Ktm 250 sx Bottom End longevity

moto12356999
Edited Date/Time 9/4/2022 3:06am
Hi, I’ve got a 90 hour 2018 250 sx, nearing the end of the season here in UK. Wondering whether I’ll get away with refreshing just the top end assuming no play in rod?

Impossible to answer with any real certainty, but on a limited budget & need to be economical as possibly with my racing these days, I’m Vet expert, bike has had 3 pistons evenly spaced over the 90 hours, runs & rides like it should.

Anyone have an experience on wear of the bottom
End & advice on when approx it should be done for a not pro, but fast vet rider ?

Thanks
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insertinfo 9/3/2022 7:56am
9/3/2022 7:56am
Had a 2019 (same engine). Sold it at 105 hrs with 1 top end done. It had no problems.
A friend had a tc 19 (same engine) and had a rod bearing failure at 120 hrs.
Another friend had a 18 like yours and sold it at 160 hours with 2 top ends.
If you rip it hard i would say do also the bottom end.

Also, which % ratio did you run it? Which oil?
I used to use motul800 @3% (33:1)
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insertinfo 9/3/2022 7:58am
9/3/2022 7:58am
Bike was awesome but it was a bull to ride. I'm 57kg tho.

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OnTheCrossbar 9/3/2022 9:14am
9/3/2022 9:14am
moto12356999 wrote:
Hi, I’ve got a 90 hour 2018 250 sx, nearing the end of the season here in UK. Wondering whether I’ll get away with refreshing just...
Hi, I’ve got a 90 hour 2018 250 sx, nearing the end of the season here in UK. Wondering whether I’ll get away with refreshing just the top end assuming no play in rod?

Impossible to answer with any real certainty, but on a limited budget & need to be economical as possibly with my racing these days, I’m Vet expert, bike has had 3 pistons evenly spaced over the 90 hours, runs & rides like it should.

Anyone have an experience on wear of the bottom
End & advice on when approx it should be done for a not pro, but fast vet rider ?

Thanks
In amongst other bikes, ive had an 08, 11, 13, 17, and now a 21. Vet Expert now. Ive never done more than piston and rings, the highest hour was my 13 with close to 300hrs.
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Factor E
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Factor E 9/3/2022 9:15am
9/3/2022 9:15am
Full bottom end
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moto12356999 9/3/2022 10:38am
9/3/2022 10:38am
Thanks for the info guys, I may try get it though another season with it then.
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moto12356999 9/3/2022 10:40am
9/3/2022 10:40am
Thisusernameisavailable wrote:
You’re doing a piston every 30 hrs on a 250??

You coulda got away with one!
That’s fair enough, I bought the bike used at 44 hours, when I did the piston for the first time I realised the previous owner had already done one. I wasn’t to know until opening it. Prob could have easily been 2 pistons over 90 hours.
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Not-a-Fan
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Not-a-Fan 9/3/2022 12:08pm
9/3/2022 12:08pm Edited Date/Time 9/3/2022 12:12pm
I wouldn't even consider a bottom end until 150+ personally. I think you did the right thing on the piston, they're still cast so better safe than sorry but the bottom ends are pretty bullet proof. There are only occasional failures and to me they were defective from the start, its not the norm. You can have them rebuilt better than new by cooksey cranks, he will true it up to razor thin run out measurements and will rebuild with prox or oem rods for good price

Nvm, cooksey won't work didn't realize you were in the UK.
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rjg
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rjg 9/3/2022 2:08pm
9/3/2022 2:08pm
I went over 500 hours on 2014 250sx bottom end. You do t need to touch it.
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Not-a-Fan
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Not-a-Fan 9/3/2022 4:13pm
9/3/2022 4:13pm Edited Date/Time 9/3/2022 4:14pm
rjg wrote:
I went over 500 hours on 2014 250sx bottom end. You do t need to touch it.
Mx with sustained high rpm or more trail with low to mid rpm? 500hrs seems crazy but one thing i do know is we definitely tend to throw things out before they're worn in this sport. A lot of it is just for peace of mind though cause nobody wants that shit locking up on a jump face, just a disaster that i don't want to experience. The main thing is cooksey will rebuild it for $240 for up to the 2016 and $280 for a newer models so its hard to justify taking the gamble for me personally. My insurance deductible is way higher than $300 Laughing
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AJ565
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AJ565 9/3/2022 4:16pm
9/3/2022 4:16pm
I have 120ish hours all MX on my 2018 250sx with the stock bottom end. I did a piston at 90 hours, not because it needed it.
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moto12356999 9/4/2022 2:29am
9/4/2022 2:29am
AJ565 wrote:
I have 120ish hours all MX on my 2018 250sx with the stock bottom end. I did a piston at 90 hours, not because it needed...
I have 120ish hours all MX on my 2018 250sx with the stock bottom end. I did a piston at 90 hours, not because it needed it.
That’s good to know, what level of rider are you ?
CPR
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CPR 9/4/2022 3:06am
9/4/2022 3:06am
Dirt is the main enemy of a two banger bottom end. If you’re meticulous with your air filter, you should be able to just do the top end and keep ripping.
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