pay your respects - 23' YZ250 engine failure

maxer
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12/9/2020
Location
Grapevine, TX US
1/24/2023 1:03pm
nrosso391 wrote:
But here's the thing now one is talking about...this guy can fix this for around $500, based on the parts shown. Try to replace the same...

But here's the thing now one is talking about...this guy can fix this for around $500, based on the parts shown. Try to replace the same components on a Four-stroke and it will cost $2500+.

this is going to cost me almost $900

maxer
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12/9/2020
Location
Grapevine, TX US
1/24/2023 1:10pm
JK BRO wrote:

The engine didn't fail. C12/Pump w/stock compression, running lean ruined that engine.

No way that motor wasn't knocking like a solar salesman.

philG wrote:

I'd like this twice if i could. 

it really wasn’t knocking, i’m not sure. It’s very likely it was too lean but there wasn’t any ‘ warning signs ‘ like knocking or hanging idle etc. i linked a clip of what it sounded like right before it gave out and it was running sick on race day. i just pulled off after my moto and it was cutting out. then it wouldn’t start and compression was gone. thought i noticed a little lack of compression that weekend but after it gave out i could move the kick starter with my hand. it is what it is, expensive ass lesson learned 

zehn
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Location
Anchorage, AK US
1/24/2023 1:55pm
nrosso391 wrote:
But here's the thing now one is talking about...this guy can fix this for around $500, based on the parts shown. Try to replace the same...

But here's the thing now one is talking about...this guy can fix this for around $500, based on the parts shown. Try to replace the same components on a Four-stroke and it will cost $2500+.

Gary Duck wrote:
Your numbers are quite a bit off. Just sayin'        

Your numbers are quite a bit off. Just sayin'

Screenshot 2023-01-24 10.52.18 AM

 

 Screenshot 2023-01-24 11.07.37 AM

 Screenshot 2023-01-24 11.08.23 AM.png?VersionId=hBzlgD.xQMs4tNGxqz o

 

Also worth noting that such a catastrophic failure likely wouldn't have happened in a 4 stroke engine.

Another point is that service intervals for a 2 stroke top end are 10 hours, but far longer for a 4 stroke.

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kijen
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Location
Jacksonville, FL US
1/24/2023 3:38pm
kijen wrote:
While rebuilding recommend you measure your squish and get the head cut to preferred .050 or whatever it is, sure quite a few folks still do...

While rebuilding recommend you measure your squish and get the head cut to preferred .050 or whatever it is, sure quite a few folks still do this. We're running pump, with no issues with a pretty good rider and some flordia sand.

Jrey2 wrote:

Who did your head work?

My last one was PC, a few earlier was RB, but he is retired. Think Dicks racing, millinum technology, a few others. Some guys go bling and get head with inserts.  But getting the stock head is the same performance and cheaper.

The other suggestion to check your timing is key as well. Pretty easy to do once you get the tool. You may be auprised how off it is from the factory.

The Shop

crmx105
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5/7/2016
Location
Dunnellon, FL US
1/24/2023 3:53pm
JK BRO wrote:

The engine didn't fail. C12/Pump w/stock compression, running lean ruined that engine.

No way that motor wasn't knocking like a solar salesman.

philG wrote:

I'd like this twice if i could. 

maxer wrote:
it really wasn’t knocking, i’m not sure. It’s very likely it was too lean but there wasn’t any ‘ warning signs ‘ like knocking or hanging...

it really wasn’t knocking, i’m not sure. It’s very likely it was too lean but there wasn’t any ‘ warning signs ‘ like knocking or hanging idle etc. i linked a clip of what it sounded like right before it gave out and it was running sick on race day. i just pulled off after my moto and it was cutting out. then it wouldn’t start and compression was gone. thought i noticed a little lack of compression that weekend but after it gave out i could move the kick starter with my hand. it is what it is, expensive ass lesson learned 

YZ 250s can barely ping and be detonating. Most of the damage probably occurred before you started using C12 unless there is something else going on like previously mentioned. 

MxAddic
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Location
NY US
1/24/2023 4:29pm Edited Date/Time 1/24/2023 5:18pm

Bike was lean. No oil film visible in the transfers. I would call millennium.

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2
soggy
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3784
Joined
12/3/2018
Location
UT US
1/24/2023 4:34pm
JK BRO wrote:

The engine didn't fail. C12/Pump w/stock compression, running lean ruined that engine.

No way that motor wasn't knocking like a solar salesman.

philG wrote:

I'd like this twice if i could. 

maxer wrote:
it really wasn’t knocking, i’m not sure. It’s very likely it was too lean but there wasn’t any ‘ warning signs ‘ like knocking or hanging...

it really wasn’t knocking, i’m not sure. It’s very likely it was too lean but there wasn’t any ‘ warning signs ‘ like knocking or hanging idle etc. i linked a clip of what it sounded like right before it gave out and it was running sick on race day. i just pulled off after my moto and it was cutting out. then it wouldn’t start and compression was gone. thought i noticed a little lack of compression that weekend but after it gave out i could move the kick starter with my hand. it is what it is, expensive ass lesson learned 

Bikes usually do run pretty sick when they are on the lean side. Until they don’t. 

1/24/2023 4:36pm
philG wrote:

I'd like this twice if i could. 

maxer wrote:
it really wasn’t knocking, i’m not sure. It’s very likely it was too lean but there wasn’t any ‘ warning signs ‘ like knocking or hanging...

it really wasn’t knocking, i’m not sure. It’s very likely it was too lean but there wasn’t any ‘ warning signs ‘ like knocking or hanging idle etc. i linked a clip of what it sounded like right before it gave out and it was running sick on race day. i just pulled off after my moto and it was cutting out. then it wouldn’t start and compression was gone. thought i noticed a little lack of compression that weekend but after it gave out i could move the kick starter with my hand. it is what it is, expensive ass lesson learned 

crmx105 wrote:
YZ 250s can barely ping and be detonating. Most of the damage probably occurred before you started using C12 unless there is something else going on...

YZ 250s can barely ping and be detonating. Most of the damage probably occurred before you started using C12 unless there is something else going on like previously mentioned. 

Their also not big fans of ethanol fuels from my experiences at least. 

SEEMEFIRST
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Arlington, TX US
1/24/2023 5:00pm

Here's what pump gas, high compression detonation looks like.

20230124 185508 0.jpg?VersionId=Ogy2bg6J1TgRCuykB0veuhfrridTcT

 20230124 185749

 

3
1/24/2023 5:05pm
nrosso391 wrote:
But here's the thing now one is talking about...this guy can fix this for around $500, based on the parts shown. Try to replace the same...

But here's the thing now one is talking about...this guy can fix this for around $500, based on the parts shown. Try to replace the same components on a Four-stroke and it will cost $2500+.

Gary Duck wrote:
Your numbers are quite a bit off. Just sayin'        

Your numbers are quite a bit off. Just sayin'

Screenshot 2023-01-24 10.52.18 AM

 

 Screenshot 2023-01-24 11.07.37 AM

 Screenshot 2023-01-24 11.08.23 AM.png?VersionId=hBzlgD.xQMs4tNGxqz o

 

zehn wrote:
Also worth noting that such a catastrophic failure likely wouldn't have happened in a 4 stroke engine. Another point is that service intervals for a 2...

Also worth noting that such a catastrophic failure likely wouldn't have happened in a 4 stroke engine.

Another point is that service intervals for a 2 stroke top end are 10 hours, but far longer for a 4 stroke.

Damn, I need to service my top ends more 

BobPA
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PA US
1/24/2023 5:17pm
soggy wrote:

Bikes usually do run pretty sick when they are on the lean side. Until they don’t. 

PXL 20221219 225308161

 Lean is mean baby... 

4
soggy
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1/24/2023 5:28pm
soggy wrote:

Bikes usually do run pretty sick when they are on the lean side. Until they don’t. 

BobPA wrote:
 Lean is mean baby... 

PXL 20221219 225308161

 Lean is mean baby... 

Holy hell. 

2
1
zehn
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1/24/2023 5:41pm

Damn, I need to service my top ends more 

That's just going by the manual. I don't do top ends on our 2T at 10 hours believe me Laughing

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1
1/24/2023 5:57pm

Damn, I need to service my top ends more 

zehn wrote:
That's just going by the manual. I don't do top ends on our 2T at 10 hours believe me

That's just going by the manual. I don't do top ends on our 2T at 10 hours believe me Laughing

Oh good, I’m not sure what my manual says but I usually do 250s around 30 hours 

mattyhamz2
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7/6/2015
Location
So Cal, CA US
1/24/2023 8:03pm
nrosso391 wrote:
But here's the thing now one is talking about...this guy can fix this for around $500, based on the parts shown. Try to replace the same...

But here's the thing now one is talking about...this guy can fix this for around $500, based on the parts shown. Try to replace the same components on a Four-stroke and it will cost $2500+.

Gary Duck wrote:
Your numbers are quite a bit off. Just sayin'        

Your numbers are quite a bit off. Just sayin'

Screenshot 2023-01-24 10.52.18 AM

 

 Screenshot 2023-01-24 11.07.37 AM

 Screenshot 2023-01-24 11.08.23 AM.png?VersionId=hBzlgD.xQMs4tNGxqz o

 

zehn wrote:
Also worth noting that such a catastrophic failure likely wouldn't have happened in a 4 stroke engine. Another point is that service intervals for a 2...

Also worth noting that such a catastrophic failure likely wouldn't have happened in a 4 stroke engine.

Another point is that service intervals for a 2 stroke top end are 10 hours, but far longer for a 4 stroke.

Doesn’t the Kawi 450 manual say replace piston every 10-15 hours?

1
wrc777
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Greenwood, IN US
1/24/2023 10:22pm
mattyhamz2 wrote:

Doesn’t the Kawi 450 manual say replace piston every 10-15 hours?

Most Japanese bikes say that. 

1
MxAddic
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NY US
1/25/2023 12:06am
mattyhamz2 wrote:

Doesn’t the Kawi 450 manual say replace piston every 10-15 hours?

Yep, same for the oil, lol.

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1
1/25/2023 12:10am
mattyhamz2 wrote:

Doesn’t the Kawi 450 manual say replace piston every 10-15 hours?

wrc777 wrote:

Most Japanese bikes say that. 

Isn’t it ridiculous?!

im sure they say it so that if there’s a failure they’ll say: 

did you replace the piston at 15hrs? 
no? Well you should have done. 
 

or

did you replace the piston at 15hrs? 
yes? Well it must be mechanic’s error.

 

no warranty claim.

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1
PatH
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That One, PA US
1/25/2023 2:53am

C12 has a stoich of 14.79, E0 pump gas is 14.68 so C12 will not cause it to run lean. If you run it straight it will slow the flame front as it’s 112 Oct.  

 

T2 is oxygenated so it will cause it to run lean. T2 stoich is 13.5 so jetting changes would be needed.  
 

something else going on here because there’s no reason it should have had pre ignition and or detonation with C12/pump unless it was pulling air from somewhere it wasn’t supposed to. 

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1
wrc777
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1/25/2023 4:28am
mattyhamz2 wrote:

Doesn’t the Kawi 450 manual say replace piston every 10-15 hours?

wrc777 wrote:

Most Japanese bikes say that. 

Isn’t it ridiculous?! im sure they say it so that if there’s a failure they’ll say:  did you replace the piston at 15hrs?  no? Well you...

Isn’t it ridiculous?!

im sure they say it so that if there’s a failure they’ll say: 

did you replace the piston at 15hrs? 
no? Well you should have done. 
 

or

did you replace the piston at 15hrs? 
yes? Well it must be mechanic’s error.

 

no warranty claim.

I do t know how kawi and Yamaha are but Honda says no warranty period so I don’t think they are hiding behind that 15 hour change interval.
 

Ktm says 45 hours on the 2023 4 strokes. 

1
jpatz319
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Statesville, NC US
1/25/2023 5:04am

I had my '22 250 blew up with 12.5 hours due to the power valve shaft broke in half.  Stuff happens with new bikes sometimes. 

1/25/2023 5:20am
Whoever rebuilds that motor have them check the ignition timing with a degree wheel and make sure its on point.  We had a few 23' YZ250's...

Whoever rebuilds that motor have them check the ignition timing with a degree wheel and make sure its on point.  We had a few 23' YZ250's up here in CT that were banging out of the box on straight C12..timing was off on them.  May not be the case here but it would not hurt to do it.

Good luck-J

Jrey2 wrote:
My 21 has been a little knock prone out of the box. It was angry in FL at high load/temp as well. is there a rule...

My 21 has been a little knock prone out of the box. It was angry in FL at high load/temp as well. is there a rule of thumb on jetting for colder weather you'd be willing to share?

The rule of thumb for jetting a carb in a 2 stroke in colder temps for what I have done is go up on jetting until you hit the “wall” with a dark plug and it’s rich, then back it down a notch and you are good.

it’s all about the plug color and I also run mine a hair rich to be safe, I would rather deal with a small amount of a rich condition over a rebuild any day of the week!

 

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1/25/2023 5:44am
PatH wrote:
C12 has a stoich of 14.79, E0 pump gas is 14.68 so C12 will not cause it to run lean. If you run it straight it...

C12 has a stoich of 14.79, E0 pump gas is 14.68 so C12 will not cause it to run lean. If you run it straight it will slow the flame front as it’s 112 Oct.  

 

T2 is oxygenated so it will cause it to run lean. T2 stoich is 13.5 so jetting changes would be needed.  
 

something else going on here because there’s no reason it should have had pre ignition and or detonation with C12/pump unless it was pulling air from somewhere it wasn’t supposed to. 

PatH- I’m glad you brought this up as I have a question about this.

If comparing fuels, the 5.7% oxygen content in T4/T2, (no ethanol but most likely a nitro oxygenator), as compared to ethanol 93 pump (4% oxygen), do you feel that the 1.7% increase is enough to have the engine run that lean?

I am in the middle of a heavy discussion over this with a certain bike mfg over the fuel debate and it’s getting concerning.

please post back your thoughts on this, I could use some more feedback.

DM me if you want as not to side track this post.

thx-

1
PatH
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That One, PA US
1/25/2023 6:08am
PatH wrote:
C12 has a stoich of 14.79, E0 pump gas is 14.68 so C12 will not cause it to run lean. If you run it straight it...

C12 has a stoich of 14.79, E0 pump gas is 14.68 so C12 will not cause it to run lean. If you run it straight it will slow the flame front as it’s 112 Oct.  

 

T2 is oxygenated so it will cause it to run lean. T2 stoich is 13.5 so jetting changes would be needed.  
 

something else going on here because there’s no reason it should have had pre ignition and or detonation with C12/pump unless it was pulling air from somewhere it wasn’t supposed to. 

PatH- I’m glad you brought this up as I have a question about this. If comparing fuels, the 5.7% oxygen content in T4/T2, (no ethanol but...

PatH- I’m glad you brought this up as I have a question about this.

If comparing fuels, the 5.7% oxygen content in T4/T2, (no ethanol but most likely a nitro oxygenator), as compared to ethanol 93 pump (4% oxygen), do you feel that the 1.7% increase is enough to have the engine run that lean?

I am in the middle of a heavy discussion over this with a certain bike mfg over the fuel debate and it’s getting concerning.

please post back your thoughts on this, I could use some more feedback.

DM me if you want as not to side track this post.

thx-

E10 is roughly 3.5-4% oxygen, would the 1.5-2% cause it to be lean? Well that depends on how the tuning is on E0, as I am sure you are aware there is a fine line where where the burn goes from ideal to Lean.  Rich is much more forgiving.  The other factor to the equation is how close the CDI is tuned for timing to the edge.  I can tell you it is my opinion that my 23 300sx is fairly conservative from KTM on timing, now I am sure the 205psi cyl pressure is part of that reason but I find even playing with plug heat ranges the plug never shows timing to be aggressive at all.  Again, this is with my limited testing so far and no good weather.  At some point in the near future the plan is to get it on my cousins dyno and do a bunch of testing.  Currently with no available way to tune the bike so I plan to do some experimenting with adding oxygenated fuel to the mix to get the AFR to a sweet spot.  

Fireblade2k
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10/31/2019
Location
Saint Petersburg, FL US
1/25/2023 6:45am

Powerseal USA or millennium will get that cylinder back to new condition for less than $300 shipped. 

1
1/25/2023 1:53pm

Something very amiss here.

1. Piston has zero wash. Either this thing is incredibly lean turning the oil into carbon immediately, or it is sucking trans fluid.

2. That does not look like Motul 800 in the many engines I've seen, or it is ridden so slow and cold (combustion temps) it is carboning everything up and not burning off the oil film.

This can happen with any oil, but most especially higher flash point oil say 450F and up.   

Further, I've seen kart engines ran with pure Castor look completely clean in comparison to the topic enging pics with Castrol R30/R40, the discontinued old Maxima Degummed racing Castor, Klotz Green label Benol or Blendzall Green Label.

"It was running great" 

They always run best right before they blow. 

C12 technically should run colder combustion temps all else being equal, but not so much to carbon everything up.

Hard to gauge without EGTs.

Happen to have pics of the pipe/silencer?  C12 should have a whitish grey ashy outlet(that is the TEL in the fuel)

Even at 50/50, that would be ~2 grams per gallon, same as 100LL. Pipe should look similar.

 

4
1/25/2023 2:07pm
zehn wrote:
Also worth noting that such a catastrophic failure likely wouldn't have happened in a 4 stroke engine. Another point is that service intervals for a 2...

Also worth noting that such a catastrophic failure likely wouldn't have happened in a 4 stroke engine.

Another point is that service intervals for a 2 stroke top end are 10 hours, but far longer for a 4 stroke.

LOL. Actually, 2 stroke top ends can go 400 hours plus at times depending on use.......but not at these crazy lean ratios people want to run. ie "My 85 Exoert kid runs Xxxx oil at 80:1 and it needs a new top end every 6 hours and a crank at 10."  Yeah, because it is dry.

We have ran engines till they didn't have enough compression anymore to start. And that takes a ton of hours.

5
ss-racing
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8/31/2018
Location
Raleigh, NC US
1/25/2023 5:26pm

I'd pressure test that motor before I ran it again .  The detonation is obvious, but it shouldn't  be detonating that bad unless it had previously been jetted for say, summer in Denver. (90 degrees, and 5500' elevation) .  Could also be ignition , or maybe it lacked coolant.  

Also, thoroughly check the carb, maybe the PowerJet is plugged or something

 

3
1/25/2023 5:48pm
Whoever rebuilds that motor have them check the ignition timing with a degree wheel and make sure its on point.  We had a few 23' YZ250's...

Whoever rebuilds that motor have them check the ignition timing with a degree wheel and make sure its on point.  We had a few 23' YZ250's up here in CT that were banging out of the box on straight C12..timing was off on them.  May not be the case here but it would not hurt to do it.

Good luck-J

Jrey2 wrote:
My 21 has been a little knock prone out of the box. It was angry in FL at high load/temp as well. is there a rule...

My 21 has been a little knock prone out of the box. It was angry in FL at high load/temp as well. is there a rule of thumb on jetting for colder weather you'd be willing to share?

The rule of thumb for jetting a carb in a 2 stroke in colder temps for what I have done is go up on jetting until...

The rule of thumb for jetting a carb in a 2 stroke in colder temps for what I have done is go up on jetting until you hit the “wall” with a dark plug and it’s rich, then back it down a notch and you are good.

it’s all about the plug color and I also run mine a hair rich to be safe, I would rather deal with a small amount of a rich condition over a rebuild any day of the week!

 

I go up until it blubbers on top end and then back down 2 sizes.

JM485
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5022
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10/1/2013
Location
Davis, CA US
1/25/2023 6:20pm
Gary Duck wrote:
Your numbers are quite a bit off. Just sayin'        

Your numbers are quite a bit off. Just sayin'

Screenshot 2023-01-24 10.52.18 AM

 

 Screenshot 2023-01-24 11.07.37 AM

 Screenshot 2023-01-24 11.08.23 AM.png?VersionId=hBzlgD.xQMs4tNGxqz o

 

zehn wrote:
Also worth noting that such a catastrophic failure likely wouldn't have happened in a 4 stroke engine. Another point is that service intervals for a 2...

Also worth noting that such a catastrophic failure likely wouldn't have happened in a 4 stroke engine.

Another point is that service intervals for a 2 stroke top end are 10 hours, but far longer for a 4 stroke.

mattyhamz2 wrote:

Doesn’t the Kawi 450 manual say replace piston every 10-15 hours?

Where is the guy who used to be shocked that anyone would run a piston past 10 hours on any bike?Laughing

3

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