How does my top end look? KTM 350 SXF 2020

mx4all
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mx4all
Edited Date/Time 6/19/2022 9:22pm
About to put a new piston in my bike. The bike has 70h on it and the piston 45h.
I am not an engine expert so would like your input.
Does the cylinder look ok or is it worn out?
And what about the valves?

I might bring the top end Down to my local shop so they can take a look at it..







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FGR01
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FGR01 6/11/2022 11:14am
6/11/2022 11:14am
The wear on the cylinder wall and piston skirt looks kind of concerning. What oil are you running?

If it was me, I'd recoat or replace the cylinder and new piston and get the head resurfaced and valve seal checked.

Has any dirt ever got past the filter? What filter oil are you running?

I'd also check the oil pump gears while you're in there and consider replacing with new ones or aluminum aftermarket ones.
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Broseph
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Broseph 6/11/2022 12:47pm
6/11/2022 12:47pm
mx4all wrote:
About to put a new piston in my bike. The bike has 70h on it and the piston 45h. I am not an engine expert so...
About to put a new piston in my bike. The bike has 70h on it and the piston 45h.
I am not an engine expert so would like your input.
Does the cylinder look ok or is it worn out?
And what about the valves?

I might bring the top end Down to my local shop so they can take a look at it..







What brand of piston is that? 45hrs on it you say? Yeah the skirt wear looks like a bit much. Kind of reminds me of how a Wiseco-made ProX piston wears.
CarlinoJoeVideo
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CarlinoJoeVideo 6/11/2022 7:22pm
6/11/2022 7:22pm
Dang I have 125 hours on my 350 never even checked the valves.

I agree, if you have the bike apart, might as well take care of that wear on cylinder and piston.
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FGR01
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FGR01 6/11/2022 7:30pm
6/11/2022 7:30pm
Also, I wonder if some riding habit could be causing that cylinder wear. Like doing massive air revs and then landing with the throttle wide open, or downshifting in the air causing a big rpm spike when you land. Both of these examples could send a big driveline shock back into the engine and quickly snatch the rod and piston.

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mx4all
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mx4all 6/12/2022 4:44am
6/12/2022 4:44am
Hello guys.

I bought the bike recently and only done one practice on it. I thought it smooked a little bit more than normal when cold and it also looked like the head gasket didnt seal 100%. It was a little bit oily after riding so thats why I decided to put a new piston in and check the cylinder/valves.

I did send the pics to my local shop mecanic and he said it looked like normal used engine but its Hard to tell from pics he said so I Will bring it to him next week so he can check.
Leeham
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Leeham 6/12/2022 8:37pm
6/12/2022 8:37pm
FGR01 wrote:
Also, I wonder if some riding habit could be causing that cylinder wear. Like doing massive air revs and then landing with the throttle wide open...
Also, I wonder if some riding habit could be causing that cylinder wear. Like doing massive air revs and then landing with the throttle wide open, or downshifting in the air causing a big rpm spike when you land. Both of these examples could send a big driveline shock back into the engine and quickly snatch the rod and piston.
I put 51 hours on my YZ250F, I do rev it everywhere including the air and land with heavy throttle. I had zero skirt and cylinder wear to my surprise, engine looked new! Maybe that piston that got put in was not a good fit allowing skirt wear.

70 hours on the cylinder and its already getting a 3rd piston? What happened to the first one? Why only 25 hours? I know its second owner but still.

My .02, get it replated and matched with an OEM piston. Check valve clearances, if good, leave them alone. Out of spec, shim and check it again in the next 3-5 hours for difference.
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katoom350
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katoom350 6/15/2022 7:52pm
6/15/2022 7:52pm
That looks like a lot of wear for the amount of hours for sure
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Hcallz5
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Hcallz5 6/16/2022 5:15pm
6/16/2022 5:15pm
What kinda oil do you use? I've got 50 hours on my 350 and now I'm paranoid.
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183Matt
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183Matt 6/19/2022 9:22pm
6/19/2022 9:22pm
Hcallz5 wrote:
What kinda oil do you use? I've got 50 hours on my 350 and now I'm paranoid.
Your 350 motor will last a long t8me with proper care and maintenance. Most trail riders I know with 350’s are getting 150-200 hours out of their top ends.
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JCMX421
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JCMX421 8/8/2023 2:06pm
8/8/2023 2:06pm
Hcallz5 wrote:
What kinda oil do you use? I've got 50 hours on my 350 and now I'm paranoid.
183Matt wrote:
Your 350 motor will last a long t8me with proper care and maintenance. Most trail riders I know with 350’s are getting 150-200 hours out of...
Your 350 motor will last a long t8me with proper care and maintenance. Most trail riders I know with 350’s are getting 150-200 hours out of their top ends.

I have a 17 350 with 120 hours, valves haven’t been touched still in spec, no rebuilds runs perfect. The 350s just built different lol

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