would make a true big bore two stroke again! Check my signature line to see what I'm comparing against.

Edited by rmzpegger
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Not if you hav traction

My kx5 will eat all my bikes in a drag, my ktm 520 would hold it own cause it has 6th gear and will climb linearly to over 100.

I'm curios about the modfied ktm300, probably great mod.

In a steep upgrade with silty sand like Lucerne Valley in SoCal, the 500 will outpull the 300.. but for handling and all, no question the 300 is a more competitive machine. For Glamis I'd take the 500 but not for much else.

Keep in mind that I owned and loved my CR 500 from 04 to 07, but the newer bikes handle sooo much better. The technology has advanced greatly in 25 years since the last 500 mods were put into production

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stock 500 aint that impressive. good running 300 should hang pretty close. 500 has more torq but both bikes are about the same hp. 300 alot lighter

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