Weird engine noise 2019 sx250

Cammy41
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Cammy41
Edited Date/Time 10/19/2021 1:07pm
Anybody any ideas?
Strange rattling noise after pulling it out of the van last weekend the kickstarter was solid so i rocked the bike in gear and it freed up
After that i did 3 laps and it seemed fine
After starting it to go out again this noise started
Bike rides perfectly ive done a piston 2 hours ago and replaced the starter gear, small end bearing twice, and clutch dampners but its made no difference
Also checked the piston for marks, the bottom end for play and balancer shaft but it seems fine
Bike has a pro circuit system, boyesen rad valve and keihin pwk36 carb
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walent215
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walent215 7/25/2021 8:37am
7/25/2021 8:37am
I would revisit the areas you just recently worked on and be sure all is tight...
clutch and starter gears issues may be surfacing ....
Did you loctite clutch basket nut ?
Any other snap rings or nuts you had to remove for the starter gear?
Primary drive bolt been loctited?
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Cammy41
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Cammy41 7/25/2021 9:27am
7/25/2021 9:27am
All been checked, the starter gear bearing did have a little play and was replaced but never cured the problem
harescrambled
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harescrambled 7/25/2021 9:47am
7/25/2021 9:47am
Cammy41 wrote:
Anybody any ideas? Strange rattling noise after pulling it out of the van last weekend the kickstarter was solid so i rocked the bike in gear...
Anybody any ideas?
Strange rattling noise after pulling it out of the van last weekend the kickstarter was solid so i rocked the bike in gear and it freed up
After that i did 3 laps and it seemed fine
After starting it to go out again this noise started
Bike rides perfectly ive done a piston 2 hours ago and replaced the starter gear, small end bearing twice, and clutch dampners but its made no difference
Also checked the piston for marks, the bottom end for play and balancer shaft but it seems fine
Bike has a pro circuit system, boyesen rad valve and keihin pwk36 carb
Did you check for broken/loose pipe mounts or broken/sacked out/unhooked exhaust retainer springs? If the exhaust is moving around you might hear some rattling.
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Cammy41
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Cammy41 7/25/2021 11:35am
7/25/2021 11:35am
Beginning to wonder if there is another bearing gone bad somewhere
walent215
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walent215 7/25/2021 2:31pm
7/25/2021 2:31pm
You say it’s intermittent and it locked Kickstarter
Transmission gear or clutch related possibly?
Hard to diagnose over a video etc.
I hope you get it nailed down though bud!
Cammy41
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Cammy41 7/25/2021 2:42pm
7/25/2021 2:42pm
I initially thought it was the kickstart gear bearing which i replaced, it wasnt though unfortunately
The clutch seems fine i fitted a new basket along with new rubber dampners aswell
The clutch pates were new at the same time as the piston
Maybe i should just admit defeat and take it to the dealers only thing is its a 6hour round trip
JWACK
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JWACK 7/25/2021 6:02pm
7/25/2021 6:02pm
I had a strange rattle on my 19 250sx that I was sure was an engine noise. It ended up being the front brake lever.
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chump6784
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chump6784 7/26/2021 1:38am
7/26/2021 1:38am
Did you check cylinder to piston clearance when you did the top end? If you slowly start to increase the revs does the sound reduce and eventually stop as the revs get higher? If so it could be the piston is too small for the cylinder. I recently had a "C" size piston turn up that was smaller than the "B" size piston I took out of my son's 65, and when I say smaller it was noticeably smaller. That was from pro X but I was talking to another guy who had the same issue with a vertex piston too
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Cammy41
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Cammy41 7/26/2021 10:45am
7/26/2021 10:45am
chump6784 wrote:
Did you check cylinder to piston clearance when you did the top end? If you slowly start to increase the revs does the sound reduce and...
Did you check cylinder to piston clearance when you did the top end? If you slowly start to increase the revs does the sound reduce and eventually stop as the revs get higher? If so it could be the piston is too small for the cylinder. I recently had a "C" size piston turn up that was smaller than the "B" size piston I took out of my son's 65, and when I say smaller it was noticeably smaller. That was from pro X but I was talking to another guy who had the same issue with a vertex piston too
It was a vertex b piston i removed it wasnt showing any problems but had done 25hours so i replaced it with another vertex b piston
Maybe i should refit it and see if the noise goes away
Cammy41
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Cammy41 7/30/2021 1:56pm
7/30/2021 1:56pm
So i fitted the previous piston and it made no difference
Measured the side to side play in the conrod it came out at 0.75, have i just found the problem?

FGR01
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FGR01 7/31/2021 8:54pm
7/31/2021 8:54pm
What is the service spec for the rod axial play that you are measuring?

That noise sounds like a bad rod bearing or main bearing to me. Has the bottom end ever been apart? How many hours on it?
Cammy41
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Cammy41 8/1/2021 2:46am
8/1/2021 2:46am
FGR01 wrote:
What is the service spec for the rod axial play that you are measuring? That noise sounds like a bad rod bearing or main bearing to...
What is the service spec for the rod axial play that you are measuring?

That noise sounds like a bad rod bearing or main bearing to me. Has the bottom end ever been apart? How many hours on it?
73 hours on it bottom end has never been apart, i dont know i cant find the spec in the manual
walent215
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walent215 8/1/2021 6:37am
8/1/2021 6:37am Edited Date/Time 8/1/2021 6:37am
Cammy41 wrote:
So i fitted the previous piston and it made no difference Measured the side to side play in the conrod it came out at 0.75, have...
So i fitted the previous piston and it made no difference
Measured the side to side play in the conrod it came out at 0.75, have i just found the problem?

Not necessarily
Find out the big end side clearance service limit and go from there
FGR01
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FGR01 8/1/2021 7:01am
8/1/2021 7:01am
FGR01 wrote:
What is the service spec for the rod axial play that you are measuring? That noise sounds like a bad rod bearing or main bearing to...
What is the service spec for the rod axial play that you are measuring?

That noise sounds like a bad rod bearing or main bearing to me. Has the bottom end ever been apart? How many hours on it?
Cammy41 wrote:
73 hours on it bottom end has never been apart, i dont know i cant find the spec in the manual
I don't have the 250 manual, but 0.75mm is the upper limit of the spec (0.45 - 0.75mm) for the 125/150. I'd assume the 250/300 is same or close. Is there any up/down play perceptible in the rod bearing? Do the rod and crank spin free, smooth, and tight by hand? That really sounds like lower rod bearing or main bearing noise to me.
Cammy41
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Cammy41 8/1/2021 7:51am
8/1/2021 7:51am
FGR01 wrote:
What is the service spec for the rod axial play that you are measuring? That noise sounds like a bad rod bearing or main bearing to...
What is the service spec for the rod axial play that you are measuring?

That noise sounds like a bad rod bearing or main bearing to me. Has the bottom end ever been apart? How many hours on it?
Cammy41 wrote:
73 hours on it bottom end has never been apart, i dont know i cant find the spec in the manual
FGR01 wrote:
I don't have the 250 manual, but 0.75mm is the upper limit of the spec (0.45 - 0.75mm) for the 125/150. I'd assume the 250/300 is...
I don't have the 250 manual, but 0.75mm is the upper limit of the spec (0.45 - 0.75mm) for the 125/150. I'd assume the 250/300 is same or close. Is there any up/down play perceptible in the rod bearing? Do the rod and crank spin free, smooth, and tight by hand? That really sounds like lower rod bearing or main bearing noise to me.
No up and down play atall, everything turns freely
Never split lower cases before so trying to get it booked into a workshop now i think its rod or main bearings i dont think it can be anything else now tbh
StevenMX
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StevenMX 8/1/2021 9:13pm
8/1/2021 9:13pm
FGR01 wrote:
What is the service spec for the rod axial play that you are measuring? That noise sounds like a bad rod bearing or main bearing to...
What is the service spec for the rod axial play that you are measuring?

That noise sounds like a bad rod bearing or main bearing to me. Has the bottom end ever been apart? How many hours on it?
Cammy41 wrote:
73 hours on it bottom end has never been apart, i dont know i cant find the spec in the manual
FGR01 wrote:
I don't have the 250 manual, but 0.75mm is the upper limit of the spec (0.45 - 0.75mm) for the 125/150. I'd assume the 250/300 is...
I don't have the 250 manual, but 0.75mm is the upper limit of the spec (0.45 - 0.75mm) for the 125/150. I'd assume the 250/300 is same or close. Is there any up/down play perceptible in the rod bearing? Do the rod and crank spin free, smooth, and tight by hand? That really sounds like lower rod bearing or main bearing noise to me.

This is from my 2021 KTM 250sx service manual...

0.60 - 0.70mm
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Cammy41
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Cammy41 8/2/2021 4:46am
8/2/2021 4:46am
Cammy41 wrote:
73 hours on it bottom end has never been apart, i dont know i cant find the spec in the manual
FGR01 wrote:
I don't have the 250 manual, but 0.75mm is the upper limit of the spec (0.45 - 0.75mm) for the 125/150. I'd assume the 250/300 is...
I don't have the 250 manual, but 0.75mm is the upper limit of the spec (0.45 - 0.75mm) for the 125/150. I'd assume the 250/300 is same or close. Is there any up/down play perceptible in the rod bearing? Do the rod and crank spin free, smooth, and tight by hand? That really sounds like lower rod bearing or main bearing noise to me.
StevenMX wrote:
[img]https://p.vitalmx.com/photos/forums/2021/08/01/503842/s1200_spec_ktm_250sx.jpg[/img] This is from my 2021 KTM 250sx service manual... 0.60 - 0.70mm

This is from my 2021 KTM 250sx service manual...

0.60 - 0.70mm
Thanks i couldnt find that anywhere in my manual
Appreciated
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walent215
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walent215 8/2/2021 5:10am
8/2/2021 5:10am
Cammy41 wrote:
73 hours on it bottom end has never been apart, i dont know i cant find the spec in the manual
FGR01 wrote:
I don't have the 250 manual, but 0.75mm is the upper limit of the spec (0.45 - 0.75mm) for the 125/150. I'd assume the 250/300 is...
I don't have the 250 manual, but 0.75mm is the upper limit of the spec (0.45 - 0.75mm) for the 125/150. I'd assume the 250/300 is same or close. Is there any up/down play perceptible in the rod bearing? Do the rod and crank spin free, smooth, and tight by hand? That really sounds like lower rod bearing or main bearing noise to me.
StevenMX wrote:
[img]https://p.vitalmx.com/photos/forums/2021/08/01/503842/s1200_spec_ktm_250sx.jpg[/img] This is from my 2021 KTM 250sx service manual... 0.60 - 0.70mm

This is from my 2021 KTM 250sx service manual...

0.60 - 0.70mm

Time to split the cases
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StevenMX
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StevenMX 8/2/2021 12:31pm
8/2/2021 12:31pm
Cammy41 wrote:
Thanks i couldnt find that anywhere in my manual
Appreciated
Happy to help Cammy... hopefully this sorts it out and you are back to riding in no time!
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Cammy41
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Cammy41 8/5/2021 11:43pm
8/5/2021 11:43pm
Split the cases and the main bearing on the ignition side is gone, thanks everyone
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FGR01
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FGR01 8/6/2021 7:48am
8/6/2021 7:48am
Rebuild the crank with a new rod kit while you are in there.
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OnTheCrossbar 10/17/2021 6:13pm
10/17/2021 6:13pm
Cammy41 wrote:
Split the cases and the main bearing on the ignition side is gone, thanks everyone
Crazy, I'm on my 5th 250sx. All were purchased new and did between 200-300hrs before sold. Never had to touch a bottom end.
sandman768
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sandman768 10/18/2021 6:04pm
10/18/2021 6:04pm
OnTheCrossbar wrote:
Crazy, I'm on my 5th 250sx. All were purchased new and did between 200-300hrs before sold. Never had to touch a bottom end.
I have had several 2t Ktm”s that were unbelievably reliable, no bottom end work at all. 1 of my XC 300”s had a crank bearing explode & take out cylinder, crank, top end ect. Bike had 40 hrs on it…. Ktm warrantied the parts… just luck of the draw…..
Cammy41
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Cammy41 10/19/2021 1:07pm
10/19/2021 1:07pm
sandman768 wrote:
I have had several 2t Ktm”s that were unbelievably reliable, no bottom end work at all. 1 of my XC 300”s had a crank bearing explode...
I have had several 2t Ktm”s that were unbelievably reliable, no bottom end work at all. 1 of my XC 300”s had a crank bearing explode & take out cylinder, crank, top end ect. Bike had 40 hrs on it…. Ktm warrantied the parts… just luck of the draw…..
Ive been unlucky with this 250 in lots of ways unfortunately
Its fixed now though 👍🏻

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