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How many hours out of a 2010-2014 KTM 250Sx?

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How many hours would you do a top end rebuild on your KTM Sx if they are in the year range 2010 to 2014. What do you change? The whole head? Pistons? Top End bearing? Just rings?

I was thinking about every 50 hours of hard trail riding. I'm 18 and I ride pretty hard. I specified my age because older or younger people ride differently to my style.

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Maintenance level and how the bike is ridden also have a large factor. I plan on a top end around 80-100 hours on my 300XC.

When I do rebuild the top it will get new piston, rings, wrist pin, clips, and gaskets. Clean the power valve and check tolerances on everything not being replaced like rod play and cylinder. That's the plan anyway.

Edited by hezzdown
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Exactly what hezz said above, especially if your jetting is "on", you run a good synthetic at 45:1 and clean/change filter at least every 3rd ride. I can tell its time when the bike starts to have a little less power and gets harder to start. This can mean other probs too but its a good sign that its time to do a top end. And while u have the cylinder off its not a bad idea to ask a shop to run the honing tool thru it quick.

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I would argue the filter to be changed EVERY RIDE.  It's amazing how much dirt debris and sediment comes out of the filter everytime I clean it, after each ride.  In the opinion of my mechanic (an experienced local pro), the air filter is the MOST IMPORTANT maintenance item from ride to ride.  He has seen pistons last less than half as long because the air filter wasn't kept clean.

 

My 300 piston goes 125 hours of riding.  On a 250, revved up a lot, I would go prolly 80 - 100 hrs.  Always get the Vertex pistons, they are OEM and the best on the market.

 

Last weekend I did a two day race in west Texas.  Saturday I raced 30 miles, then I cleaned the air filter so I had two fresh filters for the 75 miles on Sunday.  After the first 30 miles on Sunday I swapped it out at a gas stop (enduro formats are awesome).  But a AA racer on my line has a 450 SX, brand new.  His bike started to chug up and stall after 50 miles of riding, his air filter wasn't breathing.  He told me that the stalling issue was a precursor to injectors clogging.  Next time I bet he'll be swapping filters too.

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I would argue the filter to be changed EVERY RIDE.  It's amazing how much dirt debris and sediment comes out of the filter everytime I clean it, after each ride.  In the opinion of my mechanic (an experienced local pro), the air filter is the MOST IMPORTANT maintenance item from ride to ride.  He has seen pistons last less than half as long because the air filter wasn't kept clean.

I agree, thats why I said minimum of every 3rd ride . You know how many people let that go for months ?  Even people that know this get lazy and wont do it every ride.

I just got 55 hrs of hard racing and training ON MY 125 . I clean the filter, run 32:1 full synth, I jet for summer/winter, I run AvGas . A little maint goes a long way.

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I can share my recent experience replacing first top end on my 07 250SX at 115 hours. I ride combination of desert, trail, mountain, and novice/intermediate class mx. Cleaned air filter after every ride, run Motorex 50:1, and have the jetting dialed for my mostly sea-level conditions.

 

It still had such high compression that I didn't need to do it for that reason, but started wondering about part fatigue. It was still running sweet. I recently had a bad seal on the filter for a day and sucked some dirt at the track, that made my decision easy. It's torn down now.

 

 

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How many hours would you do a top end rebuild on your KTM Sx if they are in the year range 2010 to 2014. What do you change? The whole head? Pistons? Top End bearing? Just rings?

I was thinking about every 50 hours of hard trail riding. I'm 18 and I ride pretty hard. I specified my age because older or younger people ride differently to my style.

on my 13 I don't wait any longer than 60hr to change the piston (I race so my bike gets a lot of stress)

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I agree with Loving offroad pain, I rebuilt my 2012 300 XCW at 120 hr and I always use KTM parts, I replaced piston, rings, wrist pin and keepers. Buy the piston keepers from Slavens Racing, he has a special set that are so much easier to install. My rings didn't even have a sharp edge on them and everything looked good, make sure you use quality two stroke oil, Motorex and Silkolene are a couple I have had good results with mixing at 50:1

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I would argue the filter to be changed EVERY RIDE.  It's amazing how much dirt debris and sediment comes out of the filter everytime I clean it, after each ride.  In the opinion of my mechanic (an experienced local pro), the air filter is the MOST IMPORTANT maintenance item from ride to ride.  He has seen pistons last less than half as long because the air filter wasn't kept clean.

Hmm, yeah, I never thought about maintaining the filter soo much. It makes sense though. How do you clean yours? Water? Hose the shit out of it? Do you use special products?

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Hmm, yeah, I never thought about maintaining the filter soo much. It makes sense though. How do you clean yours? Water? Hose the shit out of it? Do you use special products?

 

You will find a lot of arguments on both sides, I use solvents.  If the paint thinner isn't harsh enough to remove the sediments and crap, I use gasoline.  Your filter won't last as long using gas, just replace it for $30 every year or two.  Much easier than messing with No Toil systems or whatever.

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Hmm, yeah, I never thought about maintaining the filter soo much. It makes sense though. How do you clean yours? Water? Hose the shit out of it? Do you use special products?

 

But use nitrate rubber gloves.  They hold up to the gasoline protecting ur hands.. you don't wanna get leukemia from soaking ur hands in solvents for years on end, that happened to my buddy.  Luckily he kicked it.

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But use nitrate rubber gloves.  They hold up to the gasoline protecting ur hands.. you don't wanna get leukemia from soaking ur hands in solvents for years on end, that happened to my buddy.  Luckily he kicked it.

All this time I was using bare hands to clean carbs. I knew it was bad but never researched into it. Lukemia sounds bad!. I will purchase some gloves :) Thanks .

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All this time I was using bare hands to clean carbs. I knew it was bad but never researched into it. Lukemia sounds bad!. I will purchase some gloves :) Thanks .

 

They are cheap, $10.00 for 100 disposable gloves at Harbor Freight.  Again though buy the nitrate ones.  Regular latex gloves will fall apart instantly in solvents.

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so guys i am picking up a 2012 200 exc with 40.5 hours on it. the previous owner just went on trail rides with it as it was just his leisure bike. how long do you think a piston will last before i need to replace it????

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