yz250 engine problem

zac_k3
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TN US
4/2/2020 7:43am Edited Date/Time 4/2/2020 12:27pm
My friend picked up a 2006 yz250 and was told the bike had 3 hours on a top and bottom end. Got the bike home, rode it 3 laps on his home track, parked it and then came back to it not kicking over. At first glance we thought the bike was locked up but after pulling the cylinder everything turned over freely. Could a ring be getting stuck? Also wondering what this hot spot on the crank could be coming from and is it safe to use. Thanks!

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4/2/2020 8:09am
The hotspot on the crank is from the factore when they are installing the big end. I dont know about the locking up.
kb228
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4/2/2020 8:15am
Looks like more than 3 hours on that piston to me. Where are the rings?
1
zac_k3
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4/2/2020 8:31am
kb228 wrote:
Looks like more than 3 hours on that piston to me. Where are the rings?
we wanted to put the cylinder back on to see if the engine would continue to turnover or if it would get stuck again so we just pulled them off to make it easier.
mwmx54
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Pleasant Grove, UT US
4/2/2020 9:25am
I’d atleast put new rings on, especially if you didn’t keep track of the orientation of the ones you removed. make sure you gap the rings as well. That piston doesn’t look 3 hours old, you may be wise to replace the whole deal. Crank looks fine, if the rod were burned, then you’d need to worry, just check it for up/down play.

The Shop

DynoDan22
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Victorville, CA US
4/2/2020 9:31am
Could you take a few more pics of the piston/head/cylinder to rule out a top end seizure?
zac_k3
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4/2/2020 10:11am Edited Date/Time 4/2/2020 10:11am
DynoDan22 wrote:
Could you take a few more pics of the piston/head/cylinder to rule out a top end seizure?
I believe he’s going to get it honed but we didn’t feel any scratches or anything.


zac_k3
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4/2/2020 10:13am
mwmx54 wrote:
I’d atleast put new rings on, especially if you didn’t keep track of the orientation of the ones you removed. make sure you gap the rings...
I’d atleast put new rings on, especially if you didn’t keep track of the orientation of the ones you removed. make sure you gap the rings as well. That piston doesn’t look 3 hours old, you may be wise to replace the whole deal. Crank looks fine, if the rod were burned, then you’d need to worry, just check it for up/down play.
Yeah he’s going to do a new top end just to get rid of the shitty namura piston and freshen it up and the crank feels solid besides being a hot rods lol.
kb228
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4/2/2020 10:32am
mwmx54 wrote:
I’d atleast put new rings on, especially if you didn’t keep track of the orientation of the ones you removed. make sure you gap the rings...
I’d atleast put new rings on, especially if you didn’t keep track of the orientation of the ones you removed. make sure you gap the rings as well. That piston doesn’t look 3 hours old, you may be wise to replace the whole deal. Crank looks fine, if the rod were burned, then you’d need to worry, just check it for up/down play.
zac_k3 wrote:
Yeah he’s going to do a new top end just to get rid of the shitty namura piston and freshen it up and the crank feels...
Yeah he’s going to do a new top end just to get rid of the shitty namura piston and freshen it up and the crank feels solid besides being a hot rods lol.
The namura piston is probably the problem. Chinese junk right there.
1
Tracktor
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The RTF/Amboy, WA US
4/2/2020 11:30am
mwmx54 wrote:
I’d atleast put new rings on, especially if you didn’t keep track of the orientation of the ones you removed. make sure you gap the rings...
I’d atleast put new rings on, especially if you didn’t keep track of the orientation of the ones you removed. make sure you gap the rings as well. That piston doesn’t look 3 hours old, you may be wise to replace the whole deal. Crank looks fine, if the rod were burned, then you’d need to worry, just check it for up/down play.
zac_k3 wrote:
Yeah he’s going to do a new top end just to get rid of the shitty namura piston and freshen it up and the crank feels...
Yeah he’s going to do a new top end just to get rid of the shitty namura piston and freshen it up and the crank feels solid besides being a hot rods lol.
kb228 wrote:
The namura piston is probably the problem. Chinese junk right there.
Beat me to it! Namura is Grade A shit.............
Matt Fisher
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4/2/2020 12:27pm
zac_k3 wrote:
Yeah he’s going to do a new top end just to get rid of the shitty namura piston and freshen it up and the crank feels...
Yeah he’s going to do a new top end just to get rid of the shitty namura piston and freshen it up and the crank feels solid besides being a hot rods lol.
kb228 wrote:
The namura piston is probably the problem. Chinese junk right there.
Tracktor wrote:
Beat me to it! Namura is Grade A shit.............
Agreed. Their tagline should read: "Namura- garbage in the shape of a piston"

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