KTM 450 Piston size

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2/5/2018 1:57 PM

About to order my parts to do top end on my 2016 KTM 450 sxf FE
I am,going with OEM parts. They have 2 sizes listed
Do I need to measure first? Was hoping to order and have on hand so I can knock it out one evening.
Thanks for the help guys.

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2/5/2018 5:04 PM

Size 1 or size 2?

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2/5/2018 5:04 PM

seawitch wrote:

About to order my parts to do top end on my 2016 KTM 450 sxf FE
I am,going with OEM parts. They have 2 sizes listed
Do I need to measure first? Was hoping to order and have on hand so I can knock it out one evening.
Thanks for the help guys.

Look on the top of the cam chain tensioner housing of your cylinder. You should see "I or II" stamped there. Order based on that stamped numeral.

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2/6/2018 4:35 AM

Thanks so much!

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2/6/2018 5:05 AM

How many hours? If more than 75h you should get it measured for sure. If you have a type 2, then my guess is you need a C-piston.

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2/6/2018 5:20 AM

I did not see any stamped I or II
I have 106 hours. Most I have ever gone before rebuild on any motor. Just life is busy. Plus been riding alot. On a positive note I am a every two track day oil and air filter changer and I usually ride in a higher gear.
I think KTM only offers I and II size pistons?

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2/6/2018 5:40 AM

seawitch wrote:

I did not see any stamped I or II
I have 106 hours. Most I have ever gone before rebuild on any motor. Just life is busy. Plus been riding alot. On a positive note I am a every two track day oil and air filter changer and I usually ride in a higher gear.
I think KTM only offers I and II size pistons?

I would for sure measure the cylinder. I was at a C-piston at 100h+ on my 2013 SXF. Measure the cylinder and you dont have to worry about it being 1 or 2.

Vertex and Prox has C (cast). Wiseco has only one size if i remember correctly (forged type). I prefer forged all day long, but at certain wear-limits you have to go with cast or find a size+ forged.

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2/6/2018 5:48 AM

Ok Looks like a next monday evening project then! Dont want to miss out on a full weekend!
I ordered a CD rom manual also.
Thanks for the help guys. Cant stand the lack of service manual you get with these bikes!
After years of yamahas I got spoiled I suppose.

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2/6/2018 7:29 AM

seawitch wrote:

Ok Looks like a next monday evening project then! Dont want to miss out on a full weekend!
I ordered a CD rom manual also.
Thanks for the help guys. Cant stand the lack of service manual you get with these bikes!
After years of yamahas I got spoiled I suppose.

Hey man let us know what are you going to do wink

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2/6/2018 12:06 PM

seawitch wrote:

Ok Looks like a next monday evening project then! Dont want to miss out on a full weekend!
I ordered a CD rom manual also.
Thanks for the help guys. Cant stand the lack of service manual you get with these bikes!
After years of yamahas I got spoiled I suppose.

You have all the tools, cylinder indicator + even more important a tool to calibrate it with? Otherwise i would take it to a detailed mechanical shop smile $30-50 or what ever and it is done.

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2/6/2018 12:28 PM

I do not have a dedicated cylinder indicator, no sir.
I do have some nice dial calipers and what not. Figure I can get a good measurement using a piston ring...
Have split many a motorcycle case and can build or rebuild pretty much anything from mx bikes to boats to heavy equipment. The Lord blessed me with a mechanical mind.
Just asking about piston size because I am OCD.

Still kills me not to have a service MANUAL. I will have to print out my CD I have on way.

Thanks for the help.

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2/6/2018 12:45 PM

seawitch wrote:

I do not have a dedicated cylinder indicator, no sir.
I do have some nice dial calipers and what not. Figure I can get a good measurement using a piston ring...
Have split many a motorcycle case and can build or rebuild pretty much anything from mx bikes to boats to heavy equipment. The Lord blessed me with a mechanical mind.
Just asking about piston size because I am OCD.

Still kills me not to have a service MANUAL. I will have to print out my CD I have on way.

Thanks for the help.

Dial calipers you can forget about. We are talking about measuring 0.01mm segments in 3 difference heights/places down in the cylinder.

Here are the values you need to calibrate from, or use as reference for cylinder indicator:

Ok mounting Clearance: 0.040 - 0.082
Cylinder (Size 1) 95.00 - 95.012
Cylinder (size 2) 95.013 - 95.025

My measures for my 450 SXF 2017 was now at 111h:
Top: 95.012> 95.022v
Midd: 95.022> 95.022v
Bottom: 95.032> 95.017v

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2/8/2018 9:37 AM

seawitch wrote:

About to order my parts to do top end on my 2016 KTM 450 sxf FE
I am,going with OEM parts. They have 2 sizes listed
Do I need to measure first? Was hoping to order and have on hand so I can knock it out one evening.
Thanks for the help guys.

atrdrvr7 wrote:

Look on the top of the cam chain tensioner housing of your cylinder. You should see "I or II" stamped there. Order based on that stamped numeral.

This is incorrect. I thought the same. According to dealership for a rebuild you order the II even if you have the I stamped. The pistons are so close in size.

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2/8/2018 1:17 PM

seawitch wrote:

About to order my parts to do top end on my 2016 KTM 450 sxf FE
I am,going with OEM parts. They have 2 sizes listed
Do I need to measure first? Was hoping to order and have on hand so I can knock it out one evening.
Thanks for the help guys.

atrdrvr7 wrote:

Look on the top of the cam chain tensioner housing of your cylinder. You should see "I or II" stamped there. Order based on that stamped numeral.

RCMXracing wrote:

This is incorrect. I thought the same. According to dealership for a rebuild you order the II even if you have the I stamped. The pistons are so close in size.

No, you measure your cylinder and take a piston that fits. If they are so close and it does not matter, they could have had one size. Instead there is at least 3 sizes on the market. You get piston slap with a to big piston.

For most people a 2 would go at first rebuild, but you could easily be up for a C/3 depending on amount of hours and wear.

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2/8/2018 2:22 PM
Edited Date/Time: 2/8/2018 2:27 PM

atrdrvr7 wrote:

Look on the top of the cam chain tensioner housing of your cylinder. You should see "I or II" stamped there. Order based on that stamped numeral.

RCMXracing wrote:

This is incorrect. I thought the same. According to dealership for a rebuild you order the II even if you have the I stamped. The pistons are so close in size.

aees wrote:

No, you measure your cylinder and take a piston that fits. If they are so close and it does not matter, they could have had one size. Instead there is at least 3 sizes on the market. You get piston slap with a to big piston.

For most people a 2 would go at first rebuild, but you could easily be up for a C/3 depending on amount of hours and wear.

KTM only dealership, been around forever. It wasn’t even a discussion when I ordered. The quote was, “The difference is breathing on your caliper.” I thought it was strange and figured I should be getting a I (1)...that’s what’s stamped, but they were like, nope, ordering you a II (2). They also added that I would be surprised how much room there was in the bore. Agree the right way would be to be methodical about it, precise measurements, etc. Guess I’ll find out when it’s tore down.

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2/8/2018 5:23 PM

RCMXracing wrote:

This is incorrect. I thought the same. According to dealership for a rebuild you order the II even if you have the I stamped. The pistons are so close in size.

aees wrote:

No, you measure your cylinder and take a piston that fits. If they are so close and it does not matter, they could have had one size. Instead there is at least 3 sizes on the market. You get piston slap with a to big piston.

For most people a 2 would go at first rebuild, but you could easily be up for a C/3 depending on amount of hours and wear.

RCMXracing wrote:

KTM only dealership, been around forever. It wasn’t even a discussion when I ordered. The quote was, “The difference is breathing on your caliper.” I thought it was strange and figured I should be getting a I (1)...that’s what’s stamped, but they were like, nope, ordering you a II (2). They also added that I would be surprised how much room there was in the bore. Agree the right way would be to be methodical about it, precise measurements, etc. Guess I’ll find out when it’s tore down.

I had the "I" stamped on mine. My Mechanic measured also and it was the correct size. Bike has been perfect for the last 25hrs.

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2/8/2018 10:47 PM

Hopefully my manual will arrive soon. I will base my piston size purchase on manual recommendations. Seems to be some conflicting ideas. One thing thats driving me crazy is WHERE IS MY SIZE STAMP!
I may see it but dang its def not obvious. Thanks for the replies.

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2/10/2018 9:59 AM

Photo

Photo

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Take it to the limit, one more time!

2/10/2018 10:00 AM
Edited Date/Time: 2/10/2018 10:03 AM

The bottom picture is where you will find the size I or II. Also you can see from the spec, they are only approx. 0.0005 inch difference in the two pistons.

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Take it to the limit, one more time!

2/10/2018 11:10 AM

mx317 wrote:

The bottom picture is where you will find the size I or II. Also you can see from the spec, they are only approx. 0.0005 inch difference in the two pistons.

The pistons can differ 0.03mm.
Cylinder 1 or 2 differs up to 0.12mm within each model, which is why it is important to measure the cylinder. If you take the smallest 1 compared to biggest 2 it is 0.25mm which is quiet a big difference as your picture states smile

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2/10/2018 1:12 PM

mx317 wrote:

The bottom picture is where you will find the size I or II. Also you can see from the spec, they are only approx. 0.0005 inch difference in the two pistons.

aees wrote:

The pistons can differ 0.03mm.
Cylinder 1 or 2 differs up to 0.12mm within each model, which is why it is important to measure the cylinder. If you take the smallest 1 compared to biggest 2 it is 0.25mm which is quiet a big difference as your picture states smile

No it's not 0.25mm, that's 0.010 inches difference. There is only 0.001 inches if you went to the very bottom of the tolerance to the end of tolerance on the cylinder, not the piston. There is 0.0005 inches (or 0.013mm) between the piston sizes.

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Take it to the limit, one more time!

2/10/2018 1:16 PM

I agree he needs to measure the cylinder to check for wear with a dial bore gauge.

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Take it to the limit, one more time!

2/11/2018 5:52 AM

Riding today
Tear down tomorrow eve
Then measure bore
Hopefully 3 days to get parts
Then,back up and going by weekend

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